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Tumor Shrinking Triple Helices

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Tumor-Shrinking Triple-Helices

A braided structure and some adhesive hydrogel make therapeutic microRNAs both stable and sticky.

By Ruth Williams | April 1, 2016

http://www.the-scientist.com/?articles.view/articleNo/45576/title/Tumor-Shrinking-Triple-Helices

 

MicroRNAs (miRs) are small, noncoding ribonucleic acids that control the translation of target messenger RNAs (mRNAs). Given their roles in development, differentiation, and other cellular processes, misregulation of miRs can contribute to diseases such as cancer. Indeed, “they are recognized as important modulators of cancer progression,” says Natalie Artzi of Harvard Medical School.

In addition to occasionally promoting cancer pathology, miRs also hold the potential to treat it—either by restoring levels of suppressed miRs, or by repressing overactive ones using antisense miRs (antagomiRs). While miRs are promising therapeutic molecules, says Daniel Siegwart of the University of Texas Southwestern Medical Center in Dallas, their use “is currently hindered by at least two issues: nucleic acid instability in vivo, and the development of effective delivery systems to transport miRs into tumor cells.”

Artzi and her team have now addressed both of these issues in one fell swoop. They first assembled two therapeutic miRs—one antagomiR and one that replaced a deficient miR—together with a third miR, a complement of the replacement strand, into triple-helix structures, which increased molecular stability without affecting function. They then complexed these helices with dendrimers—large synthetic branching polymer particles—and mixed these complexes with dextran aldehyde to form an adhesive hydrogel. The gel could then be applied directly to the surface of tumors to deliver the therapeutic miRs into cells with high efficiency.

In mice with induced breast tumors, the triple-helix–hydrogel approach led to dramatic tumor shrinkage and extended life span: the animals survived approximately one month longer than those treated with standard-of-care chemotherapy drugs. Because the RNA-hydrogel mixture must be applied directly to the tumor, the approach will not be suitable for all cancers. But one potential application, says Siegwart, is that “the hydrogel could be applied by a surgeon after performing bulk tumor removal…[and] might kill remaining tumor cells that would otherwise cause tumor recurrence.” (Nature Materials, http://dx.doi.org:/10.1038/NMAT4497, 2015)

STICKING IT TO TUMORS: To deliver therapeutic microRNAs (miRs) to tumors, braids of three microRNAs (miRs)—an antisense strand that blocks a miR overactive in cancer, a strand that replaces a deficient miR, and a stabilizing strand (1)—are added to a dendrimer (2) and mixed with a hydrogel scaffold (3). When researchers introduced the sticky gel onto mouse mammary tumors (4), the malignancies shrank and the animals lived longer (5)© GEORGE RETSECK; J.CONDE ET AL., NATURE MATERIALS

 

miR DELIVERY SYSTEM VEHICLE DOSE TUMOR TARGETING APPLICABLE TUMOR TYPES
Nanoparticles Examples: gold particles, liposomes, peptide nucleic acids, or polymers Usually multiple injections Combining miRs with aptamers or antibodies can guide nanoparticles to target cells, but systemic delivery inevitably leads to some off-target dispersion. Multisite or blood cancers
RNA–triple-helix-hydrogel Dendrimer-dextran hydrogel One Adhesive hydrogel sticks miRs to tumor site with minimal dispersion to other tissues. Solid Tumors

 

Self-assembled RNA-triple-helix hydrogel scaffold for microRNA modulation in the tumour microenvironment

João CondeNuria OlivaMariana AtilanoHyun Seok Song & Natalie Artzi
Nature Materials15,353–363(2016)
                         http://dx.doi.org:/10.1038/nmat4497

The therapeutic potential of miRNA (miR) in cancer is limited by the lack of efficient delivery vehicles. Here, we show that a self-assembled dual-colour RNA-triple-helix structure comprising two miRNAs—a miR mimic (tumour suppressor miRNA) and an antagomiR (oncomiR inhibitor)—provides outstanding capability to synergistically abrogate tumours. Conjugation of RNA triple helices to dendrimers allows the formation of stable triplex nanoparticles, which form an RNA-triple-helix adhesive scaffold upon interaction with dextran aldehyde, the latter able to chemically interact and adhere to natural tissue amines in the tumour. We also show that the self-assembled RNA-triple-helix conjugates remain functional in vitro and in vivo, and that they lead to nearly 90% levels of tumour shrinkage two weeks post-gel implantation in a triple-negative breast cancer mouse model. Our findings suggest that the RNA-triple-helix hydrogels can be used as an efficient anticancer platform to locally modulate the expression of endogenous miRs in cancer.

 

Figure 1: Self-assembled RNA-triple-helix hydrogel nanoconjugates and scaffold for microRNA delivery.

Self-assembled RNA-triple-helix hydrogel nanoconjugates and scaffold for microRNA delivery.

a, Schematic showing the self-assembly process of three RNA strands to form a dual-colour RNA triple helix. The RNA triplex nanoparticles consist of stable two-pair FRET donor/quencher RNA oligonucleotides used for in vivo miRNA inhibit…

 

Figure 4: Proliferation, migration and survival of cancer cells as a function of RNA-triple-helix nanoparticles treatment.close

Proliferation, migration and survival of cancer cells as a function of RNA-triple-helix nanoparticles treatment.

a, miR-205 and miR-221 expression in breast cancer cells at 24, 48 and 72h of incubation (n = 3, statistical analysis performed with a two-tailed Students t-test, , P < 0.01). miRNA levels were normalized to the RNU6B reference gene

 

  1. Kasinski, A. L. & Slack, F. J. MicroRNAs en route to the clinic: Progress in validating and targeting microRNAs for cancer therapy. Nature Rev. Cancer 11, 849864 (2011).
  2. Li, Z. & Rana, T. M. Therapeutic targeting of microRNAs: Current status and future challenges. Nature Rev. Drug Discov. 13, 622638 (2014).
  3. Yin, H. et al. Non-viral vectors for gene-based therapy. Nature Rev. Genet. 15, 541555(2014).
  4. Conde, J., Edelman, E. R. & Artzi, N. Target-responsive DNA/RNA nanomaterials for microRNA sensing and inhibition: The jack-of-all-trades in cancer nanotheranostics? Adv. Drug Deliv. Rev. 81, 169183 (2015).
  5. Chen, Y. C., Gao, D. Y. & Huang, L. In vivo delivery of miRNAs for cancer therapy: Challenges and strategies. Adv. Drug Deliv. Rev. 81, 128141 (2015).
  6. Yin, P. T., Shah, B. P. & Lee, K. B. Combined magnetic nanoparticle-based microRNA and hyperthermia therapy to enhance apoptosis in brain cancer cells. Small 10, 41064112(2014).
  7. Hao, L. L., Patel, P. C., Alhasan, A. H., Giljohann, D. A. & Mirkin, C. A. Nucleic acid–gold nanoparticle conjugates as mimics of microRNA. Small 7, 31583162 (2011).
  8. Endo-Takahashi, Y. et al. Systemic delivery of miR-126 by miRNA-loaded bubble liposomes for the treatment of hindlimb ischemia. Sci. Rep. 4, 3883 (2014).
  9. Chen, Y. C., Zhu, X. D., Zhang, X. J., Liu, B. & Huang, L. Nanoparticles modified with tumor-targeting scFv deliver siRNA and miRNA for cancer therapy. Mol. Ther. 18, 16501656(2010).
  10. Anand, S. et al. MicroRNA-132-mediated loss of p120RasGAP activates the endothelium to facilitate pathological angiogenesis. Nature Med. 16, 909914 (2010).

 

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Targeting Neuronal Cell Growth

Larry H. Bernstein, MD, FCAP, Curator

LPBI

 

Remote Mind Control

Using chemogenetic tools to spur the brain into action

By Kelly Rae Chi | November 1, 2015     http://www.the-scientist.com//?articles.view/articleNo/44321/title/Remote-Mind-Control/

http://www.the-scientist.com/November2015/LT_2_opener.jpg

A MATTER OF TIME: Optogenetics methods, which work on the millisecond timescale, allow for the finest level of temporal control over neuron excitation and inhibition. The chemogenetic tools, DREADDs and PSAMs-PSEMs, are ideal for the study of longer-lasting behaviors such as appetite, thirst, or anxiety because they work over a scale of the minutes-to-hours. The receptors are incorporated into specific neurons or cells using viruses. Ligands—CNO or salvinorin B (for DREADD receptors) or PSEMs—are administered via injection or drinking water. Both receptors and ligands are orthogonal, meaning they do not bind to anything else in the body.
REDRAWN WITH PERMISSION OF SCOTT STERNSON FROM SCIENCE, 333:1292, 2011; NEUROENDOCRINOLOGY, 100:98, 2014

In a pharmacology lab at the University of North Carolina at Chapel Hill, doctoral student Reid Olsen, working with brain tissue harvested from a mouse just a few hours earlier, readies half a dozen dime-size slices for live calcium imaging. This mouse’s brain contains a genetically engineered receptor that Olsen has targeted to cells thought to control the making of new neurons in adult mice. He is about to use a synthetic drug to activate this receptor in the tissue. When it indeed works—just as he has predicted—he turns his attention to attempting to stimulate neurogenesis in a freely moving mouse that has the same engineered receptors in its brain.

Less than a decade ago, such precise control over neuronal activity in a dish, let alone in a living brain, was impossible. The drugs available to repress neurons or encourage them to fire would produce off-target effects or eliminate cell populations indiscriminately.

Working in the lab of Juan Song, Olsen is using a “designer receptor exclusively activated by a designer drug,” or DREADD. These modified G protein–coupled receptors (GPCRs) are usually either virally administered or bred into animals, then activated by a specific ligand that’s either injected or taken orally. Both the receptor and the ligand are designed to be orthogonal, effectively meaning they bind to each other but to nothing else.

Along with DREADDs, recently developed orthogonal ligand-gated ion channels called “pharmacologically selective actuator molecules” and “pharmacologically selective effector molecules” (PSAMs-PSEMs), are allowing researchers to dial up or dial down neuronal activity in living animals, with the goal of clarifying the brain wiring that controls appetite, thirst, anxiety, and many other behaviors.

Along with DREADDs, recently developed orthogonal ligand-gated ion channels called “pharmacologically selective actuator molecules” and “pharmacologically selective effector molecules” (PSAMs-PSEMs), are allowing researchers to dial up or dial down neuronal activity in living animals, with the goal of clarifying the brain wiring that controls appetite, thirst, anxiety, and many other behaviors.

“[DREADDs and PSAMs–PSEMs] are completely complementary methods, and they can in principle be used together in the same animal.—Scott Sternson, HHMI Janelia Research Campus”

These are not the only so-called chemical genetic, or “chemogenetic,” tools for controlling cells. Orthogonal kinases have been used in the brain to deduce the mechanisms underlying epilepsy, memory, and neuronal development. And inducible genetic systems, now in wide use for two decades—for example, tetracycline-dependent transcriptional promoters—are incredibly powerful for expressing specific genes at a particular point in an animal’s development, says Bruce Conklin, senior investigator at the University of California, San Francisco–affiliated Gladstone Institute of

Cardiovascular Disease, whose group pioneered the development of engineered GPCRs. At the other extreme of temporal control from inducible genetic systems, optogenetics—a set of methods that use light to activate genetically encoded opsins—is widely used for controlling brain cells on the millisecond time scale in vivo.

As tools, DREADDs and PSAMs-PSEMs allow control of neuronal activity over a middle ground—from minutes to hours. “These are the time scales that are most useful, in my opinion, for neurobiology experiments,” says Scott Sternson of the Howard Hughes Medical Institute’s Janelia Research Campus in Ashburn, Virginia, who has developed PSAMs-PSEMs but who also regularly uses DREADDs and optogenetics. (For a review, see Ann Rev Neurosci, 37:387-407, 2014.)

The Scientist talked to developers about the basics behind DREADDs and PSAMs-PSEMs. Here’s what they said.

DREADDs and PSAMs-PSEMs: A history

In 1991, scientists showed that engineering orthogonal GPCRs was possible, and first iterations of such tools, dubbed “receptor activated solely by a synthetic ligand”  or RASSLs, came onto the scene in 1998.

Bryan Roth, of the UNC School of Medicine, made the second generation of RASSLs, which he called DREADDs, using an engineered muscarinic GPCR and, importantly, a ligand that was chemically inert (PNAS, 104:5163-68, 2007). Since the publication of that first paper on DREADDs, hundreds of labs have administered them in vivo, Roth says. This chemical genetic technique has the advantage of being easier to implement and less invasive than optogenetics, he adds.

Ligand-gated ion channel–based chemical genetic tools have their own history, but were not used in vivo in animals until 2011, when Sternson developed PSAMs-PSEMs. The researchers mutated ligand-binding domains and mixed and matched them to different ion-pore domains. But they altered the receptors and their ligands further so that they don’t interact with anything in the body. “As I was thinking about that system, I imagined I would want it to have easily optimizable, nontoxic ligands and the ability to tune the ion[-pore] or ligand-binding domain easily,” Sternson says.

DREADDs and PSAM-PSEM combinations in action

There are five different classes of DREADDs available, each designed for a different purpose:

  • hM3Dq raises calcium levels in a cell, causing burst firing;
  • hM4Di lowers cAMP and the activation of a particular potassium channel, causing neuronal silencing; also inhibits presynaptic neurotransmitter release;
  • GsD enhances cAMP, causing modulation signaling;
  • Rq(R165L) enhances arrestin signaling, a specific pathway that has been linked to the mechanisms of psychoactive drugs;
  • κ-opioid receptor DREADD or  KORD quiets neurons and also inhibits presynaptic neurotransmitter release.

The synthetic ligand for each of the first four DREADDs is clozapine-N-oxide (CNO), whereas KORDs are activated by salvinorin B. That means combining DREADDs is now possible: Roth’s group showed recently that they could insert the hM3Dq and KORD to be able to activate and silence the same neurons (Neuron, 86:936-46, 2015).

Roth’s lab has also made light-activated (photocaged) CNO, which allows for more-precise control over the timing of DREADD receptor activation. He has not published any papers using this yet, but will provide the caged ligand to interested researchers upon request. To make use of photocaged CNO, however, you will need to surgically implant an optic cable to provide light to the brain region of interest. If you’re going to go to the trouble, you might consider optogenetics, Roth adds.

Scientists have paired different PSAMs with various ion channels and PSEMs in order to control neurons. Among the most popular:

  • PSAML141F, Y115F– 5HT3 HC is activated by the ligand PSEM89S, allowing cations to flow into the cell and boost excitability;
  • PSAML141F, Y115F – GlyR is activated by the ligand PSEM89S, silencing neurons;
  • PSAMQ79G, L141S-nAChR V13 is activated by the ligand PSEM9S, enhancing calcium signaling. (Because there are two different PSEM ligands, PSAMs-PSEMs can also be combined in the same animal.)

When to opt for optogenetics

The single biggest consideration in your choice of, and among, these technologies is the temporal control needed for your experiment. Optogenetics, for example, offers the finest level of control, on the order of milliseconds to seconds. If you’re examining decision-making behaviors, for example, then optogenetics (or electrical stimulation) is for you.

If you’re studying behaviors—such as eating or drinking—or physiological changes that occur over minutes to hours, then either optogenetics, chemogenetics, or both might work.

For long-lasting behaviors being measured over the course of hours to days, a chemogenetic approach such as DREADDs or PSAMs-PSEMs is the clear winner. The ligands linger longer than short light pulses and can even be dissolved into the animals’ drinking water. The chemogenetic approach is also superior for investigating larger swaths of brain, which are challenging to illuminate using optogenetics methods, Roth says.

Researchers have also successfully combined the approaches, typically using an optogenetic approach to turn on neurons and chemogenetic approaches to switch them off in the same animal. The inhibitory DREADD hM4Di targets presynaptic terminals, which could be especially helpful if you’re investigating a region of the brain where long-range projection neurons terminate.

Use DREADDs or PSAMs-PSEMs first?

TWOFERS: In 2015, researchers announced a new DREADD: KORD. Because it is activated by a different ligand than the one for previously developed DREADDs, the engineered receptors can now be combined in the same animal. BRYAN ROTH

Researchers tend to start with DREADDs simply because they have been around longer, Sternson says. But some will turn to PSAMs if DREADDs have been ineffective. “Most cell types will respond to [DREADDs] as they’re supposed to, but not all,” Sternson says. That’s because DREADDs tap into a complex signaling pathway that eventually results in neuronal activation or silencing. In contrast, PSAMs work by controlling the gating of an ion channel. On the other hand, ligand-gated ion channels may affect some types of cells, such as developing neurons, differently than they do adult cells, says Olsen, who coauthored the Neuronpaper describing KORD, the newest DREADD. But in general, Sternson says, “they’re completely complementary methods, and they can in principle be used together in the same animal.”

Another consideration is that PSEMs tend to take slightly longer to work—15 minutes, compared with the DREADD ligand CNO, which takes 5–10 minutes. On the other hand, PSEMs tend to take less time to clear from the body, 1–2 hours (vs. about 2 hours for CNO). Salvinorin B, the ligand of the new KOR-based DREADD, works almost instantaneously, and the effects last less than an hour. Although these differences are minor, they may factor into your experiment.

Experimental procedure

The operational steps are similar for both tools. Most people inject viruses carrying the engineered receptors into the brain area of interest and wait two to three weeks for expression. They then administer the ligand and make their measurements.
If you’ve already performed stereotactically guided brain surgery, there’s nothing new to learn. For newcomers, a Journal of Visualized Experiments protocol describes the surgery and injection of the virally ferried chemogenetic tools (100:e52859, 2015), though it’s best to learn by shadowing someone with experience, Roth says.

Viral constructs for both DREADDs and PSAMs are available from Addgene. For DREADDs, the UNC Vector Core sells high-titer virus stocks. CNO is available for free or at a reduced price for NIH-funded investigators through the National Institute of Drug Abuse’s Drug Supply Program. For PSAMs, you make your own receptor-carrying virus. Sternson provides PSEMs to researchers for their pilot experiments, and they are available for purchase through Apex Scientific for about $15 for 10 mg, he says.

You don’t necessarily need to do surgery if you can afford mutant mice whose DREADDs are under the control of an inducible promoter, such as Cre. Such mice are available through Jackson Labs. In general, just be sure to use validated Cre driver lines, Roth says.

You should make sure the receptor is expressed and working in vitro before you move to whole animals. Expression of both DREADDs and PSAMs is linked to the translation of a fluorescent protein. On his blog, chemogenetic.blogspot.com, Roth gives more specific advice on immunofluorescent staining for visualization of DREADDs.

To make sure that the receptors are actually working involves more-detailed studies, such as the calcium imaging Olsen used to ascertain whether his activating DREADD responded to the ligand, or electrophysiological studies in slices, but the particulars depend on what mechanism your receptor-ligand uses.

“One thing that’s important to know when using these receptors is that they’re not completely off when expressed at high levels,” Conklin says, referring to DREADDs. “[Simply] by expressing them, one cannot be sure.” To get around potential abnormal background activity, you have to include a control without the receptor. Also, having a good label on the receptor is helpful. Using DREADDs in combination with an inducible transcription system, such as Cre, allows you to measure receptor expression before and after inducing it.

Future uses

Although DREADDs and PSAMs-PSEMs are proving to be useful research tools for cell biologists and neurobiologists, both Roth and Sternson are actively developing orthogonal systems for potential clinical use, either as gene-based therapies that would go directly into humans or to be used in stem cell–based therapies.

 

Chemogenetic tools to interrogate brain functions.

Annu Rev Neurosci. 2014;37:387-407. doi: 10.1146/annurev-neuro-071013-014048. Epub 2014 Jun 16.

Elucidating the roles of neuronal cell types for physiology and behavior is essential for understanding brain functions. Perturbation of neuron electrical activity can be used to probe the causal relationship between neuronal cell types and behavior. New genetically encoded neuron perturbation tools have been developed for remotely controlling neuron function using small molecules that activate engineered receptors that can be targeted to cell types using genetic methods. Here we describe recent progress for approaches using genetically engineered receptors that selectively interact with small molecules. Called “chemogenetics,” receptors with diverse cellular functions have been developed that facilitate the selective pharmacological control over a diverse range of cell-signaling processes, including electrical activity, for molecularly defined cell types. These tools have revealed remarkably specific behavioral physiological influences for molecularly defined cell types that are often intermingled with populations having different or even opposite functions.

 

A Method for Remotely Silencing Neural Activity in Rodents During Discrete Phases of Learning.

J Vis Exp. 2015 Jun 22;(100):e52859. doi: 10.3791/52859.

This protocol describes how to temporarily and remotely silence neuronal activity in discrete brain regions while animals are engaged in learning and memory tasks. The approach combines pharmacogenetics (Designer-Receptors-Exclusively-Activated-by-Designer-Drugs) with a behavioral paradigm (sensory preconditioning) that is designed to distinguish between different forms of learning. Specifically, viral-mediated delivery is used to express a genetically modified inhibitory G-protein coupled receptor (the Designer Receptor) into a discrete brain region in the rodent. Three weeks later, when designer receptor expression levels are high, a pharmacological agent (the Designer Drug) is administered systemically 30 min prior to a specific behavioral session. The drug has affinity for the designer receptor and thus results in inhibition of neurons that express the designer receptor, but is otherwise biologically inert. The brain region remains silenced for 2-5 hr (depending on the dose and route of administration). Upon completion of the behavioral paradigm, brain tissue is assessed for correct placement and receptor expression. This approach is particularly useful for determining the contribution of individual brain regions to specific components of behavior and can be used across any number of behavioral paradigms.
It is important to indicate that after the protein has being made it acts in fast form (milliseconds etc,) as protein do…

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Ablation Techniques in Interventional Oncology

Author and Curator: Dror Nir, PhD

“Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes.”; WikipediA.

The use of ablative techniques in medicine is known for decades. By the late 90s, the ability to manipulate ablation sources and control their application to area of interest improved to a level that triggered their adaptation to cancer treatment. To date, ablation  is still a controversial treatment, yet steadily growing in it’s offerings to very specific cancer patients’ population.

The attractiveness in ablation as a form of cancer treatment is in the promise of minimal invasiveness, focused tissue destruction and better quality of life due to the ability to partially maintain viability of affected organs.  The main challenges preventing wider adaptation of ablative treatments are: the inability to noninvasively assess the level of cancerous tissue destruction during treatment; resulting in metastatic recurrence of the disease and the insufficient isolation of the treatment area from its surrounding.   This frequently results In addition, post-ablation salvage treatments are much more complicated. Since failed ablative treatment represents a lost opportunity to apply effective treatment to the primary tumor the current trend is to apply such treatments to low-grade cancers.

Nevertheless, the attractiveness of treating cancer in a focused way that preserves the long-term quality of life continuously feeds the development efforts and investments related to introduction of new and improved ablative treatments giving the hope that sometime in the future focused ablative treatment will reach its full potential.

The following paper reviews the main ablation techniques that are available for use today: Percutaneous image-guided ablation of bone and soft tissue tumours: a review of available techniques and protective measures.

Abstract

Background

Primary or metastatic osseous and soft tissue lesions can be treated by ablation techniques.

Methods

These techniques are classified into chemical ablation (including ethanol or acetic acid injection) and thermal ablation (including laser, radiofrequency, microwave, cryoablation, radiofrequency ionisation and MR-guided HIFU). Ablation can be performed either alone or in combination with surgical or other percutaneous techniques.

Results

In most cases, ablation provides curative treatment for benign lesions and malignant lesions up to 3 cm. Furthermore, it can be a palliative treatment providing pain reduction and local control of the disease, diminishing the tumor burden and mass effect on organs. Ablation may result in bone weakening; therefore, whenever stabilization is undermined, bone augmentation should follow ablation depending on the lesion size and location.

Conclusion

Thermal ablation of bone and soft tissues demonstrates high success and relatively low complication rates. However, the most common complication is the iatrogenic thermal damage of surrounding sensitive structures. Nervous structures are very sensitive to extremely high and low temperatures with resultant transient or permanent neurological damage. Thermal damage can cause normal bone osteonecrosis in the lesion’s periphery, surrounding muscular atrophy and scarring, and skin burns. Successful thermal ablation requires a sufficient ablation volume and thermal protection of the surrounding vulnerable structures.

Teaching points

Percutaneous ablations constitute a safe and efficacious therapy for treatment of osteoid osteoma.

Ablation techniques can treat painful malignant MSK lesions and provide local tumor control.

Thermal ablation of bone and soft tissues demonstrates high success and low complication rates.

Nerves, cartilage and skin are sensitive to extremely high and low temperatures.

Successful thermal ablation occasionally requires thermal protection of the surrounding structures.

For the purpose of this chapter we picked up three techniques:

Radiofrequency ablation

Straight or expandable percutaneously placed electrodes deliver a high-frequency alternating current, which causes ionic agitation with resultant frictional heat (temperatures of 60–100 ˚C) that produces protein denaturation and coagulation necrosis [8]. Concerning active protective techniques, all kinds of gas dissection can be performed. Hydrodissection is performed with dextrose 5 % (acts as an insulator as opposed to normal saline, which acts as a conductor). All kinds of skin cooling, thermal and neural monitoring can be performed.

 

Microwave ablation

Straight percutaneously placed antennae deliver electromagnetic microwaves (915 or 2,450 MHz) with resultant frictional heat (temperatures of 60–100 ˚C) that produces protein denaturation and coagulation necrosis [8]. Concerning active protective techniques, all kinds of gas dissection can be performed, whilst hydrodissection is usually avoided (MWA is based on agitation of water molecules for energy transmission). All kinds of skin cooling, thermal and neural monitoring can be performed.

Percutaneous ablation of malignant metastatic lesions is performed under imaging guidance, extended local sterility measures and antibiotic prophylaxis. Whenever the ablation zone is expected to extend up to 1 cm close to critical structures (e.g. the nerve root, skin, etc.), all the necessary thermal protection techniques should be applied (Fig. 3).

13244_2014_332_Fig3_HTML

a Painful soft tissue mass infiltrating the left T10 posterior rib. b A microwave antenna is percutaneously inserted inside the mass. Due to the proximity to the skin a sterile glove filled with cold water is placed over the skin. c CT axial scan 3 months

Irreversible Electroporation (IRE)

Each cell membrane point has a local transmembrane voltage that determines a dynamic phenomenon called electroporation (reversible or irreversible) [16]. Electroporation is manifested by specific transmembrane voltage thresholds related to a given pulse duration and shape. Thus, a threshold for an electronic field magnitude is defined and only cells with higher electric field magnitudes than this threshold are electroporated. IRE produces persistent nano-sized membrane pores compromising the viability of cells [16]. On the other hand, collagen and other supporting structures remain unaffected. The IRE generator produces direct current (25–45 A) electric pulses of high voltage (1,500–3,000 V).

Lastly we wish to highlight a method that is mostly used on patients diagnosed at intermediate or advanced clinical stages of Hepatocellular Carcinoma (HCC); transarterial chemoembolization  (TACE)

“Transcatheter arterial chemoembolization (also called transarterial chemoembolization or TACE) is a minimally invasive procedure performed in interventional radiology  to restrict a tumor’s blood supply. Small embolic particles coated with chemotherapeutic agents are injected selectively into an artery directly supplying a tumor. TACE derives its beneficial effect by two primary mechanisms. Most tumors within the liver are supplied by the proper hepatic artery, so arterial embolization preferentially interrupts the tumor’s blood supply and stalls growth until neovascularization. Secondly, focused administration of chemotherapy allows for delivery of a higher dose to the tissue while simultaneously reducing systemic exposure, which is typically the dose limiting factor. This effect is potentiated by the fact that the chemotherapeutic drug is not washed out from the tumor vascular bed by blood flow after embolization. Effectively, this results in a higher concentration of drug to be in contact with the tumor for a longer period of time. Park et al. conceptualized carcinogenesis of HCC as a multistep process involving parenchymal arterialization, sinusoidal capillarization, and development of unpaired arteries (a vital component of tumor angiogenesis). All these events lead to a gradual shift in tumor blood supply from portal to arterial circulation. This concept has been validated using dynamic imaging modalities by various investigators. Sigurdson et al. demonstrated that when an agent was infused via the hepatic artery, intratumoral concentrations were ten times greater compared to when agents were administered through the portal vein. Hence, arterial treatment targets the tumor while normal liver is relatively spared. Embolization induces ischemic necrosis of tumor causing a failure of the transmembrane pump, resulting in a greater absorption of agents by the tumor cells. Tissue concentration of agents within the tumor is greater than 40 times that of the surrounding normal liver.”; WikipediA

A recent open access research paper: Conventional transarterial chemoembolization versus drug-eluting bead transarterial chemoembolization for the treatment of hepatocellular carcinoma is discussing recent clinical approaches  related to this techniques.

Abstract

Background

To compare the overall survival of patients with hepatocellular carcinoma (HCC) who were treated with lipiodol-based conventional transarterial chemoembolization (cTACE) with that of patients treated with drug-eluting bead transarterial chemoembolization (DEB-TACE).

Methods

By an electronic search of our radiology information system, we identified 674 patients that received TACE between November 2002 and July 2013. A total of 520 patients received cTACE, and 154 received DEB-TACE. In total, 424 patients were excluded for the following reasons: tumor type other than HCC (n = 91), liver transplantation after TACE (n = 119), lack of histological grading (n = 58), incomplete laboratory values (n = 15), other reasons (e.g., previous systemic chemotherapy) (n = 114), or were lost to follow-up (n = 27). Therefore, 250 patients were finally included for comparative analysis (n = 174 cTACE; n = 76 DEB-TACE).

Results

There were no significant differences between the two groups regarding sex, overall status (Barcelona Clinic Liver Cancer classification), liver function (Child-Pugh), portal invasion, tumor load, or tumor grading (all p > 0.05). The mean number of treatment sessions was 4 ± 3.1 in the cTACE group versus 2.9 ± 1.8 in the DEB-TACE group (p = 0.01). Median survival was 409 days (95 % CI: 321–488 days) in the cTACE group, compared with 369 days (95 % CI: 310–589 days) in the DEB-TACE group (p = 0.76). In the subgroup of Child A patients, the survival was 602 days (484–792 days) for cTACE versus 627 days (364–788 days) for DEB-TACE (p = 0.39). In Child B/C patients, the survival was considerably lower: 223 days (165–315 days) for cTACE versus 226 days (114–335 days) for DEB-TACE (p = 0.53).

Conclusion

The present study showed no significant difference in overall survival between cTACE and DEB-TACE in patients with HCC. However, the significantly lower number of treatments needed in the DEB-TACE group makes it a more appealing treatment option than cTACE for appropriately selected patients with unresectable HCC.

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