Novel Mechanisms of Resistance to Novel Agents
Curators: Larry H. Berstein, M.D. FACP & Stephen J. Williams, Ph.D.
For most of the history of chemotherapy drug development, predicting the possible mechanisms of drug resistance that ensued could be surmised from the drug’s pharmacologic mechanism of action. In other words, a tumor would develop resistance merely by altering the pathways/systems which the drug relied on for mechanism of action. For example, as elucidated in later chapters in this book, most cytotoxic chemotherapies like cisplatin and cyclophosphamide were developed to bind DNA and disrupt the cycling cell, thereby resulting in cell cycle arrest and eventually cell death or resulting in such a degree of genotoxicity which would result in great amount of DNA fragmentation. These DNA-damaging agents efficacy was shown to be reliant on their ability to form DNA adducts and lesions. Therefore increasing DNA repair could result in a tumor cell becoming resistant to these drugs. In addition, if drug concentration was merely decreased in these cells, by an enhanced drug efflux as seen with the ABC transporters, then there would be less drug available for these DNA adducts to be generated. A plethora of literature has been generated on this particular topic.
However in the era of chemotherapies developed against targets only expressed in tumor cells (such as Gleevec against the Bcr-Abl fusion protein in chronic myeloid leukemia), this paradigm had changed as clinical cases of resistance had rapidly developed soon after the advent of these compounds and new paradigms of resistance mechanisms were discovered.
Although there are many other new mechanisms of resistance to personalized medicine agents (which are discussed later in the chapter) this post is a curation of cellular changes which are not commonly discussed in reviews of chemoresistance and separated in three main categories:
Cellular Diversity and Adaptation
Expression of microRNAs and alterations in RNA resulting in chemo-resistance
Overexpression of miR-200c induces chemoresistance in esophageal cancers mediated through activation of the Akt signaling pathway
Gene Duplication of Therapeutic Target
The advent of Gleevec (imatinib) had issued in a new era of chemotherapy, a personalized medicine approach by determining the and a lifesaver to chronic myeloid leukemia (CML) patients whose tumors displayed expression of the Bcr-Abl fusion gene. However it was not long before clinical resistance was seen to this therapy and, it was shown amplification of the drug target can lead to tumor outgrowth despite adequate drug exposure. le Coutre, Weisberg and Mahon23, 24, 25 all independently generated imatinib-resistant clones through serial passage of the cells in imatinib-containing media and demonstrated elevated Abl kinase activity due to a genetic amplification of the Bcr–Abl sequence. However, all of these samples were derived in vitro and may not represent a true mode of clinical resistance. Nevertheless, Gorre et al.26 obtained specimens, directly patients demonstrating imatinib resistance, and using fluorescence in situ hybridization analysis, genetic duplication of the Bcr–Abl gene was identified as one possible source of the resistance. Additional sporadic examples of amplification of the Bcr–Abl sequence have been clinically described, but the majority of patients presenting with either primary or secondary imatinib resistance fail to clinically demonstrate Abl amplification as a primary mode of treatment failure.
This is seen in the following papers:
Clinical resistance to STI-571 cancer therapy caused by BCR-ABL gene mutation or amplification.Gorre ME, Mohammed M, Ellwood K, Hsu N, Paquette R, Rao PN, Sawyers CL. Science. 2001 Aug 3;293(5531):876-80. Epub 2001 Jun 21.
and in another original paper by le Coutre et. al.
Induction of resistance to the Abelson inhibitor STI571 in human leukemic cells through gene amplification. le Coutre P1, Tassi E, Varella-Garcia M, Barni R, Mologni L, Cabrita G, Marchesi E, Supino R, Gambacorti-Passerini C. Blood. 2000 Mar 1;95(5):1758-66
The 2-phenylaminopyrimidine derivative STI571 has been shown to selectively inhibit the tyrosine kinase domain of the oncogenic bcr/abl fusion protein. The activity of this inhibitor has been demonstrated so far both in vitro with bcr/abl expressing cells derived from leukemic patients, and in vivo on nude mice inoculated with bcr/abl positive cells. Yet, no information is available on whether leukemic cells can develop resistance to bcr/abl inhibition. The human bcr/abl expressing cell line LAMA84 was cultured with increasing concentrations of STI571. After approximately 6 months of culture, a new cell line was obtained and named LAMA84R. This newly selected cell line showed an IC50 for the STI571 (1.0 microM) 10-fold higher than the IC50 (0.1 microM) of the parental sensitive cell line. Treatment with STI571 was shown to increase both the early and late apoptotic fraction in LAMA84 but not in LAMA84R. The induction of apoptosis in LAMA84 was associated with the activation of caspase 3-like activity, which did not develop in the resistant LAMA84R cell line. LAMA84R cells showed increased levels of bcr/abl protein and mRNA when compared to LAMA84 cells. FISH analysis with BCR- and ABL-specific probes in LAMA84R cells revealed the presence of a marker chromosome containing approximately 13 to 14 copies of the BCR/ABL gene. Thus, overexpression of the Bcr/Abl protein mediated through gene amplification is associated with and probably determines resistance of human leukemic cells to STI571 in vitro. (Blood. 2000;95:1758-1766)
This is actually the opposite case with other personalized therapies like the EGFR inhibitor gefinitib where actually the AMPLIFICATION of the therapeutic target EGFR is correlated with better response to drug in
Molecular mechanisms of epidermal growth factor receptor (EGFR) activation and response to gefitinib and other EGFR-targeting drugs.Ono M, Kuwano M. Clin Cancer Res. 2006 Dec 15;12(24):7242-51. Review.
The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases, including EGFR, HER2/erbB2, and HER3/erbB3, is an attractive target for antitumor strategies. Aberrant EGFR signaling is correlated with progression of various malignancies, and somatic tyrosine kinase domain mutations in the EGFR gene have been discovered in patients with non-small cell lung cancer responding to EGFR-targeting small molecular agents, such as gefitinib and erlotinib. EGFR overexpression is thought to be the principal mechanism of activation in various malignant tumors. Moreover, an increased EGFR copy number is associated with improved survival in non-small cell lung cancer patients, suggesting that increased expression of mutant and/or wild-type EGFR molecules could be molecular determinants of responses to gefitinib. However, as EGFR mutations and/or gene gains are not observed in all patients who respond partially to treatment, alternative mechanisms might confer sensitivity to EGFR-targeting agents. Preclinical studies showed that sensitivity to EGFR tyrosine kinase inhibitors depends on how closely cell survival and growth signalings are coupled with EGFR, and also with HER2 and HER3, in each cancer. This review also describes a possible association between EGFR phosphorylation and drug sensitivity in cancer cells, as well as discussing the antiangiogenic effect of gefitinib in association with EGFR activation and phosphatidylinositol 3-kinase/Akt activation in vascular endothelial cells.
Mutant Variants of Therapeutic Target
Mutational Landscape of Rare Childhood Brain Cancer: Analysis of 60 Intercranial Germ Cell Tumor Cases using NGS, SNP and Expression Array Analysis – Signaling Pathways KIT/RAS are affected by mutations in IGCTs
AND seen with the ALK inhibitors as well (as seen in the following papers
Hashida S, Yamamoto H, Shien K, Miyoshi Y, Ohtsuka T, Suzawa K, Watanabe M, Maki Y, Soh J, Asano H, Tsukuda K, Miyoshi S, Toyooka S. Cancer Sci. 2015 Oct;106(10):1377-84. doi: 10.1111/cas.12749. Epub 2015 Sep 30.
Nanjo S, Nakagawa T, Takeuchi S, Kita K, Fukuda K, Nakada M, Uehara H, Nishihara H, Hara E, Uramoto H, Tanaka F, Yano S. Cancer Sci. 2015 Mar;106(3):244-52. doi: 10.1111/cas.12600. Epub 2015 Feb 17.
Identification of a novel HIP1-ALK fusion variant in Non-Small-Cell Lung Cancer (NSCLC) and discovery of ALK I1171 (I1171N/S) mutations in two ALK-rearranged NSCLC patients with resistance to Alectinib. Ou SH, Klempner SJ, Greenbowe JR, Azada M, Schrock AB, Ali SM, Ross JS, Stephens PJ, Miller VA.J Thorac Oncol. 2014 Dec;9(12):1821-5
Reports of chemoresistance due to variants have also been seen with the BRAF inhibitors like vemurafenib and dabrafenib:
Watson IR, Li L, Cabeceiras PK, Mahdavi M, Gutschner T, Genovese G, Wang G, Fang Z, Tepper JM, Stemke-Hale K, Tsai KY, Davies MA, Mills GB, Chin L.Cancer Res. 2014 Sep 1;74(17):4845-52. doi: 10.1158/0008-5472.CAN-14-1232-T. Epub 2014 Jul 23