Resistance to chemotherapeutics abrogates the efficacy of current cancer therapies and presents an additional layer of adversities to anticancer drug development. Several commonly prescribed anti-cancer drugs have some form of resistance related challenges. Therefore, studying the underlying mechanisms of drug resistance in cancer cells will increase our understanding and reveal important information that can be used to overcome resistance and improve cancer therapy. We examined the resistance mechanisms of M2, a drug candidate targeting the MCM complex. A resistant cell model (R10) was generated through exposure to gradually increasing doses of M2 (up to 500 ng/ml). Upon characterization, R10 showed 6.3-fold more resistance to M2 compared to the sensitive counterpart. Additionally, R10...[ Read more ]

Resistance to chemotherapeutics abrogates the efficacy of current cancer therapies and presents an additional layer of adversities to anticancer drug development. Several commonly prescribed anti-cancer drugs have some form of resistance related challenges. Therefore, studying the underlying mechanisms of drug resistance in cancer cells will increase our understanding and reveal important information that can be used to overcome resistance and improve cancer therapy. We examined the resistance mechanisms of M2, a drug candidate targeting the MCM complex. A resistant cell model (R10) was generated through exposure to gradually increasing doses of M2 (up to 500 ng/ml). Upon characterization, R10 showed 6.3-fold more resistance to M2 compared to the sensitive counterpart. Additionally, R10 exhibited many intrinsic phenotypic characteristics such as enhanced antiapoptotic potential, increased doubling time, slow cell cycle progression and variation in the level of chromatin bound MCM. Furthermore, the heterogenous and dynamic nature of resistant cancer population (R10) led us to study the resistance mechanisms in single-cell clones (SCCs), to dissect the complex heterogeneity of resistance. We isolated SCCs from R10. The detailed analysis of 6 clones revealed broadly different drug resistance mechanisms. We found that three clones showed specific resistance (SR1-3) only to M2 while the other three clones displayed multidrug resistance (MR1-3). Our results demonstrated that MR clones exhibit reduced drug uptake potential in comparison to the parental cell line. Moreover, the upregulation of mesenchymal markers, MCM2, -5 & -7p is consistent with the aggressive nature and metastatic potential of the SR and MR clones. In a chemically confined microenvironment, multi-daughter cell formation was observed in different cancer cell lines. In addition to this, we studied the role of NOC3p in Eukaryotic ORC Dimerization and DNA Replication. Our co-IP results showed that ORC dimerization is NOC3p dependent in budding yeast and human cells. Furthermore, the confirmation of these novel processes of protein dimerization in human cells through cryo-EM will help to screen for anticancer agents targeting these proteins in cancer cells. Taken together, our data provide evidence of heterogeneity within the M2-resistant cancer cell population, including an increase in MCM expression, a reduction in drug uptake, EMT acquisition and multipolar mitosis in a chemically altered environment. These findings highlight the ability of resistant cancer cells to evolve sub clonal populations and necessitates clonal based treatment strategies to overcome resistance.