Current Cancer Drug Targets - Volume 17, Issue 7, 2017

Background: Involvement of mutations in epigenetic mechanism in the development of heterogeneous MDS and its evolution to AML has been understood with at least one mutation and median of 2-3 mutations of the landscapes of driver mutations in ~40 genes described in >90% MDS patients. Exclusivity and cooperating effects of mutations have directed therapeutic implementation with hypomethylating agents and identified a number of first-in-class small molecules as inhibitors of mutational expression. Preclinical and clinical trials have already been initiated for some synthetic and natural products and established proof-of-concept for mitigation of mutagenic effects. Objective: The present review article entails the mutational signatures in DNA-methylation and hydroxymethylation, histone acetylation and Deacetylation, polycomb repressor complex (PRC2), and small molecule inhibitors of these mutational expressions. Method: Information has been collected from the recently published literature available mainly through Google search in Medline and PubMed database. Special emphasis was paid on the literature available during 2009-2016. Result: The up-to-date information accumulated on signature-mutations and their inhibitors has to integrate the function of clonal hematopoiesis of indeterminate potential (CHIP) and mutational complexities for re-defining MDS-genesis. Nevertheless, molecular understanding of MDS heterogeneity and its transformation to AML is expanding at fast pace with expanding knowledge on abundant non-coding RNAs (ncRNAs), which forms the basis of targeted drug-tailoring, and will further develop personalized medicines based on individual genetic blue-prints. Conclusion: Mutation-specific targeted epigenetic drugs, which have already sensitized drug-makers and regulators, may promise attestation of ‘del5q and lenalidomide’-like specific drugs for every mutational signature independently or in combination with standard therapeutic elements used for MDS-management, and that will add to understand their antagonistic/synergistic effects.

Background: Aldo-keto reductase 1C3 (AKR1C3) is an important oxidoreductase with multiple substrates, that are involved in producing extra-testicular androgens. Its activity is influenced by environmental exposures, as well as by genetic variants. These genetic variants could therefore produce variable testosterone levels and subsequent androgen receptor (AR) activation. This could lead to differential downstream production of the prostate-specific antigen (PSA). As PSA level is used for clinical evaluation of the prostate, these variations could impact prostate cancer (PC) diagnosis, as well as PC management outcomes. This review brings together information with regards to key functions of this enzyme, its relevance in PC, its transcriptional regulation, clinical aspects associated with genetics, differential regulation in cancer and cancer progression, and the types of AKR1C3 inhibitors with future therapeutic value. Conclusion: Based on these discussions, hypotheses are forwarded for future applicability of this enzyme and its genetic variants in transformational medical practices in PC. Options for the use of personalised AKR1C3 inhibitor drugs for late stage PC are also discussed.

Background: Epidermal growth factor receptor (EGFR) is a well-recognised drug target exploited for treating non-small cell lung cancer (NSCLC). Gefitinib and erlotinib are first generation clinically employed inhibitors used against EGFR activating mutants. However, during course of treatment these inhibitors become ineffective due to the emergence of an acquired secondary mutation. Subsequently, in order to overcome non-responsiveness second and third generation inhibitors were designed having covalent bond and irreversible mode of action. However, these inhibitors were shown to be toxic. This led to the discovery of lead candidates with completely different mode of action and therapeutic efficacy. Objective: We have reviewed the recent efforts undertaken by researchers in discovering newer noncovalent reversible next generation inhibitors for treating NSCLC. Methods: We first studied the optimization steps and pharmacokinetic variables of the synthesised molecules. We also analysed bonds and interactions using PDB X-ray crystal structures as well as scaffold and selectivity analysis was undertaken. Results: We identified that ligand lipophilic efficiency driven potency is a preferable optimisation parameter for maintaining drug likeliness of the molecule. Also, few h-bonds were recognised as major players in affecting the binding of compound. The scaffold analysis revealed that ligand molecules with pyrimidine core exhibit higher inhibitory activity against TMLR, as well as higher selectivity with respect to other kinases. Conclusion: Next generation reversible inhibitors exhibited unique binding mode and were found to occupy three major pockets (ribose pocket, back pocket and hinge region), which is critical for increasing the selectivity of the compound against TMLR mutants.

Background: Cyclin-dependent kinase (CDK) 4/6 inhibitor-based therapies have shown great promise in improving clinical outcomes for patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer. Objectives: 1. Discuss the mode of action of the three CDK4/6 inhibitors in late clinical development: palbociclib (PD-0332991; Pfizer), ribociclib (LEE011; Novartis), and abemaciclib (LY2835219; Lilly). 2. Describe the efficacy and safety data relating to their use in HR+, HER2-advanced breast cancer. 3. Discuss the key side effects associated with CDK4/6 inhibitors along with considerations for adverse event management and patient monitoring. Method: Relevant information and data were assimilated from manuscripts, congress publications, and online sources. Results: CDK4/6 inhibitors have demonstrated improved progression-free survival in combination with endocrine therapy compared with endocrine therapy alone. The side-effect profile of each agent is described, along with implications for patient monitoring, and considerations for patient care providers and pharmacists. Conclusion: Addition of a CDK4/6 inhibitor to endocrine therapy increases efficacy and delays disease progression. Insight into the unique side-effect profiles of this class of agents and effective patient monitoring will facilitate the successful use of CDK4/6 inhibitor-based therapies in the clinic.

Background: Osteosarcoma is the most frequent malignant bone tumor in childhood and young adulthood. Long-term survivors of osteosarcoma patients show high prevalence of osteoporosis and fractures. The immunomodulatory mifamurtide, which modulates macrophages activity, improves disease outcome. Objective: To evaluate the role of mifamurtide on macrophage component of bone, the osteoclasts, during chemotherapy in children with osteosarcoma. Method: Osteoclasts, obtained from peripheral blood cells of healthy donors were harvested in the presence or not of mifamurtide. Moreover, osteoclast cultures were obtained from osteosarcoma patients, at onset and during chemotherapy, alone or with mifamurtide. Pro-osteoporotic tartrateresistant acid phosphatase (TRAP), phosphokinase-β-2 (PKCβ2), vanilloid receptor type 1 (TRPV1), and anti-osteoporotic cannabinoid receptor type 2 (CB2) biomarkers were analyzed by bio-molecular (qPCR), biochemical (Western Blotting), and morphological (TRAP assay) approaches. Results: Osteoclasts from osteosarcoma patients show significant increase of TRAP and decrease of CB2 with respect to osteoclasts from healthy donors. This osteoclast hyperactivity is more evident in osteoclasts from osteosarcoma patients during chemotherapy. Mifamurtide reduces pro-osteoporotic TRAP, PKCβ2, TRPV1 levels and increases CB2 in osteoclasts from healthy donors. Moreover, chemotherapy-induced effects on bone resorption markers are fully reverted in osteoclasts derived from osteosarcoma patients in chemotherapy plus mifamurtide. Conclusion: Our data suggest a new therapeutic role for mifamurtide as possible anti-resorption agent in chemotherapy-induced osteoporosis in children with osteosarcoma.

Background: DNA topoisomerase II-α (Top2-α), an essential enzyme for the management of DNA during replication, transcription, recombination, and chromatin remodeling, is one of the most important anticancer targets. Numerous molecules have been designed as Top2-α inhibitors. However, several studies have shown that polymorphisms and mutations in Top2 have conferred resistance to most of these anticancer drugs. The aim of this study was to computationally examine the mechanisms by which genomic variations in Top2-α could affect its resistance to Amsacrine and Mitoxantrone as important inhibitors of the enzyme. Results: The results showed that variants K529E, R568H, R568G and T530M could affect Top2-α inhibition by Amsacrine causing possible drug-resistant. Moreover, R487K, and Y481C variants could change the response of the enzyme to Mitoxantrone. Conclusion: These results could facilitate the prediction and development of more effective drugs for Top2-α variants, making the cancer chemotherapy more effectiv

Background: Resveratrol has been shown to have antioxidant and anti-proliferative properties in multiple cancer types. Here we demonstrate that H460 lung cancer cells are more susceptible to resveratrol treatment in comparison to human bronchial epithelial Beas-2B cells. Resveratrol decreases cell viability and proliferation, and induces significant apoptosis in H460 cells. The apoptosis observed was accompanied by an increase in hydrogen peroxide (H2O2) production, Bid, PARP and caspase 8 activation, and downregulation of pEGFR, pAkt, c-FLIP and NFkB protein expression. Furthermore, treatment with (H2O2) scavenger catalase significantly inhibited resveratrol-induced c-FLIP downregulation, caspase-8 activation and apoptosis. Overexpression of c-FLIP in H460 cells (FLIP cells) resulted in the inhibition of resveratrol-induced (H2O2) production, and a significant increase in resveratrolinduced apoptosis in comparison to H460 cells. In FLIP cells, catalase treatment did not rescue cells from a decrease in cell viability and apoptosis induction by resveratrol as compared to H460 cells. Resveratrol treatment also led to VEGF downregulation in FLIP cells. Furthermore, inhibition of pEGFR or pAkt using erlotinib and LY294002 respectively, enhanced the negative effect of resveratrol on FLIP cell viability and apoptosis. The reverse was observed when FLIP cells were supplemented with EGF, or transfected with WT-AKT plasmid; resulting in a 20% decrease in resveratrol-induced apoptosis. In addition, transfection with WT-AKT plasmid resulted in the inhibition of pro-apoptotic protein activation, and c-FLIP and pAkt downregulation. Conclusion: Overall, resveratrol induced apoptosis in H460 lung cancer cells by specifically targeting pAkt and c-FLIP dowregulation by proteasomal degradation in a EGFR-dependent manner.