Current Cancer Drug Targets - Volume 18, Issue 9, 2018

Background: Protein kinase B (PKB/Akt) belongs to the AGC superfamily of related serine/ threonine kinases with three structurally homologous mammalian isoforms, Akt1 (PKBα), Akt2 (PKBβ), and Akt3 (PKBγ). Besides sharing a similar structural topology, the difference in their physiological functions and tissue distribution makes Akt a cardinal node in diverse signaling pathways involving cell growth, survival, and proliferation. Various immunohistochemical studies have reported that the constitutive hyperactivation of Akt signaling is responsible for several types of human cancer, poor prognosis, as well as chemotherapeutic and radiotherapeutic resistance. Thus, inhibition of Akt activation represents a promising concept to induce cell apoptosis in various cancers and evade chemotherapeutic resistance. However, development of potent and selective inhibitors of Akt kinases as suitable antagonists remained gloomy and thus, only handful of compounds were selected for the clinical investigation but none of them could reach the market for routine clinical usage to circumvent cell proliferation and resistance to chemotherapeutic agents in cancer. Recent reports on achieving isoform selectivity by designing inhibitors against PH domain of Akt, together with availability of crystal structures of the PH domain of Akt1, open the possibility of structurebased design. Methods: In this article, various biological regulatory networks by which Akt and its substrates regulate cell growth and survival and several SAR and QSAR strategies in combination with molecular docking studies on selective inhibitors of Akt subtypes have been highlighted to further probe the selectivity of ligand-Akt subtypes interactions. Results: Structure-based drug design studies revealed that the interactions of structurally diverse compounds with Glu121, Ala123, Asn171, Asp184, Glu228 and Ala230 amino acid residues in CAT domain and Arg23, Arg25, Lys30, Asn54 and Arg86 amino acid residues within PH domain play an important role in attaining significant inhibitory potency. Conclusion: Isoform selective inhibition of Akt might have clinical significance and thus, should be taken into account in future investigations. Moreover, an up to date isoform selective chemical data is required to further validate already reported isoform selective binding hypothesis.

Ponatinib is a third generation kinase inhibitor designed to overcome the gatekeeper T315I mutation. In different trials this drug showed inhibitory activity against native BCR-ABL1 kinase and several ABL1 mutations. For this reason, ponatinib is currently indicated for the treatment of chronic myeloid leukaemia (CML) in every phase of disease resistant and/or intolerant to dasatinib and nilotinib and for whom imatinib is not indicated anymore or for patients with T315I mutation. The drug is also indicated for Ph+ acute lymphoblastic leukaemia (ALL). Ponatinib was temporarily suspended in 2013 for the occurrence of cardiovascular thrombotic events. Since then, different investigators analyzed baseline characteristics of patient candidates for ponatinib, especially cardiovascular profile, in order to describe general management recommendations in this setting. In this review, clinical trials data about the use of ponatinib in CML and Ph+ ALL patients will be discussed. It will be focused also about the safety and tolerability profile of the drug and future perspectives of employment.

Todays, after four decades from the discovery of monoclonal antibodies by Kohler and Milstein in 1975, a dozen of antibodies are used in cancer targeted therapy with different strategies. The success of these antibodies depends on the specificity of antigens expressed on the cancer cells. Epithelial Cell Adhesion Molecule (EpCAM), a homophilic cell-cell adhesion glycoprotein is a well- known tumor antigen, which expresses on epithelial tumors and circulating tumor cells as well as cancer stem cells. The EpCAM signaling pathway is associated with proliferation, differentiation and adhesion of epithelial cancer cells. Here we review EpCAM structure, expression profile and its signaling pathway in cancer cells. In addition, we focused on structure, mechanism of action and success of anti EpCAM antibodies which have been used in different clinical trials. Based on literatures, Edrecolomab showed limited efficacy in the phase III studies. The wholly human monoclonal antibody Adecatumumab is dose- and target-dependent in metastatic breast cancer patients expressing EpCAM. The chimeric antibody, Catumaxomab, has been approved for the treatment of malignant ascites; however, this Mab showed considerable results in intrapleural administration in cancer patients. Anti EpCAM toxin conjugated antibodies like, Oportuzumab Monatox (scFv antibody and Pseudomonas exotoxin A (ETA)), Citatuzumab Bogatox (Fab fragment with bouganin toxin) and immono-conjugate antibody Tucotuzumab (monoclonal antibody with IL2), have shown acceptable results in different clinical trials. Almost, all of the antibodies were well-tolerated; however, still more clinical trials are needed for the approval of antibodies for the treatment of specific tumors.

Background: Adaptive upregulation of Androgen Receptor (AR) is the most common event involved in the progression from hormone sensitive to Castration-Resistant Prostate Cancer (CRPC). AR signaling remains the main target of new AR signalling-directed therapies such as abiraterone and enzalutamide in CRPC patients. Objective: In this review, we discuss general mechanisms of resistance to AR-targeted therapies, with a focus on the role of AR Copy Number (CN). We reported methods and clinical applications of AR CN evaluation in tissue and liquid biopsy, thus to have a complete information regarding its role as predictive and prognostic biomarker. Conclusion: Outcomes of CRPC patients are reported to be highly variable as the consequence of tumor heterogeneity. AR CN could contribute to patient selection and tumor monitoring in CRPC treated with new anti-cancer treatment as abiraterone and enzalutamide. Further studies to investigate AR CN effect to these agents and its potential combination with other prognostic or predictive clinical factors are necessary in the context of harmonized clinical trial design.

The standard of treatment for advanced ovarian cancer is represented by optimal surgical debulking preceded or followed by chemotherapeutic regimens including taxanes and platinum agents, possibly associated with bevacizumab and/or intraperitoneal therapy. Despite this comprehensive treatment strategy, almost 75% of patients relapse or progress and are therefore candidates for a second-line treatment, showing, at this point, less chemo-sensitivity and worse prognosis. An interesting approach to improve outcomes of these patients has been developed in the last decade, in BRCA-related ovarian cancer. Mutations in one of the BRCA genes result in impaired homologousrecombination DNA repair, which causes genetic abnormalities that promote carcinogenesis. Interestingly, this defect has been exploited by the introduction of poly (ADP-ribose) polymerase (PARP) inhibitors to provide specific cancer cell cytotoxicity. Particularly, the inhibition of PARP in BRCAmutation carriers leads to the persistence of DNA damage usually repaired by the homologousrecombination system, resulting in cell cycle arrest and thus apoptosis. Despite the mechanism of action, an activity of PARP inhibitors was also observed in “BRCAness” ovarian tumors, and in BRCA-related tumors other than ovarian, suggesting that these agents may be active regardless of BRCA mutation status or site of origin. This review aims to describe the principal evidence that led to the development and the study of PARP inhibitors and to discuss their main implications in our daily clinical practice.

Background: Our previous studies revealed that the downregulation of Suppressor of cytokine signaling 6 (SOCS6) was correlated with malignant progression of human prostate cancer (PCa). Aims: In the current study, we aimed to investigate the tumor suppressive roles of SOCS6 and the underlying mechanisms in PCa. Methods: SOCS6 expression in PCa and non-cancerous prostate tissues was compared by immunohistochemistry. Statistical associations of SOCS6 expression with various clinicopathological features and patients prognosis were evaluated. In addition, we investigated SOCS6's functions by overexpressing it in vitro (cell apoptosis, migration and invasion assays) and in vivo (tumor formation, angiogenesis and apoptosis). Moreover, SOCS6-regulated genes were identified by nextgeneration RNA-sequencing analysis, followed by pathway enrichment analysis and in vitro experimental validation. Results: SOCS6 downregulation was significantly associated with advanced clinical stage (P=0.029) and positive lymph node metastasis (P=0.013) in PCa patients. We also identified SOCS6 as an independent prognostic factor for disease-free survival in PCa patients (P=0.045). Moreover, overexpression of SOCS6 inhibited PCa cell invasion, migration, tumor xenografts growth and angiogenesis, but induced PCa cell apoptosis (P values <0.05). Mechanically, we revealed that SOCS6 expression may induce cell apoptosis coincident with down-regulation of Bcl2 and Hspa1a, and may suppress tumor angiogenesis with downregulation of F7, Fak3 and Frzb. Conclusion: These findings suggest that the reduced expression of SOCS6 may be predictive of unfavorable prognosis in PCa. Thus, SOCS6 may serve as a tumor suppressor and a novel therapeutic target for this cancer.

Background: Recent epidemiological and experimental studies have shown that obesity is a major risk factor for Colorectal Cancer (CRC). Regular intake of high fat-containing diet can promote obesity and metabolic syndrome by increasing the insulin resistance and inflammatory response which contribute to carcinogenesis. Previously, we have shown that inhibition of polyol pathway enzyme aldose reductase (AR) prevents carcinogens- and inflammatory growth factorsinduced CRC. However, the effect of AR inhibition on a high-fat diet (HFD)-induced formation of intestinal polyps in Apc-deficient Min (multiple intestinal neoplasia; ApcMin/+) mice is not known. Methods: We examined the effect of AR inhibitor, fidarestat on the HFD-induced formation of preneoplastic intestinal polyps in ApcMin/+ mice which is an excellent model of colon cancer. Results: APCMin/+ mice fed for 12 weeks of HFD caused a significant increase in the formation of polyps in the small and large intestines and fidarestat given along with the HFD prevented the number of intestinal polyps. Fidarestat also decreased the size of the polyps in the intestines of HFDtreated APC Min mice. Further, the expression levels of beta-catenin, PCNA, PKC-β2, P-AKT, Pp65, COX-2, and iNOS in the small and large intestines of HFD-treated mice significantly increased, and AR inhibitor prevented it. Conclusion: Our results thus suggest that fidarestat could be used as a potential chemopreventive drug for intestinal cancers due to APC gene mutations.