Current Cancer Drug Targets - Volume 17, Issue 2, 2017

Pristimerin, a natural triterpenoid isolated form Celastrus and Maytenus spp, has been shown to possess a variety of biological and pharmacological effects. Recently, pristimerin has attracted more attention, especially for its potential anticancer activities. The anticancer activities of pristimerin have been illustrated in various cancer cell lines and animal models. It has been found to inhibit in vitro and in vivo proliferation, survival, angiogenesis and metastasis of tumor cells. These activities have been attributed to its modulation of various molecular targets such as cyclins, apoptosis- related proteins, proteasome activity, reactive oxygen species, as well as NF-ΚB, AKT/mTOR and MAPK/ERK pathways. This mini-review discussed the cellular impact and animal studies of pristimerin treatment, with more attention on the various molecular targets of pristimerin.

Urotensin II and Urotensin-II receptors are important molecular factors that regulate vasoconstriction and all the diseases that are linked to abnormalities in blood pressure regulation (i.e.: hypertension, kidney diseases, cirrhosis etc.). Recently, Urotensin II and its receptor have also been involved in metabolic syndrome, diabetes and schizophrenia. Recent strong findings suggest that Urotensin II and its receptor are involved in the onset and development of different epithelial cancers. Indeed, it was reported that cell growth, motility and invasion in human breast, bladder, prostate, colorectal and glioblastoma cancer cells were regulated by Urotensin II and Urotensin-II receptor axis. This axis also regulated focal adhesion kinase and small Guanosine-5'-triphosphate binding proteins that likely had a role in motility and invasion mediated by Urotensin-II receptor. Additionally, its expression on tumour tissues is variably associated to the prediction of the clinical outcome of the patients and it can be considered an alternative molecular marker to be used as prognostic factor in human cancers. In conclusion, a new weapon in the treatment of human cancers is highlighting a new scenario for the future.

Compared to normal cells, usually cancer cells are under higher oxidative stress. Elevating intracellular levels of reactive oxygen species (ROS) by introducing excessive ROS or inhibiting antioxidant system may enhance selectively of cancer cell killing by ROS-modulating agents through stress sensitization or stress overload. Meanwhile due to the adaptive response, normal cells may be capable of maintaining redox homeostasis under exogenous ROS. Here we review ROS-modulating agents in different mechanisms and classify them into groups by various targets for illustrating more clearly. At last, we discuss their side effects and the potential troubles of developing these agents and argue that might be an effective strategy for further exploring to modulate the unique redox regulatory mechanisms of cancer cells.

With increases in our understanding of the human genome and immune system, the treatment armamentarium for melanoma has benefitted from the development and approval of BRAF inhibitors, MEK inhibitors, immune checkpoint modulators via cytotoxic T-lymphocyte antigen-4 blockade, and PD-1 and PD-L1 inhibitors. These advances, however, have raised questions about combination therapy, the optimal sequential use of these agents, the limited assessment of response using traditional metrics, and the optimal selection of the population to be treated. In this review we summarize recent breakthroughs and then itemize the development of newer agents, potential prognostic and predictive biomarkers, resistance mechanisms, and strategies of combination therapy. We also emphasize the multifaceted attributes of immunotherapy in terms of durable responses and longterm survival that paradoxically necessitate further research into the underlying mechanisms and longer patient follow-up.

The evolution of genomic research enabled the genetic and molecular profiling of breast cancer and revealed the profound complexity and heterogeneity of this disease. Subtypes of breast cancer characterized by mutations and/or amplifications of some proto-oncogenes are associated with an increased rate of recurrence and poor prognosis. They represent a challenge in the clinic with limited arsenal to attack them. Nowadays, metabolic reprogramming is firmly established as a hallmark of cancer. An increased rate of lipid and protein syntheses in cancerous tissues, a direct consequence of alterations in key metabolic enzymes involved in these pathways, is now recognized as an important aspect of the rewired metabolism of neoplastic cells. Over the past several years, accumulating evidence has revealed that mutations or amplifications of some proto-oncogenes are primarily involved in this metabolic dysregulation. It is thus critically important to dissect the molecular mechanisms tumors use to link metabolic reprogramming with upstream altered signaling. In this article, we review the recent findings that support the importance of lipid and protein biosyntheses in breast tumorigenesis, discuss the crosstalk between growth factor signal transduction and key metabolic enzymes involved in these processes, and point out the potentials of developing new strategies and therapeutics to target these key parameters in order to help breast cancer patients by providing new therapeutic opportunities.

Background: The epigenetic combinations of DNA demethylating agents and histone deacetylase (HDAC) inhibitors have demonstrated clinical benefits for non-small cell lung cancer (NSCLC) treatment, however, there are few studies uncovering the underlying molecular mechanism of the combinations. Our previous study showed that DNA demethylating agent Azacitidine (Aza) demethylated CpG sites in paired box gene 5 (pax5) promoter region, but did not induce pax5 mRNA or protein expression. Methods: In this study we used epigenetic combination of Aza and HDAC inhibitor Vorinostat (SAHA) to treat NSCLC cells and to elucidate the underlying molecular mechanism. We treated pax5- silenced NSCLC H460 cells with Aza+SAHA combination at sub-toxic concentration and detected the re-expression of pax5 mNRA and protein. Results: The results showed demethylation of CpG sites in pax5 promoter region by Aza treatment and increased DNA accessibility for protein binding by SAHA treatment. The combination of Aza+SAHA significantly increased p53 protein binding to DNA in pax5 promoter region (p<0.01). More efficient binding of the transcription factor p53 to pax5 promoter region is likely because SAHA increased accessibility of the chromatin conformation and Aza-demethylated DNA was more permissive, allowing transcription factors to bind. Conclusion: Our study not only explained an underlying mechanism, that pax5 re-expression was induced by Aza+SAHA combination in H460 cells via p53, but also demonstrated a pattern showing that the combination of demethylating agent and HDAC inhibitor can re-activate tumor suppressor gene (TSG) which is associated with the enhancement of transcription factors binding to the promoter region of the TSG.

Background: ATP-binding cassette (ABC) transporters, P-glycoprotein (P-gp, ABCB1) and breast cancer resistance protein (BCRP/ABCG2) are major determinants of pharmacokinetic, safety and efficacy profiles of drugs thereby effluxing a broad range of endogenous substances across the plasma membrane. Overexpression of these transporters in various tumors is also implicated in the development of multidrug resistance (MDR) and thus, hampers the success of cancer chemotherapy. Modulators of these efflux transporters in combination with chemotherapeutics could be a promising concept to increase the effective intracellular concentration of anticancer drugs. However, broad and overlapped specificity for substrates and modulators of ABCB1 and ABCG2, merely induce toxicity and unwanted drug-drug interactions and thus, lead to late-stage failure of drugs. Objective: In present investigation, we aim to identify specific 3D structural requirements for selective inhibition of ABCB1 and ABCG2 transport function. Method: GRID Independent Molecular Descriptor (GRIND) models of selective inhibitors of both transporters have been developed, using their most probable binding conformations obtained from molecular docking protocol. Results: Our results demonstrated a dominant role of molecular shape and different H-bonding patterns in drug-ABCB1/ABCG2 selective interactions. Moreover, distinct distances of different pharmacophoric features from steric hot spots of the molecules provided a strong basis of selectivity for both transporters. Additionally, our results suggested the presence of two H-bond donors at a distance of 8.4-8.8 Å in selective modulators of ABCG2. Conclusion: Our findings concluded that molecular shape along with three dimensional pattern of Hbonding in MDR modulators play a critical role in determining the selectivity between the two targets.

Background: Studies have demonstrated that cysteine-rich 61 (CYR61) may be involved in tumor proliferation and invasion. However, the role of CYR61 plays in endocrine therapy response is largely unknown. Patients and Methods: We tested the levels of CYR61 expression of 36 primary breast cancer patients who received neo-adjuvant endocrine therapy for at least 3 months by immunohistochemistry staining before and after administrating letrozole, an oral non-steroidal aromatase inhibitor (AI) for the treatment of hormone-responsive breast cancer. The expression levels of CYR61 and ki67 were compared between pre-treatment and post-treatment samples by using the paired t test. Chi-square test was used to determine the relationship between baseline CYR61 expression and clinical response. Results: In the clinical case series analysis, a positive correlation was observed between baseline CYR61 expression and clinical outcomes (p=0.02). CYR61 expression was significantly increased in the residual tumors after treatment (indicating insensitivity to endocrine therapy) compared with that in the baseline biopsy samples, which was irrespective of the efficacy of primary endocrine treatment. In addition, the ki67 level was significantly decreased after neo-adjuvant endocrine therapy, compared with that in the baseline samples. Conclusion: This study provides evidence that CYR61 may confer the sensitivity to letrozole treatment and may offer an opportunity to target CYR61 to improve endocrine resistance in ER-positive breast cancer.