circRNAs in drug resistance of breast cancer.

Breast cancer (BC) is the most common heterogeneous disease in women and one of the leading causes of cancer-related death. Surgery, chemotherapy, radiotherapy, hormone, and targeted therapy are the gold standards for BC treatment. One of the significant challenges during the treatment of BC represents resistance to chemotherapeutics, resistance that severely limits the use and effectiveness of the drugs used for BC treatment. Therefore, it is essential to develop new strategies to improve therapeutic efficacy. Circular RNAs (circRNAs) are a large group of non-coding RNAs that covalently form closed circular loops by joining their 5', and 3'; ends. Accumulating evidence suggests that circRNAs have a vital role in cancer development, progression, and BC resistance to chemotherapy. The purpose of this review is to discuss the biological properties of circRNAs, and how circRNAs induce resistance to conventional therapeutic anti-cancer drugs used in BC treatment, by emphasizing and summarizing the potential roles of circRNAs in mechanisms of drug resistance, such as drug efflux, apoptosis dysfunction, autophagy, and DNA damage repair. CircRNAs are associated with drug resistance via ATP-binding cassette (ABC) efflux transporters, while some others by inhibition of cell apoptosis, thus leading to resistance to tamoxifen in BC cells. In contrast, others are involved in the promotion of BC cells chemoresistance by doxorubicin-induced autophagy. CircRNAs may have clinical significance in regulating or overcoming BC drug resistance and may give directions towards a novel approach to personalized BC treatment. CircRNAs may significantly contribute to the identification of new therapeutic targets for the prevention of BC chemoresistance.

Caffeic acid phenethyl ester induces apoptosis in colorectal cancer cells via inhibition of survivin.

Colorectal cancer is one of the most common types of cancer. Drug resistance and drug-induced damage of healthy tissues are major obstacles in cancer treatment. Therefore, to develop efficient anticancer therapy, it is necessary to find compounds that affect tumor cells, but do not exhibit toxicity to healthy cells. Caffeic acid phenethyl ester (CAPE) has been demonstrated to have anticancer properties in many types of cancer. In this study, the cytotoxic and apoptotic effects of CAPE on the RKO colorectal cancer cell line and CCD 841-CoN normal colorectal cell line was investigated. In addition, changes in the survivin expression were determined. According to the results, CAPE decreased cell viability in the RKO cell line in a dose-dependent manner. Likewise, CAPE induced apoptotic cell death in approximately 40% of the RKO cells. Furthermore, CAPE treatment increased the Serine 15 (Ser15) and Serine 46 (Ser46) phosphorylation of p53, while decreased the survivin expression. The results suggested that CAPE induced apoptosis by regulating p53 phosphorylation, leading to inhibition of the survivin expression. In accordance with the results, it is suggested that CAPE might be evaluated as an alternative drug in cancer therapy and further investigation is needed within this scope.

Associations between cytokine gene polymorphisms and rheumatoid arthritis in Turkish population.

OBJECTIVE: Various cytokine polymorphisms have been associated with genetic risk factors predisposing to Rheumatoid Arthritis (RA) in different populations. To predict the clinical outcome as well as response to therapy in RA, studies aimed to describe genetic markers. The present study aims to search for polymorphisms of 13 cytokine coding genes in the Eastern Black Sea Region of Turkey. METHODS: DNAs of 49 patients and 96 healthy bone marrow and kidney donors were isolated from peripheral blood samples. Genotyping was performed using the Heidelberg Cytokine Typing Tray kit. PCR products were visualized on an agarose gel, and results were analyzed using the interpretation scheme provided with the kit. Arlequin 3.5 software was used for statistical analysis. RESULTS: No positive association was found between allele frequencies and the disease. However, a negative association was found for the IL-A -889 C allele (p=0.02, OR=0.533, Wald's 95% CI=0.318-0.893). IL-12 -1188 CC (p=0.01, OR=3.667, Wald's 95% CI=1.246-10.786), IL-4 -1098 GT (p=0.02, OR=2.405, Wald's 95% CI=1.129-5.125) genotypes were found positively associated with the RA, while IL-4 -590 CT (p=0.02, OR=0.422, Wald's 95% CI=0.201-0.886) was found negatively associated with the disease. In addition, IL-6 GG haplotype was found positively associated with the RA (p=0.02, OR=1.880, Wald's 95% CI=1.086-3.254). CONCLUSION: Our findings suggest that some polymorphisms of the IL-1A, IL-2, IL-4, IL-6 and IL-12 could be responsible for the susceptibility or protective to RA in our study population. Multi-centered and large numbers of subjects containing studies that search for cytokine polymorphisms will gather more information regarding the susceptibility to RA of Turkish patients.

Keratin 14 is a novel interaction partner of keratinocyte differentiation regulator: receptor-interacting protein kinase 4.

The epidermis, the outer layer of the skin, is formed by stratified keratinocyte layers. The self-renewal of the epidermis is provided by sustained proliferation and differentiation of the keratinocyte stem cells localized to the basal layer of the epidermis. Receptor-interacting protein kinase 4 (RIPK4) is an important regulator of keratinocyte differentiation, mutations of which are associated with congenital ectodermal malformations. In an attempt to identify the molecular basis of RIPK4's function, we applied yeast two-hybrid screen (Y2H) and found basal layer-specific keratin filament component keratin 14 (KRT14) as a novel RIPK4-interacting partner. During keratinocyte differentiation, layer-specific keratin composition is tightly regulated. Likewise, the basal layer specific KRT14/keratin 5 (KRT5) heterodimers are replaced by keratin 1 (KRT1)/keratin 10 (KRT10) in suprabasal layers. The regulation of keratin turnover is under the control of signaling associated with posttranslational modifications in which phosphorylation plays a major role. In this study, we verified the KRT14-RIPK4 interaction, which was identified with Y2H, in mammalian cells and showed that the interaction was direct by using proteins expressed in bacteria. According to our results, the N-terminal kinase domain of RIPK4 is responsible for KRT14-RIPK4 interaction; however, the RIPK4 kinase activity is dispensable for the interaction. In accordance with their interaction, RIPK4 and KRT14 colocalize within the cells, particularly at keratin filaments associated with perinuclear ring-like structures. Moreover, RIPK4 did not show any effect on KRT14/KRT5 heterodimer formation. Our results suggest that RIPK4 may regulate the keratin turnover required for keratinocyte differentiation through interacting with KRT14.