Anti-apoptotic brain and reproductive organ-expressed proteins enhance cisplatin resistance in lung cancer cells via the protein kinase B signaling pathway

SMAD4-induced knockdown of the antisense long noncoding RNA BRE-AS contributes to granulosa cell apoptosis

Antisense long noncoding RNAs (AS-lncRNAs), a sub-class of lncRNAs, are transcribed in the opposite direction from their overlapping protein-coding genes and are implicated in various physiological and pathological processes. However, their role in female reproduction remains largely unknown. Here, we report that BRE-AS, an AS-lncRNA transcript from intron 10 of the protein-coding gene BRE, is involved in granulosa cell (GC) apoptosis. Based on our previous RNA sequencing data, we identified 28 AS-lncRNAs as important in the initiation of porcine follicular atresia, with BRE-AS showing the most significant upregulation in early atretic follicles. In this study, gain- and loss-of-function assays demonstrated that BRE-AS induces early apoptosis in GCs. Mechanistically, BRE-AS acts in cis to suppress the expression of BRE, an anti-apoptotic factor, via direct interaction with the pre-mRNA transcript of the latter, inducing increased GC apoptosis. Notably, we also found that BRE-AS was upregulated in SMAD4-silenced GCs. SMAD4 was identified as a transcriptional repressor of BRE-AS because it inhibits BRE-AS expression and BRE-AS-mediated GC apoptosis. In conclusion, we not only identified a novel AS-lncRNA related to the early apoptosis of GCs and initiation of follicular atresia but also described a novel regulatory pathway, SMAD4/BRE-AS/BRE, coordinating GC function and female fertility.

Role of ARK5 in cancer and other diseases (Review)

Malignant tumors are often exposed to hypoxic and glucose-starved microenvironments. AMP-activated protein kinase (AMPK) is an energy sensor that is stimulated during energy-deficient conditions and protects cells from hypoxic injury by regulating metabolism. AMPK-related protein kinase 5 (ARK5) is a member of the catalytic sub-unit of the AMPK family and has an important role in energy regulation and hypoxia. ARK5 is regulated by Akt and liver kinase B1 and is associated with numerous tumor-related molecules to exert the negative effects of tumors. Studies have revealed ARK5 overexpression in cases of tumor invasion and metastasis and a positive association with the degree of cancer cell malignancy, which is regarded as a key element in determining cancer prognosis. Furthermore, ARK5 downregulation improves drug sensitivity through the epithelial-mesenchymal transition pathway, indicating that it may be a potential therapeutic target. In other non-cancer conditions, ARK5 has various roles in neurodegenerative diseases (Alzheimer's and Huntington's disease), renal disorders (diabetic nephropathy and renal fibrosis) and physiological processes (striated muscle generation). In the present review, the upstream and downstream molecular pathways of ARK5 in cancer and other diseases are described and potential therapeutic strategies are discussed.

Pharmacogenomics in epithelial ovarian cancer first-line treatment outcome: validation of GWAS-associated NRG3 rs1649942 and BRE rs7572644 variants in an independent cohort

The identification of predictive biomarkers for the first-line treatment of epithelial ovarian cancer (EOC) remains a challenge. Although genome-wide association studies (GWAS) have identified several genetic polymorphisms as predictors of EOC clinical outcome, the subsequent validation has not yet been performed. This study aims to validate the influence of Neuregulin 3 (NRG3) rs1649942 and Brain and reproductive organ-expressed (TNFRSF1A modulator) (BRE) rs7572644 GWAS-identified variants in an independent cohort of EOC patients from the North region of Portugal (n = 339) submitted to first-line treatment. Polymorphism genotypes were determined by real-time PCR using validated assays. Patients carrying the NRG3 rs1649942 A allele presented a significantly longer overall survival (OS) when compared to GG-genotype patients (log-rank test, P = 0.011) in the FIGO IV stage subgroup. No impact was observed for early-stage patients or considering disease-free survival (DFS) as an outcome. For FIGO I/II stage patients, BRE rs7572644 C allele carriers exhibit a decreased OS (P = 0.014) and DFS (P = 0.032) when compared to TT-homozygous patients. Furthermore, a Multivariate Cox regression analysis revealed a three-fold increase in the risk of death (HR, 3.09; P = 0.015) and recurrence (HR, 3.33; P = 0.009) for FIGO I/II C allele carriers. No significant impact was observed for late-stage patients. The BRE rs7572644 and NRG3 rs1649942 genetic variants were validated in an independent cohort of EOC Portuguese patients, particularly in specific subgroups considering FIGO staging. Further functional post-GWAS analyses are indispensable to understand the biological mechanisms underlying the observed results.

MicroRNA-137-regulated AKT serine/threonine kinase 2 inhibits tumor growth and sensitizes cisplatin in patients with non-small cell lung cancer

The present study investigated the role of microRNA-137-regulated AKT serine/threonine kinase 2 (AKT2) on tumor growth and cisplatin sensitivity in patients with non-small cell lung cancer (NSCLC). The results demonstrated that the expression of microRNA-137 in cisplatin-treated NSCLC patient tissue samples was markedly lower than that in healthy tissue samples. The disease-free survival and overall survival rates of patients with NSCLC exhibiting a high microRNA-137 expression were higher than the survival rates of patients with NSCLC exhibiting a low expression of microRNA-137. Overexpression of microRNA-137 inhibited the proliferation of A549 and H520 cells treated with cisplatin. Overexpression of miR-137 suppressed the protein expression of AKT2, increased caspase-3 activity, increased Bax protein expression and suppressed Cyclin D1 protein expression in A549 and H520 cells treated with cisplatin. MK2206, an AKT2 inhibitor, inhibited AKT2 protein expression and suppressed the proliferation of A549 and H520 cells treated with cisplatin following overexpression of miR-137. The inhibition of AKT2 also increased caspase-3 activity and Bax protein expression, and suppressed Cyclin D1 protein expression in A549 and H520 cells treated with cisplatin following overexpression of miR-137. Taken together, the results of the present study suggested that microRNA-137-regulated AKT2 inhibits tumor growth and sensitizes cisplatin in patients with NSCLC.

LDR reverses DDP resistance in ovarian cancer cells by affecting ERCC-1, Bcl-2, Survivin and Caspase-3 expressions

BACKGROUND

Ovarian cancer is the most frequent cause of death resulting from malignant gynecological tumors. After surgical intervention, cisplatin (DDP) is a major chemotherapy drug for ovarian cancer, but the ovarian cancer cells tend to develop DDP resistance in the clinical setting. Tumor cells are sensitive to low-dose radiation (LDR). However, how the LDR therapy improves the effects of chemotherapy drugs on ovarian cancer is not well understood. This study aimed to explore this issue.

METHODS

The SKOV3/DDP cells were divided into 3 groups, including low-dose group, conventional-dose group, and control group (no radiation). Cell counting kit-8 assay was performed to measure cell proliferation. Flow cytometric analysis was then utilized to quantify the apoptosis with classical Annexin V/propidium iodide co-staining. And Real-time quantitative PCR and western blot were eventually used to analyze the mRNA and protein levels of excision repair cross complementing-group 1 (ERCC1), B-cell lymphoma 2 (Bcl-2), Survivin and Caspase-3, respectively.

RESULTS

The IC50 value of DDP in the low-dose group was significantly lower compared with the other two groups. Compared with the conventional-dose group and control group, LDR treatment resulted in significantly more apoptosis. Besides, LDR treatment significantly decreased the mRNA and protein expression of ERCC1, Bcl-2, and Survivin, and enhanced the mRNA and protein expression of Caspase-3 compared with the other two groups.

CONCLUSIONS

LDR reversed DDP resistance in SKOV3/DDP cells possibly by suppressing ERCC1, Bcl-2, and Survivin expressions, and increasing Caspase-3 expression.

Long non‑coding RNA AK001796 contributes to cisplatin resistance of non‑small cell lung cancer

Cisplatin (DDP)‑based chemotherapy is the most widely used therapy for non‑small cell lung cancer (NSCLC). However, the existence of chemoresistance has become a major limitation in its efficacy. Long non‑coding RNAs (lncRNAs) have been shown to be involved in chemotherapy drug resistance. The aim of the present study was to investigate the biological role of lncRNA AK001796 in cisplatin‑resistant NSCLC A549/DDP cells. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) analysis was performed to monitor the differences in the expression of AK001796 in cisplatin-resistant (A549/DDP) cells and parental A549 cells. Cellular sensitivity to cisplatin and cell viability were examined using an MTT assay. Cell apoptosis and cell cycle distribution were measured using flow cytometry. The expression levels of cell cycle proteins cyclin C (CCNC), baculoviral IAP repeat containing 5 (BIRC5), cyclin‑dependent kinase 1 (CDK1) and G2 and S phase‑expressed 1 (GTSE1) were assessed using RT‑qPCR and western blot analyses. It was found that the expression of AK001796 was increased in A549/DDP cells, compared with that in A549 cells. The knockdown of AK001796 by small interfering RNA reduced cellular cisplatin resistance and cell viability, and resulted in cell‑cycle arrest, with a marked increase in the proportion of A549/DDP cells in the G0/G1 phase. By contrast, the knockdown of AK001796 increased the number of apoptotic cancer cells during cisplatin treatment. It was also shown that the knockdown of AK001796 positively induced the expression of cell apoptosis‑associated factors, CCNC and BIRC5, and suppressed the expression of cell cycle‑associated factors, CDK1 and GTSE5. Taken together, these findings indicated that lncRNA AK001796 increased the resistance of NSCLC cells to cisplatin through regulating cell apoptosis and cell proliferation, and thus provides an attractive therapeutic target for NSCLC.

Inhibition of AMPK-related kinase 5 (ARK5) enhances cisplatin cytotoxicity in non-small cell lung cancer cells through regulation of epithelial-mesenchymal transition

Lung cancer incidence and mortality rates are amongst the highest of all malignant tumors worldwide. ARK5 is a member of the human AMP-activated protein kinase (AMPK) family which is implicated in tumor survival and progression. The current study was designed to explore the role of ARK5 in resistance of non-small cell lung cancer (NSCLC) to cisplatin. We studied the sensitivity of two NSCLC cell lines, NCI-H1229 and A549, to cisplatin by using proliferation and cell viability assays. We then examined expression of ARK5, Twist, and the epithelial to mesenchymal transition (EMT) biomarkers, E-cadherin and Vimentin, by Western blot and immunofluorescence. We found that ARK5 downregulation significantly increased the cisplatin chemosensitivity of NSCLC cells, and that NCI-H1299 cells, which express high levels of ARK5 and possess a mesenchymal phenotype, were more resistant to cisplatin than A549 cells, which show low expression ARK5. Furthermore, siRNA-mediated silencing of ARK5 resulted in altered EMT patterns in NSCLC cells. These data support a role for ARK5 in regulating EMT in NSCLC cells. Together, our findings suggest that ARK5 is a potential drug target for combating drug resistance and regulating EMT in NSCLC cells.

Familial Lung Cancer: A Brief History from the Earliest Work to the Most Recent Studies

Lung cancer is the deadliest cancer in the United States, killing roughly one of four cancer patients in 2016. While it is well-established that lung cancer is caused primarily by environmental effects (particularly tobacco smoking), there is evidence for genetic susceptibility. Lung cancer has been shown to aggregate in families, and segregation analyses have hypothesized a major susceptibility locus for the disease. Genetic association studies have provided strong evidence for common risk variants of small-to-moderate effect. Rare and highly penetrant alleles have been identified by linkage studies, including on 6q23-25. Though not common, some germline mutations have also been identified via sequencing studies. Ongoing genomics studies aim to identify additional high penetrance germline susceptibility alleles for this deadly disease.