Multidrug resistance is the major cause of chemotherapy failure in many solid tumors, including colon cancer. Hypoxic environment is a feature for all solid tumors and is important for the development of tumor resistance to chemotherapy. Hypoxia-inducible factor (HIF)-1α is the key transcription factor that mediates cellular response to hypoxia. HIF-1α has been shown to play an important role in tumor resistance; however, the mechanism is still not fully understood. Here, we found that HIF-1α and the drug resistance-associated gene multidrug resistance associated protein 1 (MRP1) were induced by treatment of colon cancer cells with the hypoxia-mimetic agent cobalt chloride. Inhibition of HIF-1α by RNA interference and dominant-negative protein can significantly reduce the induction of MRP1 by hypoxia. Bioinformatics analysis showed that a hypoxia response element is located at −378 to −373 bp upstream of the transcription start site of MRP1 gene. Luciferase reporter assay combined with mutation analysis confirmed that this element is essential for hypoxia-mediated activation of MRP gene. Furthermore, RNA interference revealed that HIF-1α is necessary for this hypoxia-driven activation of MRP1 promoter. Importantly, chromatin immunoprecipitation analysis demonstrated that HIF-1α could directly bind to this HRE site in vivo. Together, these data suggest that MRP1 is a downstream target gene of HIF-1α, which provides a potential novel mechanism for HIF-1α-mediated drug resistance in colon cancer and maybe other solid tumors as well.

Backgrounds/Aims: MicroRNAs (MiRNAs) control many biological events and play critical roles in the development of tumor. Among all miRNAs, miR203 has been recently shown to have an inhibitory effect on prostate cancer. However, its involvement in the carcinogenesis of breast cancer has not been reported. Methods: We examined the levels of miR203 in the breast cancer from the patients compared to the paired normal breast tissue. We also examined the levels of miR203 in several commonly used breast cancer cell lines. The effects of overexpression or depletion of miR203 on breast cancer cell growth were analyzed by a MTT assay, and on breast cancer cell invasion were examined by a scratch wound healing assay and a transwell cell migration assay. MiR203-targeted genes were analyzed by Western blot. Results: We detected significantly lower levels of miR203 in the breast cancer from the patients compared to the paired normal breast tissue. Moreover, the levels of miR203 were significantly lower in breast cancer tissue from the patients with cancer metastasis. Decreased miR203 levels were detected in all examined breast cancer lines. Overexpression of miR203 inhibited breast cancer cell growth and invasion, while antisense-mediated inhibition of miR203 enhanced cancer cell growth and invasion. Further analyses show that miR203 may inhibit cell growth through decreasing cell-cycle activator cyclinD2 and CDK6, increasing cell-cycle suppressor p21 and p27, and increasing apoptosis-associated protein Bcl-2. MiR203 may also inhibit cell metastasis through suppressing matrix metalloproteinase 2 (MMP2), MMP7 and MMP9. Conclusion: Our data thus highlight miR203 as a novel therapeutic target for breast cancer.

DNA methylation has been reported to become a potential powerful tool for cancer detection and diagnosis. However, the possibilities for the application of blood-based gene methylation as a biomarker for non-small cell lung cancer (NSCLC) detection and screening remain unclear. Hence, we performed this meta-analysis to evaluate the value of gene methylation detected in blood samples as a noninvasive biomarker in NSCLC. A total of 28 genes were analyzed from 37 case-control studies. In the genes with more than three studies, we found that the methylation of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT was significantly associated with risks of NSCLC. The methylation statuses of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT were not linked to age, gender, smoking behavior, and tumor stage and histology in NSCLC. Therefore, the use of the methylation status of P16, RASSF1A, APC, RARβ, DAPK, CDH13, and MGMT could become a promising and powerful biomarker for the detection and screening of NSCLC in blood in clinical settings. Further large-scale studies with large sample sizes are necessary to confirm our findings in the future.

Previous studies report aberrant activation of the hedgehog signaling pathway in the progression of various cancers. This study aimed to investigate the expressions of smoothened and downstream glioma-associated oncogene homology-1 in gastric cancer and the underlying molecular mechanisms. Here, we first detected the expression in 58 cases of primary gastric cancer tissue and matched normal tissue specimens by western blot analysis and quantitative reverse transcription polymerase chain reaction. Cell proliferation and cycle were assayed in gastric cancer cells after blocking the hedgehog pathway by lentiviral-short hairpin RNA knockdown. In vitro inhibition of hedgehog pathway resulted in decreased cell proliferation and migration. Our studies demonstrate an important role for smoothened and glioma-associated oncogene homology-1 in gastric cancer and suggest inhibition of hedgehog pathway as a novel and potent strategy to treat gastric cancer patients.

Background Increasing evidence has shown that circular RNAs (circRNAs) serve as vital regulators in tumour progression. In this study, we focused on the functions of circ_0027599 in gastric cancer (GC) progression. Methods The levels of circ_0027599, runt‐related transcription factor 1 (RUNX1) mRNA and microRNA‐21‐5p (miR‐21‐5p) were detected by quantitative real‐time polymerase chain reaction (qRT‐PCR) assay. The protein levels of RUNX1, E‐Cadherin, vimentin and N‐Cadherin were measured by Western blot assay. Cell viability, colony formation, metastasis and cell cycle process were evaluated by Cell Counting Kit‐8 (CCK‐8) assay, colony formation assay, transwell assay and flow cytometry analysis, respectively. The interaction between circ_0027599 and miR‐21‐5p and the interaction between miR‐21‐5p and RUNX1 were verified by dual‐luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The role of circ_0027599 in tumour growth in vivo was investigated by murine xenograft model assay. Results Circ_0027599 and RUNX1 were downregulated in GC tissues and cells. Circ_0027599 level was associated with the overall survival of GC patients. Circ_0027599 or RUNX1 overexpression inhibited GC cell viability, colony formation, migration, invasion and cell cycle process in vitro. For mechanism analysis, circ_0027599 positively regulated RUNX1 expression via functioning as the sponge for miR‐21‐5p. RUNX1 inhibition reversed circ_0027599 overexpression mediated malignant behaviours of GC cells. Moreover, circ_0027599 overexpression repressed tumour growth in vivo. Conclusion Circ_0027599 overexpression repressed GC progression via modulation of miR‐21‐5p/RUNX1 axis, which might illumine a novel therapeutic target for GC.