Downregulation of miR-3934-5p enhances A549 cell sensitivity to cisplatin by targeting TP53INP1

Tumor protein p53-inducible nuclear protein 1 (TP53INP1) is a tumor suppressor associated with malignant tumor metastasis. In addition, it has been reported that hsa-microRNA (miR)-3934 serves key roles in various types of lung cancer, including small-cell lung carcinomas (SCLC) and non-SCLC (NSCLC). Therefore, the present study aimed to determine the effects of miR-3934-5p on cell proliferation and apoptosis, and on sensitivity to cisplatin (DDP). Reverse transcription-quantitative polymerase chain reaction analysis and western blotting were conducted for the analysis of mRNA and protein expression, respectively. Furthermore, the target of miR-3934-5p was investigated using a luciferase reporter assay and apoptosis was analyzed by flow cytometry. The results demonstrated that miR-3934-5p was upregulated in NSCLC tissues and A549 cells. Increases in the half-maximal inhibitory concentration (IC₅₀) and the expression of miR-3934-5p were observed in the A549/DDP group. miR-3934-5p mimic promoted the expression of miR-3934-5p and the IC₅₀ of the A549 cells. miR-3934-5p inhibitor downregulated miR-3934-5p and reduced the IC₅₀ of A549/DDP cells. miR-3934-5p was revealed to target the 3'-untranslated region of TP53INP1. The downregulation of miR-3934-5p significantly suppressed the proliferation and promoted the apoptosis of A549/DDP cells, which were reversed by transfection with TP53INP1 small interfering (si)RNA. The protein and mRNA expression levels of TP53INP1, B-cell lymphoma 2 (Bcl-2)-associated-X and p21 were significantly increased, whereas those of Bcl-2 were significantly decreased in the miR-3934-5p inhibitor group, which was significantly reduced by TP53INP1 siRNA transfection. miR-3934-5p, as a tumor suppressor in NSCLC, may promote the sensitivity of cells to DDP by targeting TP53INP1, associated with the suppression of cell proliferation and promotion of apoptosis.

Upregulation of let-7f-5p promotes chemotherapeutic resistance in colorectal cancer by directly repressing several pro-apoptotic proteins

Colorectal cancer (CRC) is one of the most frequently occurring primary malignant tumors worldwide. Chemotherapeutic resistance is a major clinical problem in the treatment of CRC. Therefore, it is of great importance to investigate novel biomarkers that may predict chemoresistance and facilitate the development of individualized treatment for patients with CRC. The present study reported that let-7f-5p expression was elevated in chemotherapy-resistant CRC tissues compared with chemotherapy-sensitive tissues. Furthermore, upregulating let-7f-5p increased the expression levels of the anti-apoptotic proteins, B-cell lymphoma 2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xL), and decreased the activity of caspase-3 and caspase-9 in CRC cells. By contrast, downregulating let-7f-5p yielded the opposite effect. Notably, the results indicated that let-7f-5p promoted chemotherapeutic resistance by directly repressing the expression of several pro-apoptotic proteins, including tumor protein p53, tumor protein p53-inducible nuclear protein 1, tumor protein p53-inducible nuclear protein 2 and caspase-3. Therefore, a novel mechanism by which let-7f-5p enhances the resistance of CRC cells to chemotherapeutics has been revealed, indicating that silencing let-7f-5p may become an effective therapeutic strategy against CRC.

MicroRNA‑205 promotes the tumorigenesis of nasopharyngeal carcinoma through targeting tumor protein p53-inducible nuclear protein 1

Nasopharyngeal carcinoma (NPC) is a common type of cancer in southern China, miRNAs have been shown to be involved in the tumorigenesis of multiple cancer types. The present study aimed to explore the potential role of miR‑205 in NPC. Reverse transcription quantitative polymerase chain reaction was used to determine the expression levels of miR‑205 in 20 fresh NPC specimens and 20 normal nasopharyngeal tissues. The function of miR‑205 in the proliferation, migration, invasion and apoptosis of NPC‑derived cells was detected by MTT assay, colony formation assay, wound healing assay, Transwell assay and flow cytometry. Furthermore, a target gene of miR‑205 was identified using the luciferase reporter assay. The expression of miR‑205 was increased in NPC tissues compared with that in normal tissues. Overexpression of miR‑205 was found to promote the proliferation, migration and invasion of NPC‑derived cells, while apoptosis was suppressed. Tumor protein p53-inducible nuclear protein 1 was identified as a target gene of miR‑205. Overall, the present study demonstrated that miR‑205 may function as an oncogene in NPC tumorigenesis.