BACKGROUND: Radio-resistance is an obstacle to the treatment of human nasopharyngeal carcinoma (NPC). However, how microRNAs (miRNA) are involved in this process remains unclear. In the present study we explored the role and possible molecular mechanism of miR-29a-3p, formerly known as tumor suppressors, in radio-sensitivity of NPC cells.

MATERIAL AND METHODS: A radio-resistant sub-cell line, CNE-2R, was established to detect the expression of miR-29a/b/c-3p using qRT-PCR. CCK-8 assay, colony formation assay, and single-cell gel electrophoresis (SCGE) assay were carried out to analyze the radio-sensitivity of NPC cells. qRT-PCR, luciferase reporter, and Western blot experiments were performed to validate the targeting of COL1A1 by miR-29a. Short interference RNAs (siRNAs) were used to investigate whether COL1A1 mediates the radio-sensitizer role of miR-29a. Expression of miR-29a and COL1A1 in radio-resistant NPC tissues was finally determined.

RESULTS: miR-29a was decreased in the radio-resistant CNE-2R cells. Following a time-course irradiation (IR) exposure, miR-29a exhibited a time-dependent decrease. Cellular experiments confirmed that miR-29a induced radio-sensitivity of CNE-2R cells via suppressing cell viability and enhancing cell apoptosis after IR. We confirmed that COL1A1 is a direct target of miR-29a and can exert radio-resistance effects in NPC cells. We also found that knockdown of COL1A1 inhibits NPC cell viability and sensitivity to IR. Finally, we observed a downregulation of miR-29a in radio-resistant NPC tissues and its decrease was associated with upregulation of COL1A1.

CONCLUSIONS: miR-29a is a critical determinant of NPC radio-response for NPC patients, and its induction provides a promising therapeutic choice to elevate NPC radio-sensitivity.

Keywords: Nasopharyngeal Neoplasms, Radiotherapy, Adjuvant, Collagen Type I, Collagen Type I, alpha 1 Chain, nasopharyngeal carcinoma, Radiation Tolerance, Transfection