Molecular mechanism of chemoresistance by miR-215 in osteosarcoma and colon cancer cells

作者：Song, Bo; Wang, Yuan; Titmus, Matthew A.; Botchkina, Galina; Formentini, Andrea; Kornmann, Marko; Ju, Jingfang^*

来源：Molecular Cancer, 2010, 9(1): 96.

DOI：10.1186/1476-4598-9-96

• THYMIDYLATE SYNTHASE EXPRESSION
• MATRIX-ASSOCIATED PROTEIN
• TUMOR-SUPPRESSOR NETWORK
• MESSENGER-RNA
• GENE-EXPRESSION
• STEM-CELLS
• REGULATED NUCLEAR
• TRANSLATIONAL REGULATION
• DIHYDROFOLATE-REDUCTASE
• COLORECTAL-CANCER

Background: Translational control mediated by non-coding microRNAs ( miRNAs) plays a key role in the mechanism of cellular resistance to anti-cancer drug treatment. Dihydrofolate reductase ( DHFR) and thymidylate synthase (TYMS, TS) are two of the most important targets for antifolate- and fluoropyrimidine-based chemotherapies in the past 50 years. In this study, we investigated the roles of miR-215 in the chemoresistance to DHFR inhibitor methotrexate (MTX) and TS inhibitor Tomudex (TDX).
Results: The protein levels of both DHFR and TS were suppressed by miR-215 without the alteration of the target mRNA transcript levels. Interestingly, despite the down-regulation of DHFR and TS proteins, ectopic expression of miR-215 resulted in a decreased sensitivity to MTX and TDX. Paradoxically, gene-specific small-interfering RNAs (siRNAs) against DHFR or TS had the opposite effect, increasing sensitivity to MTX and TDX. Further studies revealed that overexpression of miR-215 inhibited cell proliferation and triggered cell cycle arrest at G2 phase, and that this effect was accompanied by a p53-dependent up-regulation of p21. The inhibitory effect on cell proliferation was more pronounced in cell lines containing wild-type p53, but was not seen in cells transfected with siRNAs against DHFR or TS. Moreover, denticleless protein homolog (DTL), a cell cycle-regulated nuclear and centrosome protein, was confirmed to be one of the critical targets of miR-215, and knock-down of DTL by siRNA resulted in enhanced G2-arrest, p53 and p21 induction, and reduced cell proliferation. Additionally, cells subjected to siRNA against DTL exhibited increased chemoresistance to MTX and TDX. Endogenous miR-215 was elevated about 3-fold in CD133+HI/CD44+HI colon cancer stem cells that exhibit slow proliferating rate and chemoresistance compared to control bulk CD133+/CD44+ colon cancer cells.
Conclusions: Taken together, our results indicate that miR-215, through the suppression of DTL expression, induces a decreased cell proliferation by causing G2-arrest, thereby leading to an increase in chemoresistance to MTX and TDX. The findings of this study suggest that miR-215 may play a significant role in the mechanism of tumor chemoresistance and it may have a unique potential as a novel biomarker candidate.

• 出版日期2010-4-30
• 单位武汉大学