Abstract: Objective To investigate the effect of the over- expressed CTCF on apoptosis factors Bax and Bcl- 2 in human breast cancer cell line MDA-MB-231. Methods Reverse transcription-polymerase chain reaction (RT-PCR) were used to detect the expressions of CTCF，Bax and Bcl-2 in MDA-MB-231. The overexpression vector of CTCF/pEGFP-N1 was constructed. The overexpression plasmid CTCF/pEGFP-N1 and the empty vector plasmid pEGFP-N1 were transfected into breast cancer cell line MDA-MB-231 by lentivirus transfection, and the MDA-MB-231 cells were divided into CTCF group and control group. After successfully transfection of MDA-MB-231 identified by RT-PCR, real time quantitative PCR (Q-PCR) was used to detect the mRNA levels of Bax and Bcl-2 in MDA-MB-231 of the CTCF group and the control group. The protein levels of Bax and Bcl-2 were detected by Western blot assay and enzyme-linked immunosorbent assay (ELISA). Results The expression of CTCF was not found in MDA-MB-231, and expressions of Bax and Bcl-2 were found in MDAMB-231. Results of Q-PCR showed that the mRNA levels of Bax were 4.63±1.08 and 2.27±0.16 in CTCF group and control group, respectively, and they were statistically significant (t=27.50, P<0.05). The mRNA levels of Bcl-2 were 1.39±0.14 and 3.56 ± 0.97 in CTCF group and control group, and there was significant difference between two groups(t=39.00, P<0.05). Results of Western blot assay showed that the protein level of Bax was higher in CTCF group compared with that of control group. The protein level of Bcl-2 was lower in CTCF group compared with that of control group. Results of ELISA showed that the protein levels of Bax were 15.25±2.17 and 6.24±1.78 in CTCF group and control group, respectively, and there was significant difference between the two groups (t=26.84, P<0.05). The protein levels of Bcl- 2 were 4.59±0.97 and 10.68± 1.93, and there was significant difference between the two groups (t=21.72, P＜0.05). Conclusion The over- expressed CTCF can promote the expression of apoptotic factors and inhibit the expression of anti-apoptotic factors in breast cancer cells.

Key words: breast neoplasms, bcl-2-associated X protein, genes, bcl-2, CTCF, apoptosis factors