[The expression of c-myc in the tissues of human laryngeal squamous cell carcinoma and the effect of siRNA-mediated inhibition of c-myc on proliferation in laryngeal carcinoma Hep-2 cells].
OBJECTIVE
To detect the expression of c-myc in the tissue of laryngeal squamous cell carcinoma. RNA interference(RNAi) was employed to inhibit the expression of c-myc in Hep-2 cells and to evaluate the effects of c-myc as a target for gene therapy in laryngeal carcinoma.


METHODS
Immunohistochemistry was used to determine the protein levels of c-myc and Rb in 80 cases of laryngeal squamous cell carcinoma and 30 cases of polyp of vocal cord. Hep-2 cells were transfected with c-myc siRNA, c-myc protein and mRNA levels were detected using Western Blotting and RT-PCR. Cell viability was detected by MTT after the Hep-2 cells were transfected with c-myc siRNA for different times or transfected with different concentrations c-myc siRNA. The sensitivity of Hep-2 cells to 5-Fu transfected with or without c-myc siRNA was evaluated also by MTT. Hep-2 cells were transfected with c-myc siRNA in combination with 5-Fu for 48 h and then analyzed cell apoptosis by flow cytometry.


RESULTS
Immunohistochemical analysis showed that c-myc was highly expressed in the tissues of laryngeal squamous cell carcinoma while the expression of Rb was lower. The protein and mRNA levels of c-myc decreased after transfected with c-myc siRNA. The results of MTT showed that the c-myc siRNA inhibited Hep-2 cells growth in a concentration-dependent manner. When transfected with c-myc siRNA(50 nmol/L), the cells were inhibited in a time-dependent manner. Compared with the untransfected cells, the viability of transfected Hep-2 cells was significantly suppressed at the same concentration of 5-Fu (P < 0.05). C-myc siRNA combination with 5-Fu could obviously increase cell apoptosis, even in the low concentration of 5-Fu (P < 0.05).


CONCLUSIONS
The protein level of C-myc has highly expressed in tumor tissues. C-myc siRNA can effectively inhibit the expression of c-myc and has anti-proliferation effects, increasing the sensitivity of Hep-2 cells to 5-Fu. Therefore,c-myc might be a good target for cancer treatment.
Department of Otorhinolaryngology Head and Neck Surgery, the First Affiliated Hospital, Zhengzhou University, Zhengzhou, 450052, China.
Jianzhong
J
Sang
Li
L
Liu
Fang
F
Tian
Hongjun
H
Jin
Linlin
L
Yuan
Weihua
W
Lou
D000328:Adult; D000368:Aged; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D007822:Laryngeal Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics
D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D034741:RNA, Small Interfering