Apoptosis, 5-fluorouracil sensitivity and expression of apoptotic proteins in a human ectocervical cell...

Apoptosis has received widespread attention for its essential roles in biology, medicine and cancer. We previously found that normal, human papillomavirus (HPV) 16-immortalized and their transformed endocervical cells were increasingly resistant to apoptosis induced by a cancer therapeutic drug. Here, analogously, another common anticancer drug, 5-fluorouracil, in an ectocervical cell carcinogenesis model induced apoptosis in primary human ectocervical cells (HEC), whereas HPV18-immortalized HEC (HEC-18) and transformed HEC-18 (HEC-18T) were more resistant. Growth in serum/low density lipoprotein (LDL)-containing medium reversed resistance to 5-fluorouracil-induced apoptosis, particularly in HEC-18T. Cell viability results confirmed these findings. Using Western blots to compare protein levels with those of HEC not treated with 5-fluorouracil, the fold changes in HEC-18 and HEC-18T in LDL-free medium were 1.6-6.1-fold lower for pro-apoptotic p53, Bak and Bax. Four anti-apoptotic proteins were altered -2.1 to+14.6-fold for Bcl-2 and BAG-1 isoform p33 and p29. For BAG-1 p50 and p46, HEC-18 were weakly expressed and HEC-18T were moderately higher. Grown in LDL-containing medium, the differences in pro-apoptotic protein levels were mostly reversed. Expression was 1.4-32-fold higher in HEC-18 and HEC-18T of p53, Bax, BAG-1 p29, BAG-1 p33 and total BAG-1. These results showed that HEC carcinogenesis results in resistance to 5-fluorouracil-induced apoptosis, associated with reduced expression during carcinogenesis of pro-apoptotic proteins and increased expression of specific anti-apoptotic proteins.