[Inhibitory effect of bladder cancer related protein gene on HeLa cell proliferation]

Bladder cancer related protein (BLCAP) gene was found downregulated most in primary cervical cancer tissues using oncogene/tumor suppressor gene microarray screening in our previous study, therefore this study was to explore the possible correlation between BLCAP gene and cervical cancer.

BLCAP expression was investigated in 54 cervical cancer and 25 normal tissues by reverse transcription polymerase chain reaction (RT-PCR). Full length of BLCAP cDNA was cloned into pLXSN expression vector and stably transfected into cervical cancer cell line HeLa cells. Cell proliferation, colony formation ability and apoptosis were determined by cell number counting, colony formation and DNA ladder assay. Nude mice were used to study the anti-tumor effect of BLCAP gene in vivo.

BLCAP gene expression was significantly down-regulated or even not observed in human cervical cancer tissues compared to the normal ones. The cell doubling time of HeLa cells transfected with BLCAP was significantly elevated to 69.4 hrs (P<0.05), compared to that of the parental cells (27.5 hrs) or cells transfected with empty vectors (30.2 hrs). Moreover, in comparison with control cells, the colony formation efficiency of cells transfected with BLCAP gene was significantly lower (t=5.98, P<0.01). BLCAP expression also sensitized Hela cells to apoptosis induced by serum deprivation. In vivo, smaller size of tumors were formed in mice after the injection of cells transfected with BLCAP for 30 days compared to those injected with parental cells or cells transfected with empty vector (tumor wet weights were 1.015 g, 1.612 g, and 1.530 g, respectively, P<0.05). Furthermore, under pathological examinations, tumor tissues formed by cells transfected with BLCAP gene displayed less invasive potential with integral vascular fibrous capsules; muscle or adipocyte tissue invasion was not observed. In comparison, necropsy revealed that the tumors formed from the control cells were attached to the underlying muscles; histologically, the neoplastic cells were locally invasive and associated with fibrous connective tissues. These cells exhibited severer cytoplasmic and nuclear pleomorphism compared to cells transfected with BLCAP.

BLCAP gene is down-regulated in cervical carcinoma tissues and could suppress tumorigenic ability and growth of HeLa cells, thus it may be a potential suppressor candidate gene of cervical carcinoma.