Fundamental Studies On The Effect Of Antisense HIF-1α Gene Therapy In Improving The Radiosensitivity Of Salivary Gland Malignant Tumors

Hypoxia inducible factor-la (HIF-la) is a master regulator of the transcription of many different factors involved in the biological progress of malignant tumors. The purpose of this study was to investigate the expression of HIF-la in malignant salivary gland tumors and to evaluate the in vitro radiobiological response of human mucoepidermoid carcinoma cell line MC-1 and human adenocystic carcinoma cell line ACC-2. Furthermore, we try to investigate the effect of in vitro transfection of antisense HIF-la oligonucleotides under normoxic condition on the sensitivity of the two tumor cell lines.MTT assay was employed to detect the survival fraction of the two malignant salivary gland tumor cell lines after different dose of ¹⁹²Ir high dose rateyray brachytherapy. The survival curves were synthesized according to the MTT results via statistic program, and some of the main radiobiological parameters were determined. The morphological and ultrastructure changes of the two cell lines after brachytherapy were also observed through both optical microscope and transmission electron microscope. Both MC-1 cells and ACC-1 cells showed low radiosensitivity to ¹⁹²Iryray, SF₂ values of which were 0.879 and 0.987 respectively.LsAB immunohistochemistry staining was applied in this study to evaluate the expression levels of HIF-1a and CD34 in malignant salivary gland tumors. The relationship between HIF-1a expression and clinical pathological factorswere analysised. HIF-la high expression were observed in both adenocystic carcinoma and mucoepidermoid carcinoma specimens. There was no significant relationship between HIF-la expression and the clinical stages or pathological differentiation, while high expression of HIF-la was correlated with higher microvessels density.Antisense HIF-laoligonucleotides were transfected into MC-1 and ACC-1 cells. Changes of the radiobiological reaction of the two cell lines via flow cytometry and MTT assay. Antisense HIF-laoligonucleotides transfection under normoxic condition increased the apoptosis rate to the two cell lines significantly, and SF2 values of MC-1 cells and ACC-1 cells were dropped to 0.63 and 0.84 respectively.