RESUMO
<p><b>OBJECTIVE</b>To investigate the expression and gene mutation of cluster of differentiation 9 (CD9) in the pathway of the mineral powder induced malignant transformation in immortalized human bronchial epithelial cells (BEAS-2B) in Gejiu.</p><p><b>METHODS</b>BEAS-2B cells served as the control group and its malignant transformation cells induced by mineral powder in Gejiu were considered as experiment group. The expression of CD9 protein in 20 bottles of BEAS-2B cells and 20 bottles of malignant transformation cells was evaluated by immunocytochemistry. The mRNA expression of CD9 in 10 bottles of BEAS-2B cells and 10 bottles of malignant transformation cells was examined by reverse transcriptase polymerase chain reaction (RT-PCR). Gene mutation was detected in the products of RT-PCR by DNA sequencing.</p><p><b>RESULTS</b>There was significant difference between the expression of CD9 protein in BEAS-2B cells (100%, 20/20) and that in its malignant transformation cells (35%, 7/20 P < 0.01). The expression of CD9 mRNA in BEAS-2B cells 0.91 +/- 0.09 was significantly higher than that in its malignant transformation cells (0.34 +/- 0.14) (P < 0.01). Two point mutation of CD9 gene was detected in the malignant transformation cells of BEAS-2B by DNA sequencing. The change of G-->T in the base of 231 led to the change of Gln-->His in the amino acids of 40. The change of T-->A in the base of 119 led to the change of Val-->Asp in the amino acids of 3.</p><p><b>CONCLUSION</b>The absence or down-regulation of CD9 expression and point mutation in the malignant transformation cells of BEAS-2B may play a considerable role in the pathway of the malignant transformation in the BEAS-2B cells induced by mineral powder in Gejiu.</p>