Carbon dioxide, hypoxia and low pH lead to overexpression of c-myc and HMGB-1 oncogenes in neuroblastoma cells

Abstract

Purpose: It has been reported that CO (2) gas, used to establish a pneumoperitoneum during laparoscopy, affects the behavior of tumor cells. The proto-oncogenes C-MYC and HMGB-1 mediate aggressive behavior of neuroblastomas. We studied whether exposure to CO (2), hypoxia or acidosis affects the expression of C-MYC and HMGB-1 in neuroblastoma cells.

Methods: SH-SY5Y cells were incubated with 100% CO (2), 95% helium/5% CO (2) or pH 6.2 for 2 h. The expression of C-MYC and HMGB-1 was measured by Western blot test immediately, 3 h and 6 h after incubation. Additionally, we measured apoptosis after incubation using fluorometric measurements of caspase 3 and 7 activity.

Results: C-myc (160+/-26%, p=0.007 and 138+/-16% vs. control, p=0.04) and HMGB-1 proteins (140+/-13% and 136+/-11%, both p=0.037) were found to be significantly upregulated 6 h after incubation with CO (2) and helium. There was early upregulation of both oncogenes 3 h after CO (2) incubation (251+/-79%, p=0.04 and 292+/-136, p=0.037). Correspondingly, pH 6.2 led to significant overexpression. Levels of apoptosis were reduced.

Conclusions: Exposures mimicking conditions of CO (2) pneumoperitoneum lead to significant overexpression of C-MYC and HMGB-1 in neuroblastoma cells with decreased apoptosis. These results point to a negative influence and potentially increased malignancy of tumor cells.