Abstract 1802: Genomic changes elicited by mitomycin C that confer increased sensitivity of peritoneal cancer cells to death ligands

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Mitomycin C (MMC) can be administered by hyperthermic intraperitoneal chemotherapy (HIPEC) for the treatment of advanced peritoneal cancers (PC) following de-bulking surgery. This strategy produces superior tumor control compared to surgery alone. Nevertheless, most patients relapse within 2 years justifying the need for additional treatment modalities. We have investigated the effects of MMC on the expression of genes that control tumor sensitivity to apoptosis and antitumor immunity and the consequences on in vitro proliferation of PC cells in the presence of different immunologic death ligands. PC cells included the T84 ATCC established cell line, as well as single cell suspensions from surgical specimens of patients with metastatic colon cancer involving the ovary, the stomach and 1 patient with peritoneal carcinomatosis of unknown origin. Tumor genomic expression was assessed by real time PCR and tumor proliferation by the MTS assay. MMC treatment produced a dose-dependent inhibition of proliferation of the T84 cell line ranging from -0.1% (5ng/mL) through 76.5% (250ng/mL). Dose dependent inhibition of proliferation was also observed with cells from human colon cancer specimens with inhibition ranging from 0.3% (5ng/mL) to as much as 83.6% (250ng/mL). A sublethal, pharmacologically-achievable concentration of MMC (25ng/mL) consistently caused significantly increased (2.5-7.5 fold compared to media) expression of various pro-apoptotic genes including: Bax; BIK; DAP Kinase 1; GADD45A; as well as increased (3.3-6.3 fold) expression of caspase-related genes including: CARD6 and caspases 1, 8 and 10. MMC treated cells were also found consistently to express significantly increased (2.3-7.7 fold) levels of FAS and TNF-related death receptors. Notably, the same concentration of MMC either inhibited or did not change the expression of anti-apoptotic genes and did not change expression of potential inhibitors of immunologic lysis such as FAS ligand. These genomic results suggested that there could be additive inhibitory effects of MMC with selected death ligands on the proliferation of PC cells. In fact, the combination of MMC + rTNF inhibited proliferation by 67% compared with 28% and 44% for MMC and rTNF alone respectively. Similar results were obtained with the combination of MMC + rTRAIL (PC cell inhibition = 83% for MMC + rTRAIL vs 28% and 61% for MMC and rTRAIL alone respectively). This study demonstrates that MMC, a standard HIPEC agent employed for the control of residual intraperitoneal tumor following de-bulking surgery, elicits genomic and functional changes that render human PC cells more sensitive to the inhibitory effects of the death ligands, TNF and TRAIL. The results provide a rationale for treatment modalities that stimulate antitumor immunity and the production of immunologic death ligands in the peritoneal cavity of PC patients following HIPEC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1802. doi:10.1158/1538-7445.AM2011-1802