Abstract 87: SULF2 methylation is a prognostic biomarker for lung cancer survival and increases sensitivity to camptothecin analogues via expression of ISG15

Abstract

Abstract Heparan sulfate proteoglycans (HSPGs) serve as co-receptors for numerous signaling molecules including growth factors and cytokines. The sulfation pattern on the heparan sulfate (HS) motif is central to the interaction between HSPGs and the myriads of molecules including interferon (INF). SULF2 encodes for HS 6-O-endosulfatase enzyme that removes the 6-O-sulfate moieties from HS and regulates the specificity of this interaction. Increased expression of SULF2 promotes angiogenic and oncogenic signaling. In hepatocellular carcinoma higher expression of SULF2 is associated with worse prognosis after resection. Conversely, we recently reported that methylation-mediated SULF2 silencing is associated better survival of resected lung cancer patients. Here we show that SULF2 methylation is also a favorable survival marker in unresectable lung cancer. Furthermore, epigenetic silencing of SULF2 suppresses cell migration and induces the expression of multiple INF-inducible genes. Knocking down 80% of SULF2 expression in Calu-3 cells using siRNA resulted in 7-fold increase in the expression of INF-inducible regulator of ubiquitination, ISG15. Similarly, lung cancer cell lines with methylated SULF2 (SULF2M) on average express 60-fold higher ISG15 than cell lines with unmethylated SULF2 (SULF2U). ISG15 is a key marker for increased sensitivity of cancer cells to topoisomerase-1 inhibitors such as camptothecin and topotecan. In vitro treatment of lung cancer cell lines with camptothecin revealed a 65-fold higher sensitivity in cell lines with SULF2M and ISG15 high (ISG15H) phenotype compared to SULF2U and ISG15 low (ISG15L) cell lines. In nude mice, 10mg/kg/week topotecan treatment dramatically arrested the growth of SULF2M and ISG15H lung cancer xenografts but had no effect on SULF2U and ISG15L xenografts. Heterogeneity for ISG15 expression was also seen in primary tumors. One third of primary lung tumors have ISG15H phenotype with an average of 5-fold higher expression than the remaining 2/3rd tumors in which the ISG15 level is comparable to normal lung. Taken together these results indicate SULF2 methylation is not only a favorable prognostic marker for lung cancer, but through its association with increased expression of ISG15 could indicate a higher sensitivity to topoisomerase-1 inhibitors. 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 87. doi:10.1158/1538-7445.AM2011-87