Abstract 2577: Blocking Janus activated kinase-2 activation by DIM suppresses ovarian tumor growth in vitro and in vivo

Abstract

Abstract Ovarian cancer is one of the leading causes of gynecological deaths in the United States and several other countries. Genetic alterations including overexpression of EGFR and STAT-3 play a crucial role in the signal transduction pathways that regulate key cellular functions such as cell survival, proliferation, metastases etc. Several epidemiological studies suggested a decreased risk of ovarian cancer in the population consuming Brassica vegetables. 3,3′-diindolylmethane (DIM) is an indole compound present in Brassica vegetables. In our previous studies, we have demonstrated that DIM induces apoptosis in ovarian cancer cells by inhibiting the activation STAT-3. However, the exact mechanism of STAT-3 regulation by DIM was not clear. Accumulating evidences suggest that Janus Activated Kinases (JAK's) play a crucial role in regulating STAT-3. Our current results show that DIM inhibits the activation of JAK-2 by blocking its phosphorylation at Tyr-1007/1008 in a concentration-dependent manner in SKOV-3 and OVCAR-3 cells. Inhibition of JAK-2 phosphorylation by DIM was as early as one hour after DIM treatment. The expression of survivin was significantly reduced by DIM. IL-3 is a cytokine that specifically activates JAK-2. Treatment of SKOV-3 or OVCAR-3 cells with 10ng/ml IL-3 for 15min not only increased the activation of JAK-2 and STAT-3, but also induced the expression of STAT-3. DIM treatment almost completely blocked IL-3 induced phosphorylation of JAK-2 and STAT-3 in SKOV-3 and OVCAR-3 cells. Several studies have shown that JAK's are regulated by EGFR, hence to test this, cells were stimulated with EGF, a specific ligand of EGFR. As expected, EGF treatment increased the activation of JAK-2 and STAT-3 in SKOV-3 cells. Nonetheless, DIM treatment blocked the phosphorylation of JAK-2 and STAT-3 induced by EGF. Furthermore, our in vivo studies demonstrated that oral administration of 3 mg DIM for 40 days significantly suppressed the growth of ovarian tumors xenografts in athymic nude mice. The tumors of DIM treated mice exhibited reduced phosphorylation of JAK-2, EGFR and STAT-3 and increased apoptosis. These results indicate that DIM induces apoptosis in ovarian tumor cells by regulating JAK-2 activation in vitro and in vivo. [Supported in part by R01 grants CA 106953 and CA 129038 awarded to S.K.S by National Cancer Institute, NIH] Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2577. doi:1538-7445.AM2012-2577