Uveal melanoma (UM) is the most frequent intraocular tumor in adult patients. When metastases occur, systemic therapy with alkylating agents (fotemustine or dacarbazine (DTIC)) has shown only modest efficacy. The common chemotherapeutic drug doxorubicin (DOX) is not used to treat metastatic UM (mUM). To expand the chemotherapeutic arsenal for mUM, we tested the effect of DOX on UM cell mortality. We have previously shown that CREB knockdown enhances sensitivity to DOX. UM cells infected with recombinant MuLV-based replicative competent retroviruses (RCR) expressing shRNA targeting CREB were co-treated with either DTIC or DOX. We found that CREB knockdown increases the sensitivity of these cells to both DOX and DTIC in normoxia and more so in hypoxia as measured by cell survival and Caspase 3 activation. The ability to combine CREB knockdown by infection with the RCR recombinant virus which preferentially infects replicating tumor cells and chemotherapy to achieve the same amount of cell death in lower concentrations may result in fewer side effects of the drugs. This combination is a possible new treatment for mUM.

Uveal melanoma (UM) is the most prevalent primary intraocular cancer in adults. Up to half the patients develop metastases that are currently incurable, and most patients die within two years following the diagnosis of metastases. Therefore, novel therapeutic approaches are required. It has been established that tumor cells are more resistant to the hypoxia cue than non-malignant cells and can remain viable in hypoxia. Oxygen absence in hypoxic tumor areas means the absence of chemotherapeutics and the absence of the effector for radiotherapy (free oxygen radicals). To overcome this treatment resistance, we constructed MuLV-based replication-competent retroviral (RCR) vectors expressing shRNA targeting the hypoxia-response regulating genes CREB and HIF-1. These RCRs express shRNAs either against a single exon or against an exon and the poly-A signal to minimize the point-mutation resistance. These RCRs that only infect replicating cells will preferentially infect tumor cells. Pre-infected Mel270 UM subcutaneous xenografts in SCID mice were monitored weekly in vivo via bioluminescence. Here, we demonstrate that the knockdown of CREB or HIF-1 in UM cells dramatically decreases UM tumor progression. The reduction of the expression of Glut-1, which is a major glucose transporter in cancer cells, within tumors that are infected with the armed viruses may indicate UM’s dependence on glycolysis for tumor progression.