Diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) represent the most common and most aggressive forms of Non-Hodgkin lymphoma (NHL) respectively. Traditional chemotherapy includes (C)yclophosphamide, (H)ydroxydaunorubicin, (O)ncovin (vincristine) and (P)rednisone or (P)rednisolone (CHOP); or (R)ituximab-CHOP. However, in the past 10 years, other more targeted drugs have been developed for treatment of NHLs that includes Bruton's tyrosine kinase (BTK) inhibitors such as ibrutinib (IBN) and proteasome inhibitors such as carfilzomib (CFZ). Presently, there is a high interest in the endocannabinoid system, with specific interest in CB1 and CB2 ligands as potential therapeutic targets for both DLBCL and MCL. Cannabidiol (CBD) is a natural cannabinoid analog that has mixed affinity across CB1 and CB2 receptors; known in the literature as a CB1 antagonist and a CB2 agonist. Our previous work has demonstrated that CB1 antagonists has activity against DLBCL and MCL cell lines. Our study is aimed at comparing CBD against conventional chemotherapeutics, individually and in combination, in DLBCL and MCL cell lines. Here, we demonstrate that CBD in combination with known chemotherapeutics, ibrutinib (IBN), carfilzomib (CFZ), zanubrutinib (BGB) and tumorex (TMX), has synergistic potential in treating DLBCL and MCL cell lines. To determine the activity of CBD in comparison to IBN, cells from representative DLBCL (RC) and MCL (Mino) cell lines were plated at 5,000 cells per well. The cells were incubated for 72 hours in 20 µL medium with 10% FBS and 25 µM CBD, IBN or a combination of both. Viability assays were conducted using Celltiter-Glo Luminescent Cell Viability Assay. Experiments were performed 2-3 times independently, and each concentration was tested in triplicate. We next recreated the experiment using a different BTK inhibitor, BGB, instead of IBN. Likewise we next compared CBD to a proteasome inhibitor where cells from representative DLBCL (RC) and MCL (Mino) cell lines were plated at 5,000 cells per well. The cells were incubated for 72 hours in 20 µL medium with 10% FBS and 6 µM CBD, 10 nM CFZ, or a combination of both. Viability assays were conducted using Celltiter-Glo Luminescent Cell Viability Assay. Experiments were performed 2-3 times independently, and each concentration was tested in triplicate. We then followed by recreating the experiment using 12.5 µM of CBD, 250 nM TMX or both. Synergistic potential of CBD with conventional treatment IBN was examined at concentrations of 25μM. Data shows a marked reduction in viability when drugs are used in combination as compared to individual drug response. Combining CBD with IBN lowered the viability to under 25% as compared to control whereas, individually the drugs never fall under 75% of control. A similar pattern of synergy was demonstrated amongst CBD with BGB, CFZ and TMX respectively. This synergist effect more than likely is the result of the drugs effecting two or more different biochemical pathways. However, within keeping of our previous studies, it is a further indication of the viability of targeting the cannabinoid pathway for therapeutic intervention of malignant lymphoma cancer. Figure. Figure. Disclosures No relevant conflicts of interest to declare.

WP1066 was shown to exert its potent inhibitory activity against several types of human cancer including melanoma in vitro and in vivo via suppression of JAK2/STAT3/STAT5 activation. However, if there is any other additional molecular mechanism(s) by which WP1066 generates its anti-tumor effects remain largely unknown. Here, we report a novel function for WP1066 in inducing the degradation of both HIF-1α and HIF-1β subunits in human melanoma cells. We found constitutive activation of HIF-1α and an increased expression of hexokinase II, a down target of HIF-1α, in normoxia in 6/6 of melanoma cell lines, but not in other tumor types. Both hypoxia and cobalt chloride, a transition metal that mimics hypoxia, further increased HIF-1α protein accumulation in a time-dependent manner in WM35 and SKMEL-1 melanoma cells. WP1066 selectively decreased the constitutive and hypoxia and cobalt chloride induced increase in the level of HIF-1α in a dose-dependent manner with a half-life (T1/2) of ∼13, ∼10, and ∼10 min in WM35 cells. Moreover, WP1066 decreased the T1/2 of HIF-1α following cycloheximide treatment from ∼13 to ∼7 min suggesting that WP1066 induced HIF-1α instability is not mediated via inhibition of its translation. Further, inhibition of HIF-1α protein accumulation by WP1066 was not abolished in the presence of MG132 and proteasome inhibitor I, a potent inhibitor of the 26S proteasome, suggesting that the 26S proteasome-system is not responsible for WP1066-induced HIF-1α instability. Immunoprecipitation, confocal microscopy, and cellular fractionation analyses revealed that WP1066 induced ubiquitinylation, aggregation and degradation of HIF-1α in WM35 cells. Finally, WP1066 directly inhibits activity of rhUSP5 and rUCH-L1. Altogether, our study identified a novel function for WP1066 in inducing HIF-1 instability that may also contribute to the anti-cancer effects of WP1066 in human melanoma. Citation Format: Arumugam Jayakumar, Jana Rauvolfova, Hanying Bao, Izabela Fokt, Stanislaw Skora, Amy Heimberger, Waldemar Priebe. Blockade of HIF-1 with a small molecule inhibitor WP1066 in melanoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3251. doi:10.1158/1538-7445.AM2013-3251

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