Uveal melanoma, which arises from melanocytes located in the uveal tract, is one of the most common primary intraocular cancers. GNAQ and GNA11 mutations, which are detected most of primary uveal melanoma, activate MAPK signaling pathway, increasing cancer cell proliferation, tumor progression and growth. BAP1 mutation is highly associated with liver metastasis and death. However, there are no good therapeutic compounds for uveal melanoma treatment in clinic. 3’-deoxyadenosine (cordycepin) is an adenosine analog which inhibits growth of several types of cancer. However, its anticancer effects have been showed in limited cancer cell lines. In addition, action mechanism of 3’deoxyadenosin is poorly understood. In this study, we found different adenosine deaminase (ADA) expression or activity affects different anticancer results in uveal melanoma. Inhibition of ADA using either siRNA or pharmacologic approaches sensitized tumors to 3’-deoxyadenosine in vitro and in vivo, resulting in increased apoptosis, reduced clonogenic capacity and slower migration of uveal melanoma cells in vitro. These potent ADA-dependent anti-tumor effects were also seen in various cancer cell lines. Therefore, we suggest the potential of adenosine deaminase (ADA) as both a biomarker predicting response to 3’-deoxyadenosine, and a target for combination therapy. Citation Format: Su-Chan Lee, Lujain Alaali, HyukJean Kwon, Mohammed Rigi, Charles G. Eberhart. Targeting adenosine deaminase enhances anticancer effects of 3'-deoxyadenosine in uveal melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1868.

Diffuse Intrinsic Pontine Glioma (DIPG) is a pediatric brain tumor characterized by epigenetic dysregulation with median survival of 9-11 months. Currently, radiation is the only therapy option, and therefore calls for a new, effective treatment method. RG2833 is a brain penetrant, selective HDAC 1/3 inhibitor. Western blot confirmed that RG2833 treatment alone downregulates the NFkB pathway in multiple DIPG cell lines. We showed that RG2833 treatment decreases expression of NFkB regulated anti-apoptotic genes XIAP, BCL-2, and BCL-XL in vitro. In vivo results in DIPG flank tumors confirmed that BCL-2 and BCL-XL expression are decreased with RG2833 treatment. We have also confirmed through Western blot that RG2833 treatment induces p16, p21, and p27 expression, which negatively regulate cell cycle progression, in multiple DIPG cell lines. RNAseq data showed that PI3K/mTOR pathway is upregulated in DIPG after RG2833 treatment. Paxalisib is a brain penetrant PI3K/mTOR inhibitor currently in clinical trials for DIPG. We hypothesized that RG2833 and paxalisib combination treatment would yield synergistic effects. RG2833 synergizes with paxalisib to suppress growth as measured by CellTiterBlue. ZIP synergy scores calculated by SynergyFinder were 10.5 for SUDIPG06 and 9.2 for HSJD007. Western blot demonstrated that combination treatment induced c-PARP and FOXO1 in the SUDIPG06 cell line, and decreased p-RB expression in HSJD007 cell line. Induction of c-PARP indicates increased apoptosis, and decreased p-RB expression indicates decreased cell proliferation. In vivo experiments evaluating the efficacy of combination treatment are in progress. Our data suggest the combination of RG2833 and paxalisib may be a promising treatment option for DIPG.

Alterations in metabolism and energy production are increasingly being recognized as important drivers of neoplasia, raising the possibility that metabolic analogs could disrupt oncogenic pathways. 3′-deoxyadenosine, also known as cordycepin, is an adenosine analog that inhibits the growth of several types of cancer. However, the effects of cordycepin have only been examined in a limited number of tumor types, and its mechanism of action is poorly understood. We found that cordycepin slows the growth and promotes apoptosis in uveal melanoma, as well as a range of other hard-to-treat malignancies, including retinoblastoma, atypical teratoid rhabdoid tumors, and diffuse midline gliomas. Interestingly, these effects were dependent on low adenosine deaminase (ADA) expression or activity. Inhibition of ADA using either siRNA or pharmacologic approaches sensitized tumors with higher ADA to cordycepin in vitro and in vivo, with increased apoptosis, reduced clonogenic capacity, and slower migration of neoplastic cells. Our studies suggest that ADA is both a biomarker predicting response to cordycepin and a target for combination therapy. We also describe a novel mechanism of action for cordycepin: competition with adenosine triphosphate (ATP) in binding to Hsp90, resulting in impaired processing of oncogenic Hsp90 client proteins.