Abstract
Abstract Background: Adenoid cystic carcinoma is the most common epithelial malignancy of the lacrimal gland and has poor prognosis despite current treatment strategies. The aims of this study were to evaluate the anticancer efficacy of the dual inhibition of bromodomain proteins (by JQ1) and HDAC proteins (by SAHA or Vorinostat) in lacrimal gland adenoid cystic carcinoma (LGACC) and to elucidate the underlying mechanism of action. Methods: LGACC tissue samples were collected from patients and tissue digestion was done by a collagenase digestion method. Molecular characterization of LGACC primary cell cultures was done by immunocytochemistry. LGACC cells were treated with JQ1 and SAHA individually or in combination. The synergistic effect of JQ1 and SAHA combination was determined by the CellTiter-Glo luminescent cell viability assay using Combenefit software. Migration capability of LGACC cells after drug treatment was examined by a wound healing assays. The expression levels of genes associated with LGACC malignancy were investigated after treatment with JQ1 and SAHA for 48hrs by real time PCR. The expression of c-MYB protein was detected by western blot analysis. Results: LGACC primary cultures were successfully established in-vitro. Immunofluorescence of these cells revealed positive antigenicity for epithelial, proliferative and tumor markers such as FGFR1, MYB and NICD; slightly positive antigenicity for CK-5 and CK-7; and negative antigenicity for E-cadherin.. We found that synergism between JQ1 and SAHA was highly significant as shown by synergy matrix plot and 3D surface plot. Interestingly, migration capacity of LGACC cells was significantly (p<0.002) inhibited by the combination treatment compared to either drug alone.. Our gene expression analysis revealed that the expression levels of Notch1 (p<0.04), Hes1 (p<0.05), Hey1 (p<0.008), Maml1 (p<0.013) and CDKNB (p<0.04) were downregulated significantly in LGACC cells treated with the combination compared to single drug treatment. Furthermore, western blot analysis revealed that combination treatment significantly (p<0.05) downregulated MYB expression (0.9 fold). Currently, investigations are being conducted to evaluate the synergistic anticancer effect of JQ1 and SAHA in LGACC tumor xenografts in nude mice. Conclusion: In conclusion, we successfully generated LGACC cell lines in-vitro. Our results demonstrated that the combination of bromodomain inhibitor JQ1 and histone deacetylase inhibitor SAHA behaves in a synergistic manner and has superior anticancer activity against LGACC cancer cells via targeting the Notch pathway. Taken together, these findings indicate that LGACC is strikingly sensitive to epigenetic inhibitors, which may be quickly implemented for patient use. Citation Format: Ravi Doddapaneni, Wensi Tao, David Tse, Daniel Pelaez. Synergistic anticancer effects of epigenetic drugs JQ1 and SAHA in adenoid cystic carcinoma of the lacrimal gland [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3832.