LAUSR

Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the lethal malignancies due to the acquisition of intrinsic or acquired resistance to chemotherapeutic drugs, such as Gemcitabine (Gem). Recent evidence revealed that calcium signaling significantly contributes to Gem-associated chemoresistance (Gem resistance) in PDAC cells. Andrographis, a labdane diterpenoid isolated from the traditional herb Andrographis paniculate, is known to have a potent calcium channel-blocking potential. Accordingly, we hypothesized that Andrographis might facilitate the reversal of Gem resistance in PDAC. Methods: The critical regulatory pathways associated with the Gem resistance in PDAC were identified by analyzing publicly available cell line-based transcriptomic profiling. Gem resistant (Gem-R) PDAC cells (Gem-R MIA PaCa-2 and BxPC-3) were established by continuously culturing cells with Gem. A series of cell culture experiments were performed using Gem-R PDAC cells to evaluate the Andrographis-mediated reversal of Gem resistance in PDAC cells. At last, the cell culture findings were validated in patient-derived PDAC organoids. Results: Transcriptomic profiling identified the calcium signaling pathway as one of the key regulators of Gem resistance (Fold enrichment: 2.8, P =0.002). The combination of Andrographis and Gem revealed a superior anti-cancer potential in Gem-R PDAC cells on cell viability, clonogenicity, and migration compared to individual treatments with Andrographis or Gem. The combined treatment potentiated cellular apoptosis in Gem-R MIA PaCa-2 (Andro, Gem vs. Combination, 20.3%, 10.9% vs. 31.4%) and Gem-R BxPC-3 (Andro, Gem vs. Combination, 11.3%, 6.8% vs. 16.1%). The fluo-4 assay demonstrated that Andrographis decreased intracellular calcium concentration in Gem-R PDAC cells, while the combined treatment with Andrographis and Gem decreased its concentration more in Gem-R MIA PaCa-2 (fold change [FC] =0.79 vs. Andrographis; FC =0.54 vs. Gem) and Gem-R BxPC-3 (FC =0.80 vs. Andrographis; FC =0.73 vs. Gem). Finally, the combined treatment with Andrographis and Gem showed anti-cancer activity in patient-derived PDAC organoids. Conclusions: We have firstly investigated the Andrographis-mediated reversal of chemoresistance against Gem in PDAC cells, possibly through the regulation of cellular apoptosis and calcium signaling, using a systematic series of Gem resistant cell cultures and patient-derived tumor organoid models. Our findings could provide evidence of the combined treatment with Andrographis and Gem as a complementary therapeutic modality against PDAC. Citation Format: Keisuke Okuno, Caiming Xu, Masanori Tokunaga, Cristina Fillat, Haiyong Han, Yusuke Kinugasa, Ajay Goel. Andrographis reverses gemcitabine-associated chemoresistance by regulating calcium signaling in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3825.