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We recently reported several driver genes of biliary tract carcinoma (BTC) that are known to play important roles in oncogenesis and disease progression. Although the need for developing novel therapeutic strategies is increasing, there are very few BTC cell lines and xenograft models currently available for conducting preclinical studies. Using a total of 88 surgical BTC specimens and 536 immunodeficient mice, 28 xenograft models and 13 new BTC cell lines, including subtypes, were established. Some of our cell lines were found to be resistant to gemcitabine, which is currently the first choice of treatment, thereby allowing highly practical preclinical studies to be conducted. Using the aforementioned cell lines and xenograft models and a clinical pathological database of patients undergoing BTC resection, we can establish a preclinical study system and appropriate parameters for drug efficacy studies to explore new biomarkers for practical applications in the future studies.

Biliary tract carcinoma (BTC) is an extremely malignant tumor, but available treatment options are limited. Despite of needs for novel therapies, few BTC-related resources are currently available for evaluation of candidate drugs. To address this issue, we have recently established 13 cell lines from surgical specimens from Japanese BTC patients. In the present study, we evaluated four new molecular targeting agents using our BTC cell-based assay panel with 17 BTC cell lines. PI3K/mTOR dual inhibitor LY3023414 showed activity at submicromolar concentration ranges against 13 of the 17 cell lines tested, including the ones with gemcitabine insensitivity. In conclusion, we demonstrated that in vitro study with the BTC cell line panel would be an efficient approach to screen for novel therapeutic strategies. Although this is preliminary result and further investigations are required for confirmation, PI3K/mTOR inhibitor might be a potential target for BTC drug development.

Gemcitabine (GEM) and cisplatin (CDDP) combination therapy (GC) is the standard chemotherapy for advanced biliary tract cancer (BTC); however, its pharmacotherapeutic efficacy remains unclear. To investigate the effects of GC, we selected 11 from 17 BTC cell lines, according to their GEM sensitivity, to be assessed using the MTS assay. The presence of synergistic effects of GC was determined using the Bliss additivism model (BM) and the combination index (CI) at a GEM:CDDP molar ratio of 7:1; this ratio was based on the respective human renal clearances of the two drugs. The pharmacotherapeutic effects were evaluated by comparing the IC50 values for administrations of GEM alone and GC in combination. All cell lines showed synergistic effects when analyzed using the BM. Based on the CI values, strong synergism, synergism, and additive effects were seen in four, five, and two cell lines, respectively. For all four GEM-resistant cell lines, on which GC had strong synergistic effects, the pharmacotherapeutic effects of GC were disappointing, with all IC50 values > 1 µM. For the GEM-effective cell lines, on which GC had synergistic or additive effects, the IC50 values were all <1 µM, and the differences were small between the IC50s for administration of GEM alone and GC in combination. Our results suggest that GC has synergistic effects on BTC cell lines but that its pharmacotherapeutic effects are inadequate.

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334 Background: Gemcitabine (GEM) + cisplatin (CDDP) combination chemotherapy is the first choice for advanced biliary tract carcinoma (BTC). In Japan, the GEM + S-1 therapy has shown promise for the treatment of BTC. Our aim was to investigate the cytotoxic effects of GEM, CDDP and S-1 on BTC cell lines and find an immunohistochemical marker for predicting the efficacy of chemotherapy. Methods: We evaluated the efficacy of GEM, CDDP, and S-1 by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay of 17 BTC cell lines. Furthermore, we subdivided the cell lines into sensitive and insensitive groups on the basis of the sensitivity of each drug. Moreover, pairwise studies were conducted using the MTT assay, Bliss additivism model, and Combination Index for analysis. Immunohistochemical expression analysis of excision repair cross-complementation group 1 (ERCC1), thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD), orotate phosphoribosyltransferase (OPRT), and thymidine phosphorylase (TP) were also performed in each cell line to compare the results of the cytotoxic effects of CDDP and S-1. Results: In the single-agent MTT assays, among the 17 tumor cell lines, 11 were sensitive to GEM, 13 to CDDP, and 11 to S-1. In 5 cell lines, <30% of the cells showed ERCC1 expression; these lines belonged to the CDDP-sensitive group. Conversely, the cell lines with >30% ERCC1-positive cells mostly belonged to the CDDP-insensitive group. CDDP IC50 correlated with the percentage of ERCC1-positive cells (P <.05). In contrast, none of the immunohistochemical markers could be used to select a cutoff level that would point to the sensitivity to S-1. In pairwise MTT assays (combination therapy), we demonstrated the synergy of GEM with CDDP in 9 tumor cell lines (53%) and the synergy of GEM with S-1 in 4 tumor cell lines(24%). Although 3 cell lines with the synergy of GEM with CDDP showed <30% ERCC1-positive cells, there was no correlation between them. Conclusions: ERCC1 expression in <30% of cells may help to identify CDDP-sensitive tumors; however, it is unknown whether expression of ERCC1 can help to predict efficacy of treatment with GEM + CDDP.

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