Synergistic Interactions of Atractylodes lancea Rhizome Compounds in the Treatment of Cholangiocarcinoma

Background: Cholangiocarcinoma (CCA)is the primary type of bile duct cancer with high morbidity and mortality, particularly in patients with advanced stages. Numerous studies have been carried out in efforts to discover effective cancer chemotherapeutic agents from plant sources with low toxicity. Treatment of CCA remains unsatisfactory due to the lack of sensitive and specific diagnostic tools for early detection and effective chemotherapeutics.

Purpose: The primary purpose of this study is to investigate cytotoxic interactions between the three major constituents of the rhizomes of Atractylodeslancea (Thunb)DC., i.e.,
-eudesmol (BE), atractylodin (AT), and hinesol (HS) against CCA cell line.

Methods: The bioactive constituents of AL rhizome under investigation, ie, BE, AT, HS, and 5-FU were purchased from Wako (Wako Ltd., Osaka, Japan). Cytotoxic activities against the human CCA cells CL-6 of the dual (BE:AT, BE:HS, and AT:HS) and triple (BE:AT:HS) combinations were evaluated using the assay. The cytotoxic interaction of each dual combination was assessed at five concentration ratios (10:0, 7:3, 5:5, 3:7, and 0:10) using isobologram analysis. The fractional inhibitory concentration index of each combination pair (representing combination scores) and the sum FIC of five distinctive ratios were calculated as the ratio of IC50 of the combination and that of each compound alone. For triple combination, the concentration ratio used in the experiment was 1:1.5:2.5(BE:AT:HS), and analysis of the interaction was performed using polygonogram analysis at the IC50 and IC90 concentrations (concentration that inhibits cell growth by 50% and 90%, respectively).

Results: The study was the first that confirmed the cytotoxic synergistic interaction of the three major compounds from AL rhizome on the human CCA cell line CL-6. The BE:AT combination produced the additive effect with a sum FIC (fractional inhibitory concentration) of 0.967±0.02 (mean±SD). The BE:HS and AT:HS combinations produced a synergistic effect with sum FICs of 0.685±0.08 and 0.767±0.09, respectively. The mixture of the three compounds produced synergistic interaction with CI (combination index) values of 0.519±0.10 and 0.65±0.17 (mean±SD) at the IC50 and IC90 concentration levels, respectively.

Conclusion: The multi-ingredient characteristics of the plant extract would be expected to optimize therapy regarding both efficacy (synergistic anti-CCA activity) and tolerability (buffering effect). Results obtained would guide further development of AL as a potential anti-CCA chemotherapeutics concerning the appropriate pharmaceutical dosage form.