| Abstract: | OBJECTIVE To develop an HCT‐8/5‐FU multidrug‐resistant colorectal cancer cell line and to elucidate the effect of Andrographolid (AG), an extract from Andrographis paniculate, a medicinal herb on the HCT‐8/5‐FU multidrug‐resistant colorectal cancer cell line. METHODS An HCT‐8 colorectal cancer cell line was used and a high concentration of 5‐Fluorouracid (5‐FU) was introduced at the beginning to induce drug resistance, then the concentration of 5‐FU was increased in gradients. Approximately 7 months later, the cells grew stably in 2.0 µg/mL of 5‐FU, and the cell line was named HCT‐8/5‐FU multidrug‐resistant colorectal cancer cell line. The resistant index of HCT‐8/5‐FU cells to 5‐FU, adriamycin (ADM), cisplatin (DDP) was checked by MTT test, and a growth curve was drawn. The morphological changes were observed by both light and electron microscope. The function of P‐170 was detected by rhodamine staining. After the application of AG and co‐administration of 5‐FU, ADM and DDP, the growth curves and inhibition rate as well as apoptosis rate of HCT‐8/5‐FU at different concentrations of AG were evaluated by MTT and flow cytometry. Rhodamine staining was used to investigate the possible mechanism involved by AG. RESULTS The resistance index of HCT‐8/5‐FU to 5‐FU was 16.6, and a cross‐resistance to ADM and DDP was noticed. Compared with parental cells, HCT‐8/5‐FU cell's growth rate did not change significantly but the cell's morphology was remarkably changed as compared with parental cells. Overexpression of P‐170 by HCT‐8/5‐FU cell was indicated through rhodamine staining. AG at a low concentration showed weak inhibitory effect on HCT‐8/5‐FU. However, a remarkable inhibitory and apoptosis rate was shown when AG was co‐administered with 5‐FU, ADM and DDP, respectively. Interestingly AG alone could not induce apoptosis and change the cell cycles. AG might affect the expression of P‐170, which was indicated by rhodamine staining. CONCLUSIONS The HCT‐8/5‐FU multidrug‐resistant colorectal cancer cell line has been successfully developed and because it has cross‐resistance to 5‐FU, ADM and DDP, it might serve as an ideal multidrug resistance (MDR) model for colorectal cancer research. The mechanism of HCT‐8/5‐FU resistance to chemotherapeutic agents might be related to the overexpression of P‐170. Low concentrations of AG alone have no significant inhibition on HCT‐8/5‐FU and fail to induce apoptosis and to change cell cycles. AG might act as a chemosensitizer when co‐administered with 5‐FU, ADM and DDP, and the mechanism of reversal modulation of multidrug resistance by AG in the HCT‐8/5‐FU resistant cell line might be related to its downregulation of overexpression of P‐170. |
