Although
irinotecan is an important anticancer
drug for treating
colorectal cancer, its dose-dependent side effects limited its clinical application. Thus, it's important to develop low-toxic candidates to enhance the efficacy of
irinotecan.
Polyynes from genus Oplopanax were reported to possess potential anticancer effects on
colorectal cancer. Hereby, we evaluated the synergetic inhibition of human
colorectal cancer cells by combining
polyyne-enriched fraction from Oplopanax elatus (the
dichloromethane fraction of Oplopanax elatus, OED) and
irinotecan. The results showed that 5 μg/ml of OED combined with 40 μM of
irinotecan possessed significant synergetic inhibition on SW-480 cells with a combination index (CI) of 0.56. Besides, the percentage of apoptotic cells was significantly increased from 69.57% (40 μM of
irinotecan) or 72.7% (5 μg/ml of OED) to 95.6%
after treatment of OED combined with
irinotecan (OCI), suggesting OED and
irinotecan possess the synergistic apoptotic effect (P < 0.01). Furthermore,
Caspase-3 was significantly activated in OCI group (P < 0.05). Besides, the percentage of apoptotic cells of OED or/and
irinotecan significantly decreased after inhibition of
caspase-3. These data indicated that OED could enhance antiproliferative effects of
irinotecan on
colorectal cancer cells, which was related with induction of apoptosis and regulations of activity of
caspase-3.