ObjectiveTo explore the influence of Xiaoai Jiedu
prescription (XJP)-containing
serum on natural killer (NK)
cells′ lethal effect on
colon cancer cells and the molecular mechanism. MethodXJP-containing
serum (0.1%, 0.5%, 1%, 5%, 10%) was used to treat
HCT-116 cells and NK-92MI
cells respectively for 24 h, and methyl thiazolyl tetrazolium (MTT) assay was employed to detect
cell proliferation. Then, low-concentration (0.1%, 0.5%, 1%) XJP-containing
serum was selected to treat co-cultured
HCT-116 cells and NK-92MI
cells for 24 h and calcein acetoxymethyl
ester/
propidium iodide (Calcein-AM/PI) was applied to detect the
killing effect of
NK cells on
colon cancer cells.
Flow cytometry was used to detect
apoptosis of
colon cancer cells,
Western blot the expression of
apoptosis-related
proteins and
signal transducer and activator of transcription 4 (STAT4) pathway-related
proteins, and
enzyme-linked immunosorbent assay (
ELISA) the
secretion of
interferon (IFN)-γ. ResultHigh-concentration (5%, 10%) XJP-containing
serum inhibited the proliferation of HCT-116 and NK-92MI
cells (P<0.01), while low-concentration (0.1%, 0.5%, 1%) XJP-containing
serum had no obvious influence on
cell proliferation compared with the blank group. As compared with the blank group, low-concentration XJP-containing
serum enhanced the
killing activity of
NK cells against
colon cancer cells in a concentration-dependent manner (P<0.01), and induced
apoptosis of
colon cancer cells (P<0.01). Moreover, XJP-containing
serum (0.1%, 0.5%, 1%) down-regulated the expression of
B-cell lymphoma 2 (Bcl-2) and
B-cell lymphoma-extra large (Bcl-xl), and up-regulated the expression of Bcl-2-associated X (Bax) compared with the blank group (P<0.05, P<0.01). Compared with the
co-culture group, XJP-containing
serum (0.1%, 0.5%, 1%) increased the expression of p-STAT4 and IFN-γ (P<0.05).
ELISA result showed that XJP-containing
serum (0.1%, 0.5%, 1%) raised IFN-γ
secretion (P<0.01). ConclusionXJP-containing
serum can enhance the activity of
NK cells to kill
colon cancer cells. The mechanism is the likelihood that it activates STAT4 pathway, increases IFN-γ
secretion by
NK cells, down-regulates the expression of Bcl-xl and Bcl-2, and up-regulates the expression of Bax, thereby promoting the
apoptosis of
colon cancer cells.