OBJECTIVETo inquire into the influence of silencing HMGB1 expression by small interfering RNA (siRNA) on cell growth, proliferation, invasion and metastasis of colorectal cancer LoVo cells both in vitro and in vivo.

METHODSLentivirus-mediated HMGB1 siRNA was transfected into LoVo cells to silence the HMGB1 expression. The HMGB1 mRNA and protein expression after siRNA transfection was detected by RT-PCR and Western blot. MTT assay was used to observe the cell proliferation and to draw a growth curve. Cell cycle was measured by flow cytometry. The ability of invasion and speed of cell migration were evaluated by transwell chamber invasion and cell scratch assay. The influence of HMGB1 silencing on the proliferation of LoVo cells in vivo was observed in LoVo tumor-bearing nude mice.

RESULTSLentivirus-mediated siRNA was successfully transfected into colorectal cancer cell line LoVo. The expression of HMGB1 mRNA and protein in the HMGB1-siRNA group were 0.24±0.04 and 0.21±0.03, respectively. Compared with the HMGB1-siRNA-Neg group (0.82±0.13, 1.15±0.18) and control group (0.93±0.15, 1.21±0.20), the difference was significant (P<0.05). MTT assay showed that the cell proliferation in the HMGB1-siRNA group was significantly inhibited when compared with that in the HMGB1-siRNA-Neg group and control group (P<0.05). Flow cytometry showed that the proliferation index (PI) of HMGB1-siRNA group was 38.27±1.32, significantly lower than 54.66±1.74 in the HMGB1-siRNA-Neg group and 57.43±1.29 in the control group (P<0.05). The transwell assay showed that the number of penetrated cells in the HMGB1-siRNA group was 14.0±3.5, significantly lower than 51.0±6.7 in the HMGB1-siRNA-Neg group and 68.0±5.3 in the control group (P<0.05). Similarly, the scrape wound recovered significantly slower in the HMGB1-siRNA group (83.61±23.21) µm than that in the other two groups (202.86±46.46) µm and (214.58±57.38) µm(P<0.05). The nude mouse xenograft tumor experiment showed that the final tumor volume was (521±34) mm3 in the HMGB1-siRNA group, significantly smaller than that in the HMGB1-siRNA-Neg group of (763±46) mm3 and control group of (802±51) mm3 (P<0.05).

CONCLUSIONSLentivirus-mediated HMGBl-siRNA can effectively inhibit the HMGB1 expression in colorectal cancer LoVo cells both in vitro and in vivo. HMGB1 gene silencing can slow the growth of colorectal cancer cells, extend the cell proliferation cycle, decrease their invasion and migration, and significantly inhibit the growth of xenograft tumor in nude mice.