Human cytomegalovirus-encoded US28 may act as a tumor promoter in colorectal cancer

Figure 1 US28 protein expression in colorectal cancer and adjacent noncancerous tissues. A: US28 protein expression in clorectal cancer (CRC) was significantly higher than that in adjacent noncancerous tissues; B: US28 protein was highly expressed or was diffusely positive in the cytoplasm and membranes of CRC tissues; C: Negative US28 protein expression was observed in most adjacent noncancerous tissues; D: Negative US28 protein expression was observed in all HCMV-negative colorectal carcinoma, magnification × 400.

Figure 2 US28 protein expression in colorectal cancer tissues. A: US28 protein expression was negative or low in highly differentiated colorectal cancer (CRC) tissues; B: US28 protein expression was diffuse and strong in poorly differentiated CRC tissues, magnification × 400.

Figure 3 Kaplan-Meier survival analysis according to the US28 status (n = 103). The Y-axis indicates the percentage of patients, and the X-axis depicts their survival in months. The green line represents patients with low US28 expression, who exhibited a trend of better survival, compared to patients with high US28 expression (indicated by the blue line) (P = 0.003). The mean overall survival (OS) time was 55.5 mo for the low US28 expression group and 47.4 mo for the high US28 expression group.

Figure 4 US28 expression in LOVO cells. A, B: US28 mRNA expression was positive after transfection; the NC and CON groups were negative; C, D: US28 protein expression was positive after transfection; the NC and CON groups were negative. CON: Nontransfected control group; NC: Negative control group; OE: Transfection group.

Figure 5 CCK-8 cell proliferation assays indicate that US28 gene transfection significantly enhanced proliferation. CON: Nontransfected control group; NC: Negative control group; OE: Transfection group.

Figure 6 Cell cycle analysis by flow cytometry. More LOVO cells transiently transfected with pCMV6-entry-US28 were in S phase (A) compared to the CON (B) and NC (C) groups. CON: Nontransfected control group; NC: Negative control group; OE: Transfection group.

Figure 7 Effects of US28 on the invasion capacity of LOVO cells. The OE group (A) shows more cells crossing the membrane compared with the CON (B) and NC (C) groups; The membrane-crossing cells were counted in five high-power fields of each chamber (D). The results are reported as the mean ± SD. Representative photomicrographs of the transwell results were obtained under × 200 magnification. Scale bars: 200 μm. CON: Nontransfected control group; NC: Negative control group; OE: Transfection group.

Figure 8 US28 expression caused the LOVO cells to become more resistant to cisplatin-induced cell death. OE, NC and CON group cells were treated with different concentrations of cisplatin for 48 h, and relative drug resistance was analyzed by comparison with IC₅₀ values. CON: Nontransfected control group; NC: Negative control group; OE: Transfection group.