Exploration of the correlations between interferon-γ in patient serum and HEPACAM in bladder transitional cell carcinoma, and the interferon-γ mechanism inhibiting BIU-87 proliferation

Purpose: Interferon-γ inhibits cancer cell proliferation and induces re-expression of different tumor suppressor genes. As a candidate, HEPACAM is almost lost in bladder transitional cell carcinoma. To our knowledge whether interferon-γ inhibits BIU-87 proliferation and re-expresses HEPACAM mRNA is still unknown. Thus, we probed the mechanism and examined the correlations between interferon-γ in patient serum and HEPACAM in bladder transitional cell carcinoma.

Materials and methods: Using enzyme-linked immunosorbent assay we measured serum interferon-γ in 27 men and 6 women, and 15 volunteers. Disease was Ta-T1 in 12 patients, T2-T4 in 21, low grade in 25, high grade in 8, primary in 13 and recurrent in 20. A total of 33 cancer and 26 adjacent tissues were examined by immunohistochemistry to detect HEPACAM protein and ensure the position. Under interferon-γ stimulation we detected BIU-87 proliferation by MTT assay. Cell cycles were examined by flow cytometry. HEPACAM mRNA expression was determined by reverse transcription-polymerase chain reaction. Western blot was used to detect p21(WAF1).

Results: Interferon-γ was remarkably low in patients with bladder transitional cell carcinoma vs volunteers (p <0.01). HEPACAM protein was highly expressed in adjacent tissue, mainly at the cytomembrane, but it was almost absent in bladder transitional cell carcinoma (p <0.01). The interferon-γ decrease in the serum of patients with bladder transitional cell carcinoma and the low HEPACAM expression in tumors correlated linearly (r = 0.899, p <0.01). In vitro interferon-γ inhibited BIU-87 proliferation (p <0.01) and slightly re-expressed HEPACAM mRNA (p <0.05). The cell cycle was arrested at G(0)/G(1) and p21(WAF1) was concurrently increased in response to interferon-γ (p <0.01).

Conclusions: Results suggest an important connection between HEPACAM and interferon-γ, which may inhibit BIU-87 proliferation through HEPACAM re-expression and p21(WAF1) up-regulation to arrest cells at the G(0)/G(1) phase.