Expression And Clinicopathologic Significance Of Progesterone-induced Blocking Factor (PIBF) In Gastric Carcinoma

Progesterone-induced blocking factor (PIBF) is produced by pregnancy lymphocytesand also by malignant tumors. The PIBF-induced Th2-dominant immune response isfavorable during pregnancy but might facilitate tumor growth by suppressing local antitumorimmune responses.MethodsRT-PCR was performed to detect mRNA of PIBF and PR in two human normal celllines and nine cancer cell lines. Immunocytochemical staining was utilized to examine thePIBF protein in cell lines. Immunohistochemical staining was performed to examine thePIBF protein in human tissue from normal stomach, stomach polyp and gastric carcinoma.The clinicopathologic correlation to the PIBF expression was evaluated in gastric carcinoma.VEGF and PCNA were also examined in gastric carcinoma by immunohistochemicalstaining.Results1. PIBF expression in cultured cellsPIBF mRNA expression exhibited in both two normal cell lines and all examinedcancer cell lines except Bel7402. Immunocytochemical staining showed that no PIBFexpression in two normal cell lines, BGC-823and SMMC7721cell lines. PIBF proteinexpression was found in other six cancer cell lines.2. PR mRNA expression in cultured cellsPR mRNA appeared in two normal and eight cancer cell lines. However, PR mRNAwas undetectable in hepatoma cell lines Bel7402.3. PIBF protein in in normal stomach，stomach polyp and gastric carcinomaNormal stomach tissues did not show any positive staining. Nevertheless, all samplesof gastric carcinoma exhibited overexpression of PIBF protein. Sections of polypsdemonstrated very weak reactivity with anti-PIBF. Positive staining exhibited in tumor cells, rather than interstitial tissues. The presence of PIBF in tumor cells mainly showed threepatterns, they were strand-like cell membrane pattern between neighboring cells, perinuclearcytoplasmic spotted staining or sand-like clump pattern close to base portion of cellularnucleus and diffuse fine granules pattern in cytoplasm. PIBF expression in cases withwhole-layer invasion was greater than that of cases with muscular-layer invasion. PIBFexpression in cases with positive lymph node metastasis was greater that of negative cases.4. PR protein expression in gastric carcinomaNo PR protein expression was observed in all cases of gastric carcinoma.5. VEGF expression in gastric carcinomaVEGF was detectable in all cases. However, no clinicopathologic correlation was found.PIBF expression in cases with high VEGF expression was greater than that of cases with lowVEGF expression.6. PCNA expression in gastric carcinomaPCNA was detectable in all cases. The expression in young and middle-aged cases wasgreater than that in old-aged cases. The expression in cases with positive lymph nodemetastasis was greater than that of negative cases. There was no PIBF expression differencebetween the cases with high PCNA expression and low PCNA expression.Conclusions：1. PIBF might serve as a tumor marker and monitor the development of gastriccarcinoma.2. PIBF expression mainly exhibits in tumor cells, rather than interstitial tissue ingastric tumor. There were three patterns of positive appearance; they are strand-like cellmembrane pattern between neighboring cells, perinuclear cytoplasmic spotted staining orsand-like clump pattern close to base portion of cellular nucleus and diffuse fine granulespattern in cytoplasm.3. PIBF expression is independent on PR presence in gastric carcinoma.