Expression And Significance Of BTB/POZ-ZF Protein DPZF In Hepatocellular Carcinoma

Background & Objective:Hepatocelluar carcinoma(HCC) is one of the most prevalent malignant tumor in China. The development and progression of HCC is a complicated process involving multiple genes and transforming steps.Up to now,though over 20 genes have been found to be relative to hepatocarcinogenesis,the mechanisms underlying the development of HCC remain unclear. Therefore,searching for new HCC associated molecules may give some clues to study the mechanism of HCC.The BTB/POZ-ZF[Broad complex,Tramtrack,Bric a' brac(BTB) or poxvirus and zinc finger(POZ)-zinc finger]protein family comprises a diverse group of transcription factors. These factors are so named because of a distinct and unique N-terminal BTB/POZ domain and C-terminal DNA-binding zinc fingers domains.POZ-ZF proteins have been implicated in many biological processes,including B cell fate determination,DNA damage responses,cell cycle progression and a multitude of developmental events.Consequently,dysfunction of vertebrate POZ-ZF proteins,such as promyelocytic leukemia zinc finger(PLZF),B cell lymphoma 6(Bcl-6),has been linked to tumorigenesis.DPZF(dendritic cell-derived BTB/POZ zinc finger) is a novel BTB/POZ zinc finger gene identified from human dendritic cells(DC),which encodes a 733-residue protein with a BTB/POZ domain at the N-terminal and 4 C2H2 zinc fingers at C-terminal.It is localized on chromosome 3q27 and is widely expressed in hematopoietic tissues and nervous tissues. DPZF protein expression is detectable in lymphoid neoplasm with a molecular mass of about 100 kDa,especially in B lymphoma.It is a transcription factor may be involved in hematopoiesis,immune responses,development and oncogenesis.This research was focused on the elucidation of DPZF gene's role in the development and progression of HCC,through detecting its expression level in HCC tissues by immunohistochemistry,Western blot,RT-PCR and statistic analysis based on the clinicapathologic data.Materials & Methods:The sections of 12 normal hepatic tissues and 148 HCC tissues were collected from the East Hepatobiliary Hospital affiliated to Second Military Medical University during the year of 2003-2006.HCC patients were 122 males and 26 females,with a mean age of 52.5 years (range,23-76 years).Serum hepatitis B surface antigen(HBsAg) was positive in 113 cases. The Edmonson staging of these patients was based on the clinical and pathological diagnosis. Informed consent was obtained from each patient before operation.The expression of DPZF in the samples was detected by immunohistochemical staining,Western blot and RT-PCR.Results:Immunohistochemical staining showed that:(1)The expression of DPZF in human normal hepatic tissue was weakly positive.And it was mainly located in nucleus,occasionally in cytoplasm.(2)The expression of DPZF in HCC tissue was strongly positive.The level of DPZF expression in the HCC was higher than the corresponding para-cancerous tissues and the normal hepatic tissue(p＜0.05).And it was mainly located in nucleus,occasionally in cytoplasm.(3)The expression of DPZF in HBsAg positive HCC tissue was substantially higher than the HBsAg negative HCC tissue(p＜0.05).(4) The expression of DPZF in secondary liver cancer were negative and the expression in hilar cholangiocarcinoma and cholecyst adencarcinoma were weakly positive.Expression of DPZF was detectable in Huh7,7721,PLC,HepG2 and L02 cell lines by Western blot.Western blot and RT-PCR analysis confirmed over expression of DPZF in HCC tissues compared with corresponding para-cancerous tissues and normal liver tissues.To elucidate the significance of DPZF in HCC,its expression was correlated with various clinicopathological features.Increased DPZF expression levels in HCC were positively correlated with hepatic cirrhosis(P＜0.0001),HBV infection(P＜0.0001),portal vein invasion(P=0.019),and satellite nodules involvement(P=0.0001).Importantly,the recurrence or metastasis rates of HCCs with higher DPZF expression were markedly greater than those of HCCs with lower expression(P=0.0001,P=0.0001,respectively).However, there was no significant correlation between DPZF expression and other variable parameters, including age,gender,serum AFP level,tumor size,formation of tumor capsule and Edmonson's grade of HCC.Furthermore,Multivariate analysis confirmed that DPZF overexpression(P=0.005),male(P=0.006),larger tumor size(≥50mm)(P=0.009),and serum AFP positive(P=0.016) were the independent risk factors for the recurrence of HCC by using multivariate logistic analysis.Conclusions:1.The expression of DPZF in human normal hepatic tissue was weakly positive and it was located in nucleus,occasionally in cytoplasm.2.The expression of DPZF in HCC tissue was strongly positive.The level of DPZF expression in the HCC was higher than the corresponding para-cancerous tissues and the normal hepatic tissue.It indicated that DPZF may be associated with the genesis and development of HCC.3.The expression of DPZF in HBsAg positive HCC tissue was higher compared with HBsAg negative HCC tissue.It indicated that DPZF may be associated with the mechanism of hepatocarcinogenesis induced by infection of HBV.4.DPZF level was significantly higher(p＜0.05) in portal vein thrombus,satellite nodules,recurrence and metastasis involvement groups than in the control groups. This indicated that DPZF may be associated with the recurrence and metastasis of HCC.5.Multivariate logistic analysis confirmed higher expression of DPZF(P=0.005) was the independent risk factor for the reccurence of HCC.