Increased RFC4 Expression in Hepatocellular Carcinoma.
Jie Ouyang, David E Burstein, M Isabel Fiel, Swan N Thung, Stephen C Ward. The Mount Sinai Medical Center, New York, NY
Background: Replication factor C (RFC) is a five-subunit protein complex required to coordinate leading and lagging strand DNA synthesis during S phase and DNA repair in eukaryotic cells. Genome-wide analyses and PCR studies show that RFC4 is consistently upregulated in hepatocellular carcinoma (HCC). Inhibition of RFC4 expression by siRNA correlated with decrease in HepG2 (human liver cancer cell line) proliferation, increased apoptosis and increased sensitivity to DNA-damaging chemotherapeutic agents. RFC4 may therefore be important in hepatocarcinogenesis and could serve as a novel target for cancer therapeutics. There is currently no immunohistochemical data in the literature on RFC4 protein expression in human HCC.
Design: Formalin fixed paraffin embedded tissue from 42 HCCs (12 well-, 19 moderately-, and 11 poorly-differentiated), 10 high grade dysplastic nodules (HGDN), 10 low grade dysplastic nodules (LGDN), 10 HCV related cirrhotic livers without HCC and 10 normal livers (from resection for metastasis) were stained with antibody to RFC4 (Santa Cruz Biotechnology,Inc., Santa Cruz, CA). Of the HCCs, 27 were HCV+, 9 were HBV+ and 6 were negative for both. The expression of RFC4 was graded as: 0 (negative), 1+ (weak), 2+ (moderate), or 3+ (strong) based on intensity of nuclear staining. High expression was defined as 2+, or 3+.
Results: Overall 52.4% (22/42) of HCC cases showed high expression of RFC4, compared with only 2.5% (1/39) of adjacent non-tumor liver, 0% (0/10) of normal liver, 20% (2/10) HCV-related cirrhosis, 0% (0/10) LGDN, and 10% (1/10) HGDN. High expression of RFC 4 was significantly elevated in HCC compared to adjacent non-tumor liver (p<0.0001), normal liver (p<0.005), and dysplastic nodules (p<0.0005). There was a trend toward higher expression of RFC4 in HCC compared to cirrhotic liver without tumor (p = 0.06). RFC4 high expression rate in well, moderately, and poorly differentiated HCC was 33.3%, 42.1 %, and 90.9% respectively (p=0.007; Cochran-Armitage trend test). We found that 48% (13/27) of HCV+ cases, 67% (6/9) of HBV+ cases and 67% (4/6) HBV/HCV negative cases showed high expression of RFC4. There was no significant difference in RFC4 expression based on etiology of liver disease (p=0.51).
Conclusions: We show that RFC4 expression is higher in HCC than adjacent non-tumor liver, normal liver, and dysplastic nodules. Further, increased RFC4 expression is associated with less differentiated tumors and is not specific for etiology of underlying liver disease. These data suggest that RFC4 plays a role in hepatocarcinogenesis. HCC with high RFC4 expression may benefit from novel targeted therapeutics.
Category: Liver & Pancreas
Monday, February 28, 2011 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 199, Monday Morning