DCC and SMAD4 alterations in human colorectal and pancreatic tumor dissemination.

Chromosome 18q is lost a high proportion of colorectal and pancreatic cancers. Three candidate tumor suppressor genes, DCC, Smad4 and Smad2 have been identified in this chromosome region. DCC and Smad4 aberrations have been previously identified in pancreatic and colorectal tumors. The aim of this study was to compare the presence of concurrent genetic aberrations in DCC and neighboring Smad4 and Smad2 genes during colorectal and pancreatic distal dissemination. We have used a panel of orthotopically implanted colorectal and pancreatic xenografts and corresponding metastases. We have shown that while LOH at DCC locus occurred at a similar frequency in both tumors, diminished DCC protein expression was exclusively present in colorectal tumors harboring intragenic DCC LOH. In contrast, in pancreatic xenografts loss of DCC protein and mRNA expression was restricted to metastases. Smad4 gene aberrations were detected at a similar frequency in both tumors and were selected for during distal dissemination. Acquisition of alterations in both genes occurred independently. Our results suggest that both DCC and Smad4 contribute to pancreatic and colorectal distal dissemination. However, the role of DCC may differ between both tumor types.

Mutational analysis of RAG-1 in lymphoid malignancies.

Illegitimate recombinase activity promoted by the recombination activating RAG-1 and RAG-2 is assumed to be involved in the pathogenesis of the chromosomal translocations observed in lymphoid neoplasias. We analyzed the complete coding region of the RAG-1 gene in patients with lymphoid neoplasis using a multiple PCR-SSCP (single strand conformation polymorphism) strategy. Nine multiple myelomas, 17 non-Hodgkin's lymphomas, 18 acute lymphocytic leukemias, 37 chronic lymphocytic leukemias and 33 non-neoplastic controls were studied. To screen the entire RAG-1 gene we used primers overlapping genomic segments of the RAG-1 coding sequence (nucleotides 87 to 3311). Samples with an abnormal band pattern in the SSCP were cloned and sequenced. Successful amplification was achieved with our protocol. The multiple PCR-SSCP analysis proved to be a feasible and sensitive strategy for studying variations in the sequence of the RAG-1 gene. No mutations other than the three previously reported sequence variations were detected. Although mutations in this gene do not appear to be common in lymphoid neoplasias, it would be interesting to ascertain whether the different variant forms of RAG-1 protein have an abnormal recombinase activity.

Demonstration of HCV-RNA and HBV-DNA in the serum of HBsAg negative patients with hepatocellular carcinoma.

Forty patients with chronic liver disease and HCC were analyzed for infection with hepatitis C (HCV) and hepatitis B (HBV) viruses. All patients were negative for HBsAg, 16 were alcoholics, 6 had previous blood transfusions and 18 had sporadic chronic hepatitis. Antibodies to HCV were determined by EIA 2nd generation. HBV-DNA was detected by PCR using primers of the precore region. Analysis of HCV-RNA was done with nested PCR amplifying the 5' non-coding region of the HCV genome, using primers complementary to nucleotides 1-20 and 305-320 and nested primers complementary to nucleotides 21-31 and 271-286 of the HCV-J1. Anti-HCV were positive in 35/40 patients (87.5%). HCV-RNA was detected by PCR in 34 patients (85%) all of them positive for the anti-HCV. HCV-RNA was detected in 70.5% of the alcohol abusers, in 100% of patients with history of transfusion(s) and 94.1% of patients with cryptogenic chronic liver disease. HBV-DNA was detected in only 2 patients. In conclusion, there is a high rate of HCV and a low rate of HBV viremia detected by PCR in Spanish patients with HCC HBsAg negative. No patient without anti-HCV presents HCV-RNA. Our results suggest that persistent HCV replication may play a role in hepatic carcinogenesis, as HBV-DNA could be found in only 5% of our HCC patients.