Takeshi Tokuhisa

Overexpression of c-Ki-ras and c-fos in human pancreatic carcinomas

SummaryThe mRNA expression of protooncogenesc-Ki-ras, c-myc, andc-fos was studied in five pancreatic carcinomas and five normal pancreatic tissues using RNase protection assay and Northern blot analysis. The expression of those protooncogenes was detected in total mRNA from all specimens. However, the amounts in carcinomas and in normal tissues differed.C-Ki-ras mRNA in all the tumors was expressed up to sixfold more than in normal tissues.C-fos mRNA was also overexpressed up to tenfold in four of five tumors. In contrast,c-myc mRNA levels were varied and did not differ significantly between tumors and normal tissues. The results suggest that the overexpression ofc-Ki-ras andc-fos mRNA are implicated in the development of pancreatic adenocarcinoma.

C-fos and jun Gene Expression in Murine Precursor B Lymphocytes Developed in the lnterleukin-7-Dependent Bone Marrow Cell Culture

We analyzed the expression of c-fos and jun family gene in murine pre-B cells developed in the interleukin-7-(IL-7) dependent bone marrow cell culture. The c-fos gene was expressed in the pre-B cells. The c-fos RNA became undetectable after IgM+ B cells were developed in the culture. The c-fos expression in the pre-B cells was IL-7-dependent. However, the c-fos RNA was not induced when the pre-B cells cultured without IL-7 for 6 h were restimulated with IL-7. The expression of c-jun RNA was slightly induced in the restimulated pre-B cells. The junB and junD RNA were the steady state level in the cells. These gene products formed AP-1 molecule in the pre-B cells. These results suggest that the AP-1 plays a role in the IL-7-dependent pre-B cell development.

Inhibition of class II MHC gene expression by anti-sense RNA in transgenic mice

We have established transgenic mice carrying the anti-sense DNA to the gene encoding beta chain of the class II major histocompatibility complex (I-A) molecule. The amount of I-A molecule on splenic B lymphocytes from the mice was reduced in the presence of a large amount of the exogenous anti-sense RNA. The amount of I-A beta chain RNA was selectively reduced and inversely correlated with the amount of anti-sense RNA in the spleens. These results suggest that the I-A beta chain RNA is rapidly degraded by duplex formation with the anti-sense RNA in splenic B cells from the transgenic mice.

Deregulated c-fos augments cell proliferation of B cells mediated by lipopolysaccharide

We have examined effects of the deregulated c-fos protein on the lipopolysaccharide (LPS)-mediated B cell responses using splenic B cells from transgenic lines carrying the mouse c-fos gene under the control of the H-2K (H2-c-fos) and the inducible Mx promoter (Mx-c-fosD). High c-fos expression was induced in Mx-c-fosD B cells by LPS stimulation. DNA synthesis of the B cells from both lines was augmented depending on the amount of exogenous c-fos. This augmentation resulted in the increase of IgM and IgG2b productions in the culture. These results suggest a functional role of c-fos protein in cell cycle progression of the activated B cells.

Deregulated c-fos modulates IgG2b production of B cells mediated by lipopolysaccharide

We have examined effects of the deregulated c-fos protein on IgG2b production of B cells cultured with lipopolysaccharide (LPS) using splenic B cells from a transgenic line carrying the mouse c-fos gene under the control of the interferon alpha/beta (IFN) inducible Mx promoter (Mx-c-fosD). High c-fos expression was induced in the Mx-c-fosD B cells during the first two days of culture. DNA synthesis and IgG2b production were augmented in the culture. When IFN was added together with LPS, the high c-fos expression was prolonged until day 3 of culture. IgG2b production was remarkably suppressed. However, the production was not suppressed by upregulation of c-fos via exogenous IFN on day 4 of culture. These results suggest a regulatory effect of the c-fos protein on the differentiation of B cells to IgG2b producing cells at a distinct period.