Abundance and state of phosphorylation of the retinoblastoma susceptibility gene product in human colon cancer |
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Authors: | Rajalakshmi Gope Mohan L Gope |
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Institution: | (1) Creighton Cancer Center, Creighton University, 24th at California Street, Criss III, Rm #358, 68178 Omaha, NE, USA |
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Abstract: | In an effort to understand the possible role of Rb in cellular growth control, we have investigated the abundance and the
state of phosphorylation of Rb protein (pRb) in normal and colon tumor cell lines as well as in matched colon tumors, adenomas
and adjoining normal colonic mucosa. Resting normal human fibroblast cell lines were found to have only unphosphorylated pRb
and phosphorylation of pRb occurred when the cells entered G1-S phase. In general, the colon tumor tissues had atleast 1.5–2.0
fold increase in the abundance of pRb and 1.5–2.5 fold increase in the percentage of its phosphorylation as compared to the
corresponding normal colonic mucosa. Whereas, the adenomas had similar pRb level and its phosphorylation status as observed
in the normal colonic mucosa. The actively growing tumor cell lines had approximately two fold higher total pRb than normal
cell lines. Although, the percentage of phosphorylated form in growing tumor cell lines as well as normal cell lines were
almost equal, it was still considerably higher than normal colonic mucosa. Moreover, DNA binding assay revealed reduced binding
affinity of pRb from colon tumor cell line SW480 as compared to the normal cell line W138. These results suggest that the
abundance of pRb and its phosphorylation level may have a role in the cellular growth control in human colonic epithelium. |
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Keywords: | Rb protein human colorectal cancers western and immuno blots phosphorylation cell cycle DNA binding |
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