Anatomical distribution of colorectal cancer over a 10 year period in a district general hospital: is there a true "rightward shift"?

Introduction: Recent studies of patients with colorectal cancer have suggested a shift towards the proximal colon and an increase in the incidence of right sided colon cancer. This study aimed to determine the anatomical distribution of colorectal cancer over a 10 year period in a district general hospital. Methods: Records of patients diagnosed with primary colorectal cancer from 1993 to 2002 were reviewed for demographic data, histology subtype, and anatomical location of the tumour. Tumours located at and proximal to the splenic flexure were defined as right sided cancer and tumours arising distal to the splenic flexure were defined as left sided cancer. Results: A total of 763 patients were included in the study, of whom all had adenocarcinoma and 99% were white. Sixty nine percent of cancers were left sided and 31% were right sided. Although there was a 4% increase in the proportion of right sided cancers, there was no statistically significant increase using logistic regression analysis. Mann-Whitney U test revealed no significant difference in age at diagnosis between the right and left sided cancers. Although a higher proportion of females were diagnosed with right sided cancer compared with left sided cancer, this was not statistically significant. Conclusion: The anatomical distribution of colorectal cancer has been fairly stable at this hospital with no evidence of a shift towards the proximal colon. No differences were identified in the tumour distribution with respect to gender and age at diagnosis. Our findings support the initial application of flexible sigmoidoscopy for investigating patients with suspected colorectal malignancy and follow up colonoscopy for selected patients to exclude right sided pathology.     

Activation-induced modification in the CD3 complex of the gammadelta T cell receptor

The T cell antigen receptor complexes expressed on alphabeta and gammadelta T cells differ not only in their respective clonotypic heterodimers but also in the subunit composition of their CD3 complexes. The gammadelta T cell receptors (TCRs) expressed on ex vivo gammadelta T cells lack CD3delta, whereas alphabeta TCRs contain CD3delta. While this result correlates with the phenotype of CD3delta(-/-) mice, in which gammadelta T cell development is unaffected, it is inconsistent with the results of previous studies reporting that CD3delta is a component of the gammadelta TCR. Since earlier studies examined the subunit composition of gammadelta TCRs expressed on activated and expanded peripheral gammadelta T cells or gammadelta TCR(+) intestinal intraepithelial lymphocytes, we hypothesized that activation and expansion may lead to changes in the CD3 subunit composition of the gammadelta TCR. Here, we report that activation and expansion do in fact result in the inclusion of a protein, comparable in mass and mobility to CD3delta, in the gammadelta TCR. Further analyses revealed that this protein is not CD3delta, but instead is a differentially glycosylated form of CD3gamma. These results provide further evidence for a major difference in the subunit composition of alphabeta- and gammadelta TCR complexes and raise the possibility that modification of CD3gamma may have important functional consequences in activated gammadelta T cells.