The Fas-FasL system and colorectal tumours

Morphologic and molecular events at the invading edge of colorectal carcinomas

The mechanisms whereby colorectal carcinomas invade the extracellular matrix remain elusive. In a series of studies on the growing edge of colorectal carcinomas, we found dilated neoplastic glands, some with a layer of flat tumor cells, and some lacking one or more groups of consecutive lining tumor cells (called glandular pores). Through the glandular pores, the retained glandular material was siphoned off directly into the juxtaposed extracellular matrix. The substances secreted by the tumor cells, rich in proteolytic enzymes, disrupted the anatomy of the extracellular matrix. To remodel the defective glands, the malignant cells, proliferating from the tip of the free borders of the pores, invade the enzymatically disrupted matrix to achieve glandular continuity. Sealing of these glandular flaws permits intraglandular accumulation of new proteolytic material, a mechanism that replicates a new wave of host invasion at the invading edge, thus ensuring stepwise but everlasting tumor progression in untreated patients. More recent findings indicated that the flat tumor cells at the advancing edge failed to express the proliferation marker Ki67 but overexpressed the mutated p53 protein. This paradoxic biologic behavior of tumor cells may be connected with the subsequent formation of glandular pores and strongly suggests that the arrested cell proliferation at the advancing tumor edge occurs independently of p53 mutation. Possibly, two independent molecular systems exist at the advancing edge of colonic carcinomas, one supervising cell proliferation and the other actively transferring the mutated p53 protein to daughter cells.

Effects of vitamin E succinate on the expression of Fas and PCNA proteins in human gastric carcinoma cells and its clinical significance

AIM

To investigate the effects of vitamin E succinate (VES) on the expression of Fas and PCNA proteins as well as its clinical significance in human gastric carcinoma, and to explore the mechanism of VES-induced inhibition of gastric carcinoma cell growth.

METHODS

Immunohistochemical methods were used to detect Fas and PCNA expression both in human gastric cancer SGC-7901 cells treated with VES at different doses and in human gastric carcinoma tissues.

RESULTS

After the SGC-7901 cells were treated with VES at 5, 10, 20 mg/L for 48 h, the positive rates of Fas expression were 16%, 27% and 48%, respectively, significantly increased compared to that of control group (P< 0.05); while the positive rates of PCNA expression in groups treated with different doses of VES were 20%, 18% and 7%, respectively, which were significantly decreased compared to that of the control group (P<0.05). In human gastric carcinoma tissues, the Fas positive expression rate was 42.4%(25/59), which declined with the decrease in the degree of tumor differentiation (P<0.05) and with the existence of lymph node metastasis (P<0.001). While the PCNA positive expression rate was 91.5%(54/59), no relationship was observed between PCNA expression and clinicopathologic parameters.

CONCLUSION

VES inhibited the growth of gastric cancer cells by inducing Fas expression and inhibiting PCNA expression. It is, therefore, considered that the expression of Fas and PCNA genes, through tumor cell apoptosis and proliferation, respectively, may be useful as a clinical predictive index in the application of VES to gastric carcinoma therapy, where as Fas may be of more value than PCNA.