Pressure is a crucial component of the cellular environment, and can lead to pathology if it varies beyond its normal range. The increased intra-ocular pressures in acute glaucoma are associated with the loss of neurons by apoptosis. Little is known regarding the interaction between pressure and apoptosis at the level of the cell. The model developed in this study examines the effects of elevated ambient hydrostatic pressure directly upon cultured neuronal lines. Conditions were selected to be within physiological limits: 100 mmHg over and above atmospheric pressure for a period of 2 hr, as seen clinically in acute glaucoma. This system can be used to investigate pressure relatively independently of other variables. Neuronal cell line cultures (B35 and PC12) were subjected to pressure conditions in specially designed pressure chambers. Controls were treated identically, except for the application of pressure, and positive controls were treated with a known apoptotic stimulus. Apoptosis was detected by cell morphology changes and by 2 specific apoptotic markers: TUNEL (Terminal transferase dUTP Nick-End Labeling) and Annexin V. These fluorescent markers were detected and quantified by automated Laser Scanning Cytometry. All techniques showed that increased pressure was associated with a greater level of apoptosis compared to equivalent controls. Our results suggest that pressure alone may act as a stimulus for apoptosis in neuronal cell cultures. This raises the possibility of a more direct relationship at the cellular level between pressure and neuronal loss.

The protein tyrosine phosphatase SHP-1 is predominantly expressed in hemopoietic cell lineages, where its function is relatively well defined. However, its expression profile also extends to certain epithelial cell types. Furthermore, the negative regulatory role of this enzyme in hemopoietic cell signaling may not apply to other systems, where positive effects on particular tyrosine kinase signaling pathways have been described. Expression of SHP-1 was therefore investigated in human breast cancer cell lines and primary breast cancers. Differential expression of SHP-1 mRNA was observed among the 19 breast cancer cell lines examined, and in an analysis of 72 primary breast cancers, SHP-1 mRNA expression was increased 2- to 12-fold relative to normal breast epithelial cells in 58% of the samples. Interestingly, a subset of the cancers also over-expressed GRB2 mRNA by 2- to 7-fold, and a significant (p < 0.01) positive correlation was observed between SHP-1 and GRB2 mRNA expression. Since these proteins can bind to each other and regulate MEK/MAP kinase activation, their co-ordinate up-regulation may amplify tyrosine kinase signaling in breast cancer cells.

The protein tyrosine phosphatase SHP‐1 is predominantly expressed in hemopoietic cell lineages, where its function is relatively well defined. However, its expression profile also extends to certain epithelial cell types. Furthermore, the negative regulatory role of this enzyme in hemopoietic cell signaling may not apply to other systems, where positive effects on particular tyrosine kinase signaling pathways have been described. Expression of SHP‐1 was therefore investigated in human breast cancer cell lines and primary breast cancers. Differential expression of SHP‐1 mRNA was observed among the 19 breast cancer cell lines examined, and in an analysis of 72 primary breast cancers, SHP‐1 mRNA expression was increased 2‐ to 12‐fold relative to normal breast epithelial cells in 58% of the samples. Interestingly, a subset of the cancers also over‐expressed GRB2 mRNA by 2‐ to 7‐fold, and a significant (p < 0.01) positive correlation was observed between SHP‐1 and GRB2 mRNA expression. Since these proteins can bind to each other and regulate MEK/MAP kinase activation, their co‐ordinate up‐regulation may amplify tyrosine kinase signaling in breast cancer cells. Int. J. Cancer 88:363–368, 2000. © 2000 Wiley‐Liss, Inc.