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The genetic basis of pancreatic ductal adenocarcinoma, which constitutes the most common type of pancreatic malignancy, involves the sequential activation of oncogenes and inactivation of tumor suppressor genes. Among the pivotal genetic alterations are Ki-RAS oncogene activation and p53 tumor suppressor gene inactivation. We explain that the combination of these genetic events facilitates pancreatic carcinogenesis as revealed in novel three-dimensional cell (spheroid cyst) culture and in vivo subcutaneous and orthotopic xenotransplantation models. N-cadherin, a member of the classic cadherins important in the regulation of cell-cell adhesion, is induced in the presence of Ki-RAS mutation but subsequently downregulated with the acquisition of p53 mutation as revealed by gene microarrays and corroborated by reverse transcription-PCR and Western blotting. N-cadherin modulates the capacity of pancreatic ductal cells to migrate and invade, in part via complex formation with keratinocyte growth factor receptor and neural cell adhesion molecule and in part via interaction with p120-catenin. However, modulation of these complexes by Ki-RAS and p53 leads to enhanced cell migration and invasion. This preferentially induces the downstream effector AKT over mitogen-activated protein kinase to execute changes in cellular behavior. Thus, we are able to define molecules that in part are directly affected by Ki-RAS and p53 during pancreatic ductal carcinogenesis, and this provides a platform for potential new molecularly based therapeutic interventions.

Predicting the toxic potential of compounds to the ocular surface has depended on the Draize test for the past half century. Alternatives to Draize testing have recently been sought for a number of reasons. Stress gene expression has emerged as a means of quantifying cellular reaction and, thus, the toxic potential of the compound in question. This study examines the expression of the major stress response gene heme oxygenase-1 (HO-1) in a human corneal epithelial cell line (HCE-T) following challenges with a number of known ocular irritants.HCE-T was used to investigate the effect of ocular irritants on cell viability and HO-1 expression. Irritants tested included hydrogen peroxide, isopropyl alcohol, sodium hydroxide and trichloroacetic acid. HCE-T cells were grown to 80% confluency and treated with the listed irritants at a concentration range of 10-100 microM. Cell viability and northern blot analysis were performed following a 24 and 48 hr incubation period.HCE-T cells expressed HO-1 mRNA and HO activity similar to other human cell lines. Northern blot analysis demonstrated that levels of HO-1 mRNA transcripts increased regularly after exposure to the irritants in a concentration-dependent manner. Studies on the effect of various inhibitors and inducers of HO-1 on cell viability showed that inhibition of HO-1 potentiates the cytotoxic effect of ocular irritants. In contrast, pre-induction of HO-1 in HCE-T decreases the effect of various irritants on cell viability.These results are consistent with the idea that HO-1 mRNA levels may be used as an indicator of toxicity resulting from ocular irritants and that HCE-T cells respond to stress in a fashion similar to other human cell lines. This strategy for testing may be important in the development of an alternative to Draize testing. The results of this study also suggest that HO-1 may constitute a part of the protective defense mechanism against chemical injury.