The unfolded protein response is activated in Helicobacter-induced gastric carcinogenesis in a non-cell autonomous manner.

Mucous metaplasia (MM) is an aberrant secretory phenotype that arises during Helicobacter-induced gastric carcinogenesis. HSPA5, a key modulator of the unfolded protein response (UPR) activated by endoplasmic reticulum (ER) stress is overexpressed in gastric cancer (GC). We studied activation of the UPR in MM and GC in humans and mice. We assessed RNA and protein levels of ER stress markers (HSPA5, XBP1, and CHOP) in human GC, and correlated with Helicobacter pylori (H. pylori) status, then surveyed HSPA5 in normal gastric mucosa and gastric pre-neoplasia including gastritis and intestinal metaplasia (IM). The role of H. pylori infection in the UPR was assessed by co-culture with AGS GC cells. ER stress markers in metaplasia and dysplasia from transgenic K19-Wnt1/C2mE mice and C57Bl/6 mice with chronic Helicobacter felis (H. felis) infection were compared. HSPA5 was overexpressed in 24/73 (33%) of human GC. Induction of HSPA5 and XBP1 splicing was associated with H. pylori-associated GC (P=0.007 for XBP1 splicing). HSPA5 was overexpressed in MM but not gastritis in patients with H. pylori infection. Stimulation of AGS cells with CagA-positive H. pylori suppressed HSPA5 expression and XBP1 splicing. In the normal gastric mucosa of human and mouse, HSPA5 was constitutively expressed in MIST1-positive chief cells. Increased Hspa5 and Chop expression were found in dysplasia of C57Bl/6 mice with chronic H. felis infection but was absent in spontaneous gastric dysplasia in K19-Wnt1/C2mE mice with concomitant loss of Mist1 expression, similar to that observed in H. pylori-associated human GC. Induction of the UPR in the milieu of Helicobacter-induced chronic inflammation and MM may promote neoplastic transformation of Helicobacter-infected gastric mucosa.

Lymphoid and fibroblastic cell lineages from radiosensitive cancer patients: molecular analysis of DNA double strand break repair by major non-homologous end-joining sub-pathways.

AIMS: Radiation therapy (RT) is used in the treatment of approximately half of all cancer patients. Although there have been great improvements in tumor localization and the technical accuracy of RT delivery, some RT patients still have idiosyncratic hypersensitivity to ionizing radiation (IR) in their normal tissues. Although much effort has been expended in the search for assays that could detect radiosensitive individuals prior to treatment and facilitate tailored therapy; a suitable and clinically practical predictive assay has yet to be realized. Since DNA double-strand breaks (DSB) are a major lesion caused by IR, we hypothesized that radiation hypersensitive individuals might be deficient in the repair of such lesions. METHODS: To test this hypothesis we quantitatively and functionally characterized DSB repair of the two major non-homologous end-joining (NHEJ) sub-pathways in a pilot study using a plasmid repair reconstitution assay in lymphoblastoid and fibroblast cell lines from radiosensitive cancer patients and controls. Experiments using well-characterized mammalian DSB repair mutants demonstrated the ability of the assay to distinguish NHEJ sub-pathways. The proportion of direct end-joining repair compared with that of microhomology-directed repair was used as a functional end-point of DSB repair competence in the different cell lines. RESULTS: We found that the overall level of NHEJ sub-pathway repair competency was similar in cell lines from radiosensitive patients and controls. CONCLUSION: These data suggest that this assay in these cell lineages has limited usefulness as a predictive screen for the endogenous DNA DSB repair competency of radiosensitive cancer patients' cells but can usefully characterize major cellular DSB repair phenotypes.