Enhanced DNA damage-induced p53 peptide phosphorylation and cell-cycle arrest in Sjögren's syndrome cells

[Relationship between abnormalities of genes involved in DNA damage responses and malignant tumors/autoimmune diseases]

The maintenance of genomic stability is an essential cellular function for a variety of well-coordinated regulation of biological activities of organisms, and a failure in its function results in the accumulation of mutations and/or abnormality in the induction of apoptosis, eventually leading to onsets of various diseases, including malignant tumors. DNA damage responses, in particular cell-cycle checkpoint regulation, play important roles in maintaining genomic integrity. In response to DNA damages induced by gamma-irradiation, ultraviolet irradiation, various chemicals, or reactive oxygen species (ROS), intrinsic cell-cycle checkpoint machinery is rapidly activated to arrest cells at particular cell-cycle points, and during cell-cycle checkpoint arrest cells may try to repair damaged DNAs, and then re-start cell-cycle upon the completion of DNA repair. Alternatively, if the extents of DNA damage overwhelm the capacity of the cellular repair machinery, cells may undergo apoptosis to prevent the accumulation of mutations within the organisms. In this article, we will first explain about our current view of DNA damage responses, in particular cell-cycle checkpoint regulation, and summarize our knowledge of the relationships between abnormalities of genes involved in DNA damage responses and malignant tumors, including hematopoietic malignancies. We will also discuss a possible implication of DNA damage responses in autoimmune diseases, such as rheumatoid arthritis.

Lymphoma and other malignancies in primary Sjögren's syndrome: a cohort study on cancer incidence and lymphoma predictors

OBJECTIVES

To assess the risk of lymphoproliferative disease or other malignancy (standardised incidence ratios (SIRs)), in patients with primary Sjögren's syndrome according to the American-European Consensus Criteria (AECC), compared with patients with sicca syndrome (non-AECC) and the background population. To identify predictors of malignancy and describe lymphoma types and survival probabilities.

METHODS

A linked register study using information from the Malmö Primary SS Register, Swedish Cancer Register, and Cause-of-Death Register for calculation of SIRs was carried out. Detected lymphomas were reclassified according to the WHO classification. Cox regression analysis was used to study the predictive value of clinical, laboratory, and histological findings at the time of diagnosis.

RESULTS

507 patients with a median follow up of 8 years (range 1 month to 19 years) were included. SIRs (95% confidence interval (CI)) for malignancies in total and for non-Hodgkin's lymphomas (NHL) were 1.42 (0.98 to 2.00) and 15.57 (7.77 to 27.85), respectively, in those fulfilling the AECC (n = 286). In non-AECC sicca patients (n = 221) SIR for malignancy of any kind was 0.77 (0.41 to 1.32); no lymphoproliferative neoplasms were detected. Significant predictors of lymphoproliferative disease were purpura/skin vasculitis (hazard ratio (HR) = 4.64, 95% CI 1.13 to 16.45), low complement factor C3 (HR = 6.18, 95% CI 1.57 to 24.22), low C4 (HR = 9.49, 95% CI 1.94 to 46.54), CD4+ T lymphocytopenia (HR = 8.14, 95% CI 2.10 to 31.53), and a low CD4+/CD8+ T cell ratio < or = 0.8 (HR = 10.92, 95% CI 2.80 to 41.83). 7/12 (58%) NHLs were diffuse large B cell lymphomas.

CONCLUSION

A 16-fold increased risk for development of NHL was found. CD4+ T lymphocytopenia is an additional strong risk factor for developing lymphoma.

Activation of DNA damage signaling

Cells respond to DNA damage by activating DNA repair and DNA damage signaling pathways. While DNA repair proteins directly interact with DNA lesions, activation of DNA damage signaling pathways may be triggered by the effect the DNA lesions have on replication, transcription or chromatin topology. This review will focus on the potential mechanisms of the activation of DNA damage-induced signal transduction pathways.