Effects of stress on methyltransferase synthesis: an important DNA repair enzyme

Biobehavioral approaches to cancer progression and survival: Mechanisms and interventions

Over the last decade, there have been groundbreaking strides in our understanding of the multiple biological pathways by which psychosocial and behavioral factors can affect cancer progression. It is now clear that biobehavioral factors not only affect cellular immunity but both directly and indirectly modulate fundamental processes in cancer growth, including inflammation, angiogenesis, invasion, and metastasis. There is also an emerging understanding of how psychological and behavioral factors used in interventions can impact these physiological processes. This review outlines our current understanding of the physiological mechanisms by which psychological, social, and behavioral processes can affect cancer progression. The intervention literature is discussed, along with recommendations for future research to move the field of biobehavioral oncology forward.

Effects on DNA Damage and/or Repair Processes as Biological Mechanisms Linking Psychological Stress to Cancer Risk

Considerable research effort in the past several decades has focused on the impact of psychological stress, and stress hormones, on cancer progression. Numerous studies have reported that stress hormone treatment or in vivo stress exposure can enhance the growth of tumor cell lines in vitro, as well as tumors in animal models, and have begun to explore molecular mechanisms. Comparatively little research has focused on the impact of psychological stress and stress hormones on cancer initiation, in part due to inherent methodological challenges, but also because potential underlying biological mechanisms have remained obscure. In this review, we present a testable theoretical model of pathways by which stress may result in cellular transformation and tumorigenesis. This model supports our overarching hypothesis that psychological stress, acting through increased levels of catecholamines and/or cortisol, can increase DNA damage and/or reduce repair mechanisms, resulting in increased risk of DNA mutations leading to carcinogenesis. A better understanding of molecular pathways by which psychological stress can increase the risk of cancer initiation would open new avenues of translational research, bringing together psychologists, neuroscientists, and molecular biologists, potentially resulting in the development of novel approaches for cancer risk reduction at the population level.

Comparison of lymphocyte apoptotic index and qualitative DNA damage in yoga practitioners and breast cancer patients: A pilot study

BACKGROUND

Yoga is found to be effective in reducing stress levels and radiation-induced DNA damage, and improving the quality of life, in breast cancer patients. The present study was aimed at comparing the apoptotic index (AI) and DNA damage of advanced yoga practitioners with those of breast cancer patients.

MATERIALS AND METHODS

This cross-sectional pilot study compared three groups (n = 9 each) of age-matched subjects viz. (1) Carcinoma breast patients in stage II or III undergoing radiation therapy after completing three cycles of chemotherapy; (2) Senior yoga practitioners who were practicing asanas, pranayama and meditation daily for more than 10 years; and (3) Normal healthy volunteers. Peripheral blood lymphocytes were isolated, and qualitative DNA damage (QDD) and AI were evaluated by single-cell gel electrophoresis assay. Approximately 500 cells were counted in each case. Number of cells that were normal, undergoing apoptosis, and with DNA damage were categorized and percentages were calculated.

RESULTS

Data being normally distributed, one-way analysis of variance (ANOVA) showed significant interaction between groups in AI (P = 0.016) and QDD (P = 0.045). On post-hoc analysis using Scheffe test, AI was significantly lower in non-yoga volunteers as compared with the breast cancer group (P = 0.019) and QDD was significantly lower in yoga practitioners when compared with non-yoga volunteers (P = 0.047).

CONCLUSION

Cellular dysfunction (QDD) requires restorative mechanisms (AI) to restore the system to a balance. The results of this pilot study show trends, which indicate that in ill-health, there is inadequate restorative mechanisms (AI) although dysfunction (QDD) is high. Through regular practice of yoga, cellular dysfunction can be lowered, thus necessitating reduced restorative mechanisms. AI and QDD could also be useful indicators for predicting the three zones of health viz. disease, health, and positive health.

Restorative biological processes and health

Research on psychological influences on physiology primarily focuses on biological responses during stressful challenges, and how those responses can become dysregulated with prolonged or repeated exposure to stressful circumstances. At the same time, humans spend considerable time recovering from those challenges, and a host of biological processes involved in restoration and repair take place during normal, non-stressed activities. We review restorative biological processes and evidence for links between psychosocial factors and several restorative processes including sleep, wound healing, antioxidant production, DNA repair, and telomerase function. Across these biological processes, a growing body of evidence suggests that experiencing negative emotional states, including acute and chronic stress, depressive symptoms, and individual differences in negative affectivity and hostility, can influence these restorative processes. This review calls attention to restorative processes as fruitful mechanisms and outcomes for future biobehavioral research.

Depression and cancer risk: 24 years of follow-up of the Baltimore Epidemiologic Catchment Area sample

OBJECTIVE

The objective was to characterize the relationship between depression and incident cancer. Few studies have employed population-based prospective data on subtypes of cancer to address the question.

METHOD

A population-based sample of 3,177 cancer-free adults from the Baltimore Epidemiologic Catchment Area Study who have been followed for 24 years. Cox proportional hazards models were used to estimate relative hazards for both overall and subtype-specific cancers among those with a history of depression.

RESULTS

The risk set contained 334 incident cancer cases and 40,530 person-years of observation. DIS/DSM-III major depression was associated with a higher hazard for overall cancer (HR: 1.9, 95% CI: 1.2, 3.0) and a statistically significant increased hazard for breast cancer (HR: 4.4, 95% CI: 1.08, 17.6) among women. There was a positive association between history of depression and prostate cancer, but confidence bounds included the null. No reliable associations were found between colon, lung, or skin cancers and depression. The pattern of results was similar for dysphoria, but not for phobia or any other mental disorder studied.

CONCLUSIONS

Results reveal a specificity to the association between depression and hormonally mediated cancers, which provides support to hypotheses about a common biological pathway between depression and cancer. Further research can build on observational studies to examine the mechanisms through which our emotions affect our health.

THE EFFECTS OF STRESS ON DNA REPAIR CAPACITY

Research has shown that lymphocytes of high-distress patients have reduced DNA repair relative to that of low-distress patients and healthy controls. Furthermore, deficits in repair are associated with an increased risk of cancer. Using and academic stress model, we hypothesized that students would exhibit lower levels of Nucleotide Excision Repair (NER) during a stressful exam period when compared to a lower stress period. Participants were 19 healthy graduate level students. NER was measured in lymphocytes using the unscheduled DNA synthesis (UDS) assay with slide autoradiography. Contrary to prediction, mean values for NER significantly increased during the higher stress period relative to the lower stress period controlling for background differences in repair. Furthermore, lymphocytes had significantly increased repair of endogenous damage during the higher stress period. Stress appears to directly increase DNA repair. Additionally, stress may increase DNA repair indirectly by increasing damage to DNA.