Developmental Regulation of Mitochondrial Apoptosis by c-Myc Governs Age- and Tissue-Specific Sensitivity to Cancer Therapeutics.

It is not understood why healthy tissues can exhibit varying levels of sensitivity to the same toxic stimuli. Using BH3 profiling, we find that mitochondria of many adult somatic tissues, including brain, heart, and kidneys, are profoundly refractory to pro-apoptotic signaling, leading to cellular resistance to cytotoxic chemotherapies and ionizing radiation. In contrast, mitochondria from these tissues in young mice and humans are primed for apoptosis, predisposing them to undergo cell death in response to genotoxic damage. While expression of the apoptotic protein machinery is nearly absent by adulthood, in young tissues its expression is driven by c-Myc, linking developmental growth to cell death. These differences may explain why pediatric cancer patients have a higher risk of developing treatment-associated toxicities.

Mental health disorders and solid-organ transplant recipients.

Depression affects up to 60% of solid-organ recipients and is independently associated with both mortality (hazard ratio for death of ~2) and de novo malignancy after transplantation, although the mechanism is not clear. Both pretransplantation psychosis and depression occurring more than 2 years after transplantation are associated with increased noncompliance and graft loss. It remains to be shown that effective treatment of depression is associated with improved outcomes and quality of life. Immunosuppressive drugs (especially corticosteroids and calcineurin inhibitors) and physiologic challenges can precipitate deterioration in mental health. All potential transplant candidates should be assessed for mental health problems and preexisting medical conditions that can mimic mental health problems, such as uremic, hepatic, or hypoxic encephalopathy, should be identified and treated appropriately. Expert mental health review of those with identified risk factors (such as previous suicide attempts, history of mental illness or noncompliance with medications) is advisable early in the transplant assessment process to mitigate risk and support the patient. Patients with mental health disorders, when adequately controlled and socially supported, have outcomes similar to the general transplant population. Therefore, exclusion from transplantation based on the diagnosis alone is neither ethically nor medically justified. However, it is ethically and clinically justifiable to deny access to transplantation to those who, despite full support, would have a quality of life that is unacceptable to the candidate or are likely to be noncompliant with treatment or follow-up, which would lead to graft loss.

Tobacco smoking and solid organ transplantation.

Smoking, both by donors and by recipients, has a major impact on outcomes after organ transplantation. Recipients of smokers' organs are at greater risk of death (lungs hazard ratio [HR], 1.36; heart HR, 1.8; and liver HR, 1.25), extended intensive care stays, and greater need for ventilation. Kidney function is significantly worse at 1 year after transplantation in recipients of grafts from smokers compared with nonsmokers. Clinicians must balance the use of such higher-risk organs with the consequences on waiting list mortality if the donor pool is reduced further by exclusion of such donors. Smoking by kidney transplant recipients significantly increases the risk of cardiovascular events (29.2% vs. 15.4%), renal fibrosis, rejection, and malignancy (HR, 2.56). Furthermore, liver recipients who smoke have higher rates of hepatic artery thrombosis, biliary complications, and malignancy (13% vs. 2%). Heart recipients with a smoking history have increased risk of developing coronary atherosclerosis (21.2% vs. 12.3%), graft dysfunction, and loss after transplantation. Self-reporting of smoking is commonplace but unreliable, which limits its use as a tool for selection of transplant candidates. Despite effective counseling and pharmacotherapy, recidivism rates after transplantation remain high (10-40%). Transplant services need to be more proactive in educating and implementing effective smoking cessation strategies to reduce rates of recidivism and the posttransplantation complications associated with smoking. The adverse impact of smoking by the recipient supports the requirement for a 6-month period of abstinence in lung recipients and cessation before other solid organs.