Chemotherapy Side-Effects: Not All DNA Damage Is Equal

SIMPLE SUMMARY: The number of children and adults with cancer that are completely cured is still increasing thanks to effective anti-cancer therapy, but they may be confronted with the negative lasting effects of the treatment later in life. In this review, we provide an overview of major clinical symptoms and toxic side-effects observed in cancer survivors. We describe which types of anti-cancer treatments—primarily DNA-damaging chemotherapeutics—might cause these toxicities and what the (potential) underlying mechanisms are. These treatments not only damage cancer cells in their attempt at tumor killing but also harm healthy cells and tissues. Observations of side-effects in cancer patients and survivors strengthen the hypothesis that the primary induced DNA damage can lead to varying toxicities while also accelerating features of aging, depending on type and dose of chemotherapeutic, clearing method, and affected organ. ABSTRACT: Recent advances have increased survival rates of children and adults suffering from cancer thanks to effective anti-cancer therapy, such as chemotherapy. However, during treatment and later in life they are frequently confronted with the severe negative side-effects of their life-saving treatment. The occurrence of numerous features of accelerated aging, seriously affecting quality of life, has now become one of the most pressing problems associated with (pediatric) cancer treatment. Chemotherapies frequently target and damage the DNA, causing mutations or genome instability, a major hallmark of both cancer and aging. However, there are numerous types of chemotherapeutic drugs that are genotoxic and interfere with DNA metabolism in different ways, each with their own biodistribution, kinetics, and biological fate. Depending on the type of DNA lesion produced (e.g., interference with DNA replication or RNA transcription), the organ or cell type inflicted (e.g., cell cycle or differentiation status, metabolic state, activity of clearance and detoxification mechanisms, the cellular condition or micro-environment), and the degree of exposure, outcomes of cancer treatment can largely differ. These considerations provide a conceptual framework in which different classes of chemotherapeutics contribute to the development of toxicities and accelerated aging of different organ systems. Here, we summarize frequently observed side-effects in (pediatric) ex-cancer patients and discuss which types of DNA damage might be responsible.