Tumor hypoxia and reoxygenation: the yin and yang for radiotherapy

Tumor hypoxia, a common feature occurring in nearly all human solid tumors is a major contributing factor for failures of anticancer therapies. Because ionizing radiation depends heavily on the presence of molecular oxygen to produce cytotoxic effect, the negative impact of tumor hypoxia had long been recognized. In this review, we will highlight some of the past attempts to overcome tumor hypoxia including hypoxic radiosensitizers and hypoxia-selective cytotoxin. Although they were (still are) a very clever idea, they lacked clinical efficacy largely because of ‘reoxygenation’ phenomenon occurring in the conventional low dose hyperfractionation radiotherapy prevented proper activation of these compounds. Recent meta-analysis and imaging studies do however indicate that there may be a significant clinical benefit in lowering the locoregional failures by using these compounds. Latest technological advancement in radiotherapy has allowed to deliver high doses of radiation conformally to the tumor volume. Although this technology has brought superb clinical responses for many types of cancer, recent modeling studies have predicted that tumor hypoxia is even more serious because ‘reoxygenation’ is low thereby leaving a large portion of hypoxic tumor cells behind. Wouldn’t it be then reasonable to combine hypoxic radiosensitizers and/or hypoxia-selective cytotoxin with the latest radiotherapy? We will provide some preclinical and clinical evidence to support this idea hoping to revamp an enthusiasm for hypoxic radiosensitizers or hypoxia-selective cytotoxins as an adjunct therapy for radiotherapy.

A case of Menkes disease caused by novel mutation in the ATP7A gene with infantile hypertrophic pyloric stenosis / 대한소아신경학회지

Menkes disease is caused by mutations in the ATP7A gene that lead to intracellular copper transport defects and characterized by brownish twisted (kinky) hair accompanied by growth retardation and intellectual disability. Reduced nitric oxide (NO) production contributes to infantile hypertrophic pyloric stenosis (IHPS) because NO plays an important role in smooth muscle relaxation. Here we describe a case of Menkes disease and IHPS in a 72-day-old male patient with severe persistent vomiting and convulsions with a novel ATP7A mutation.