Genetic Carrier Frequency for Lung Cancer

Cancer-inducing niche: the force of chronic inflammation

The growth of cancer tissue is thought to be considered driven by a small subpopulation of cells, so-called cancer stem cells (CSCs). CSCs are located at the apex of a hierarchy in a cancer tissue with self-renewal, differentiation and tumorigenic potential that produce the progeny in the tissue. Although CSCs are generally believed to play a critical role in the growth, metastasis, and recurrence of cancers, the origin of CSCs remains to be reconsidered. We hypothesise that, chronic diseases, including obesity and diabetes, establish the cancer-inducing niche (CIN) that drives the undifferentiated/progenitor cells into CSCs, which then develop malignant tumours in vivo. In this context, a CIN could be traced to chronic inflammation that involves long-lasting tissue damage and repair after being exposed to factors such as cytokines and growth factors. This must be distinguished from the cancer microenvironment, which is responsible for cancer maintenance. The concept of a CIN is most important for cancer prevention as well as cancer therapy.

Sex differences in lung cancer incidence: a genetic model

Family histories pertaining to cancer of all anatomic sites were ascertained on 88 Caucasian patients (61 males, 27 females) with histologically verified lung cancer. Lifetable analysis revealed that relatives of female probands had a significantly higher risk for cancer (all sites) at younger age (p less than .04) compared to relatives of male probands. This trend was peculiar to nonsmoking-associated cancer sites, and was not apparent for smoking-associated cancer sites. We hypothesize that certain components of genetic liability to lung cancer are common to nonsmoking-associated malignant neoplasms, and that females who develop lung cancer are more extreme with respect to genotype than are males who develop lung cancer. Our hypothesis accounts for the lower incidence of lung cancer among females, as well as the apparent increased susceptibility to cancer among their relatives.

Premorbid psychological factors as related to cancer incidence

In planning for studies relating psychological factors and/or stress (PF&/oS) to cancer, one should be aware of epidemiological findings that might contribute to or even account wholly for any found relationships. Most studies have not examined the known biological causes of cancer, nor have they described a rationale for relationships sought. The two broad mechanisms leading to cancer, carcinogens and lowered resistance to it, include physical and chemical causes, viruses and chronic infection, medication, genetic predisposition, hormonal stimuli, and aging. Interfering variables may bias or dilute a real relationship. Validity and reliability of instruments measuring PF&/oS are so variable as to warrant considerable care in their use. The latent periods of different cancers are measured in years, not months, with consequent potent impact on possible inferences drawn from prebiopsy and short prospective studies. In these and in retrospective studies, cancer can have strong and biasing effects on apparently straightforward PF&/oS measurements, as can iatrogenic effects. Some theoretical issues are discussed. The known prospective studies are discussed and reasons are given for the view that they are less convincing then many seem to think. A sketch of a model relating PF&/oS to cancer appearance is outlined, with some theoretical implications, and issues in research design are addressed.

Natural and radiation carcinogenesis in man III. Radiation carcinogenesis

The application of the author’s hypothesis of spontaneous carcinogenesis to the phenom enon of radiation carcinogenesis is described. Equations connecting the carcinogenic response to acute and chronic irradiations are derived. The effects in genetic-carriers and in noncarriers require separate consideration and further distinction is necessary between the ' short'-and 'long’-term responses. It is shown that the cytotoxic effects of ionizing radiation have to be allowed for when the short-term response to an acute irradiation is assessed, although they may generally be ignored when estimating the long-term response. However, the long-term response in a carrier subpopulation will be complicated by the magnitude of the short-term effect. The influence of age is discussed and is shown to be complicated, especially in genetic carriers. The more reliable data for radiation carcinogenesis and leukaem ogenesis in manare used in conjunction with the hypothesis to calculate α/ m s— the ratio of the radiogenic to the spontaneous mutation coefficient. The values that emerge are reasonably consistent with one another and with the independent experimental evidence relating to the radiom utability of genes in germ and somatic cells of mice.