Hormones Genes And Cancer

Hormonal carcinogenesis is an important and controversial area of current research. In addition to accelerating existing cancers, can hormones play the role of primary carcinogens? How do genetic factors influence hormone-related cancer risk? Hormones, Genes, and Cancer addresses these questions. Over the past few decades, cancer research has focused on external environmental causes(e.g., tobacco smoke, viruses, asbestos). With the advent of new genetic sequencing techniques, we are just now beginning to understand how the body's internal environment(i.e., the hormones and growth factors that determine normal development) influences cancer etiology and prevention. From molecular insights to clinical analyses, this volume provides state-of-the-art information on the complex interactions between hormones and genes and cancer. The epidemiology and molecular endocrinology of prostate, breast, uterine, ovarian and testicular cancer are detailed in this timely treatise.

Hormonal carcinogenesis is an important and controversial area of research. In addition to accelerating existing cancers, can hormones play the role of primary carcinogens? And how do genetic factors influence hormone-related cancer risk? This work addresses these questions.

The series, Hormones in Health and Disease, was launched in 1993 to provide a scientific platform for investigators engaged in research on the biological actions of hormones and to anticipate relevance for their findings in clinical applications. The first volume of the series was dedicated to the discussion and understanding of molecular mechanisms by which steroid hormones influence target cells in normal and pathological conditions. With the diversity of information and the vast amount of literature on steroid hormone physiology, a more thorough treatment of Hormones and Cancer was identified as a timely topic. In this second volume in the series, Dr. Wayne V. Vedeckis has success fully undertaken the monumental task of editing the findings of the leading investigators in hormone and cancer research. Dr. Vedeckis brings to this project two decades of research experience in hormone action; he is actively engaged in elucidating hormone and cancer interrelations. It is a pleasure to welcome him to the series as an editor and congratulate him and all contribu tors in presenting this comprehensive treatise. The 20 chapters include discussions on contemporary topics relating control of cell division and signal transduction to the basic mechanisms of carcinogenesis by cloning patient genes, and recognizing the importance of steroid receptors in treatment protocols of various endocrine abnormalities.

Where do you begin to look for a recent, authoritative article on the diagnosis or management of a particular malignancy? The few general oncology textbooks are generally out of date. Single papers in specialized journals are informative but seldom comprehensive; these are more often preliminary reports on a very limited number of patients. Certain general journals frequently publish good in-depth reviews of cancer topics, and published symposium lectures are often the best overviews available. Unfortunately, these reviews and supplements appear sporadically, and the reader can never be sure when a topic of special interest will be covered. Cancer Treatment and Research is a series of authoritative volumes that aim to meet this need. It is an attempt to establish a critical mass of oncology literature covering virtually all oncology topics, revised frequently to keep the coverage up to date, and easily available on a single library shelf or by a single personal subscription. We have approached the problem in the following fashion: first, by dividing the oncology literature into specific subdivisions such as lung cancer, genitourinary cancer, pediatric oncology, etc.; and second, by asking eminent authorities in each of these areas to edit a volume on the specific topic on an annual or biannual basis. Each topic and tumor type is covered in a volume appearing frequently and predictably, discussing current di agnosis, staging, markers, all forms of treatment modalities, basic biology, and more.

Since our previous symposium in 1995, the pace of research in hormones and cancer has accelerated. Progress in our understanding of hormonal carcinogenic processes has been a direct result of the advances made in cell biology, endocrinology, and carcinogenesis at the molecular level. The newer fields of molecular genetics and cytogenetics already have and are expected to continue to playa major role in furthering our understanding of the cellular and molecular events in hormonal carcinogenesis. It has become increasingly clear that the risk of naturally occurring sex hormones in carcinogenic processes, both in human and in animal models, requires only minute quantities of hormones, at both the serum and tissue levels. Moreover, hormone target tissues for neoplastic transformation, perhaps with the exception of the liver, generally have relatively modest ability to metabolize sex hormones, such as the breast and prostate. Table 1 summarizes the serum, and in most cases, the tissue levels of sex hormones, both endogenously and exogenously ingested, which are associated with increased risk for endocrine-associated cancers such as breast, endometrium, and prostate, as well as the hormone levels of four experimental models that have been shown to elicit high tumor incidences. In contrast to the human, in which the hormone levels are cyclic, however, the latter require continuous hormone exposure at these relatively low levels.

Information gathered from cell-free systems, cell cultures, animal models, and human studies, together provide important insights to our understanding of hormonal cancer causation, development, and prevention; the primary objective of these Symposia. A special emphasis is placed on the two major endocrine-related cancers, that is, breast and prostate. The emerging fields of colon, lung, and pancreatic cancers in relation to hormones are examined.

Testicular cancer (TC) is the most common cancer in males aged 20-40 years, with a worldwide incidence of 7.5 per 100,000, but the rates vary considerably between countries and ethnic groups and there is evidence also for an increasing incidence in last decades. About 95% of all TCs are represented by testicular germ cell tumors (TGCTs), which include seminoma and non-seminoma histological types. It is generally assumed that the development of TGCT is under endocrine control. In particular, unbalanced androgen/estrogen levels and/or activity are believed to represent the key events for TGCT development and progression. Furthermore, recent evidence has suggested genetic association of TGCT with variations in genes involved in hypothalamic-pituitary-testicular axis and steroidogenic enzymes. This recent evidence expands the current knowledge on the role of genetic contribution in testicular cancer susceptibility, and supports the hypothesis that variations in hormone metabolism genes might change the hormonal environment implicated in testicular carcinogenesis. Therefore, hormonal carcinogenesis is an important and controversial area of current research in TGCT, and further attention is given to genetic factors influencing hormone-related cancer risk. The genetic component to TGCT is in general strong. In fact, although environmental factors clearly contribute to TGCT development (and probably to its increasing incidence in some geographical areas), the proportion of TGCT susceptibility accounted for by the genetic effects is estimated at 25%. TGCT has high familial risks compared with most other cancer types that are generally no more than two-fold: brothers of individuals with TGCT have an 8- to 12-fold increased risk of disease, and sons of affected individuals have a 4- to 6-fold increased risk. Despite this strong familial relative risk, early results from linkage studies identified a limited relationship with genetic factors, suggesting that TGCT is a genetically complex trait. However, more recently, four genome-wide association studies (GWAS) from the UK and USA have reported association of TGCTs with six new loci (KITLG, SPRY4, BAK1, DMRT1, TERT, and ATF7IP). The strongest association for TGCT susceptibility was found for SNPs in KITLG (ligand for the membrane-bound receptor tyrosine kinase KIT) gene with a greater than 2.5-fold increased risk of disease per major allele, which is the highest reported for any cancer to date. These studies are being now replicated by other researches and attention is given to the relationship between these genetic variations, TGCT risk and frequently associated anomalies of the reproductive tract, such as cryptorchidism and infertility. Finally, over the past few decades, TCGT research has focused also on external environmental causes acting mainly as endocrine disrupters of androgen and oestrogen pathways, even during the foetal development of the testis. It is well known that the testicular dysgenesis syndrome (TDS) hypothesis, proposed ten years ago, suggests that disturbed testicular development in fetal life may result in one or more of four disorders postnatally, named cryptorchidism, hypospadias, poor semen quality, and TGCT. These four disorders are therefore considered as one clinical entity and are linked together by epidemiological and pathophysiological relations. The relative contribution of genetics and environment in TGCT development, and the interactions between endocrine disruptors and variations in genes involved in hormonal carcinogenesis is therefore another interesting area of research.

The Roundtable on Environmental Health Sciences, Research, and Medicine wanted to address the link between environmental factors and the development of cancer in light of recent advances in genomics. They asked what research tools are needed, how new scientific information can be applied in a timely manner to reduce the burden of cancer, and how this can be flexible enough to treat the individual.