Introduction to Miniseries

Familial aggregation of haematological neoplasms: a controlled study

Advances in molecular biology techniques suggest that many haematological neoplasms originate from a transformation process at the level of the haemopoietic pluripotential stem cell. While familial aggregation has been reported for many haematological neoplasms, most studies were uncontrolled and examined the presence of the same haematological neoplasm as the index case. We assessed the familial aggregation of all haematological neoplasms in 4061 family members of 189 patients with various haematological neoplasms and two control groups: 955 relatives of 36 patients with non-malignant haematological disorders and 508 relatives of 33 patients with type II diabetes mellitus. Data collection included self-administered questionnaires. The odds ratio for haematological neoplasms among relatives of the index cases adjusted for age, sex, ethnicity, number of relatives in the family, and degree of familial linkage in the study group versus the two control groups was 3.62 (95% confidence interval, 1.44-9.07; P < 0.01). The vast majority of the haematological neoplasms among family members did not belong to the same histopathological category as the index cases. The data support the hypothesis of a genetic predisposition to haematological neoplasms. The fact that the aggregation is not disease specific is consistent with a defect in the pluripotent haemopoietic stem cell.

Primary chromosome abnormalities in human neoplasia

At the cellular level, cancer is a genetic disease; genetic changes in somatic cells are essential events in neoplasia. In a majority of cases these changes involve large enough blocks of genetic material to be visible in the microscope. The chromosome aberrations in neoplastic disorders are probably of three kinds: (1) primary abnormalities, which are essential steps in establishing the tumor; (2) secondary abnormalities, which develop only after the tumor has developed, but which nevertheless may be important in tumor progression; and (3) cytogenetic noise, which is the background level of nonconsequential aberrations. These latter changes are, in contrast to the primary and secondary changes, randomly distributed throughout the genome. The primary abnormalities, of which several dozens have now been identified, are mostly strictly correlated with particular diseases and even with histopathological subtypes within a given disease. This has been evident in the leukemias for some years already, and information now accumulating on solid tumor karyology indicates a similar situation. Clonal chromosome abnormalities are a feature of both benign and malignant neoplasms, although the changes are often less massive in the former. Apart from being clinically useful as a diagnostic technique and an aid in prognostication, tumor cytogenetics also plays a role in identifying those genomic sites which harbor genes essential in the pathogenesis of neoplastic lesions. So far, two functionally different classes of directly cancer-relevant genes have been detected, the oncogenes and antioncogenes. There is every reason to believe that future investigations with cytogenetic and recombinant DNA methods will add to our knowledge of the biology of human neoplasia, in those tumor types where the characteristic genetic change is already partially known, and by identifying hitherto unknown karyotypic abnormalities.

Oncogenes and onco-suppressor genes: their involvement in cancer

We review the involvement of two groups of genes, oncogenes and onco-suppressor genes, in malignant transformation. Approximately 40 oncogenes have been described mainly through studies on retroviruses and by in vitro functional analyses such as transfection of transforming genes into 'normal' cells. Because they are more difficult to identify, only a handful of onco-suppressor genes have been described so far, but potentially they could number as many as oncogenes. Where these genes have been isolated and sequenced, they have been shown to be highly conserved among species, suggesting that these genes play an essential role in the normal cell. Although some of properties of oncogenes have been identified, we do not know in detail the role these genes play in normal cells or how genetic damage contributes to malignancy. The effect of oncogene expression on a cell depends both on the cell type and on the oncogene, and in some circumstances oncogenes act as onco-suppressor genes and vice versa. The elucidation of the mechanism of action of oncogenes and onco-suppressor genes will not only increase our understanding of these important genes but might also provide the framework for a biological approach to the treatment of cancer.

Expression of oncogenes in human tumours with special reference to the head and neck region

A major recent advance in cancer research has been in the field of oncogenes. Oncogenes are genes with a proven cancer association and which appear to be particularly implicated in cellular regulation and proliferation. The oncogenic potential of specific cellular genes has now been recognised and this has influenced current thinking concerning the initiation of carcinogenesis. The specific role of an oncogene is still incompletely understood but research with one particular oncogene (ras) has demonstrated that it can be involved in more than one stage of multi-step carcinogenesis. New techniques are being developed and evaluated to determine the expression of specific oncogenes in normal and neoplastic tissues, with a view to using them in future diagnostic immuno-histopathological methods. This review describes the concept of oncogenes and discusses their role in the development of neoplasia. The results of the expression of various oncogenes in human malignancies with special reference to the head and neck regions are discussed. Finally, the future prospects of this research field are examined their and its possible implications in cancer therapy.

The role of the oncogene c-myc in sporadic large bowel cancer and familial polyposis coli

The human myc gene is homologous to the v-myc gene, which was discovered in the avian oncogenic retrovirus MC29. Abnormally high expression of the cellular oncogenes is suspected to be involved in nonviral carcinogenesis. This article reviews the evidence that elevated expression of the human myc gene is involved in sporadic colon carcinoma and familial polyposis coli. The abundance of myc RNA and protein is frequently higher in colorectal cancer than in normal mucosa. The mechanism of this altered expression is obscure because the structure and quantity of myc DNA are very rarely disturbed. The COLO320 cell line is discussed as one unusual example of myc DNA rearrangement and amplification. There is a correlation between tumor-specific elevated myc RNA level and location in the bowel; tumors distal to the transverse colon are more likely to have elevated myc expression. The site distribution of unselected colorectal malignancies with an elevated myc RNA level is similar to the site distribution of familial polyposis coli tumors. With this observation it is suggested that elevated myc RNA may be a marker of a distinct type of colorectal cancer that involves the same genetic events as precede familial polyposis coli cancer.

[Familial cancer. Initial results of an inquiry into its occurrence in Basel]

The initial results of a systematic study conducted in Basel on the existence of relatives with cancer in the families of more than 600 tumour patients indicate that neoplasm of all organs have forms in whose etiology genetic predisposition is an important factor. This is illustrated by the examples of mammary carcinoma, colorectal carcinoma, gastric carcinoma and lymphoproliferative diseases. Research into genetic predisposition to cancer is of practical value in order to protect persons at risk from the serious consequences of malignant tumors, and also of scientific interest because the characterisation of certain tumours can provide a fundamental insight into the pathogenesis of these diseases.

Malignant transformation of early passage rodent cells by a single mutated human oncogene

When linked to transcriptional enhancers, the mutant Ha-ras-1 gene from the T24 bladder carcinoma cell line induces the complete malignant transformation of early passage cells, while the normal Ha-ras-1 proto-oncogene only induces immortalization. Therefore, mutated Ha-ras-1 does not require a cooperating gene to trigger malignant conversion and ras genes may be involved in the process of tumorigenesis at an earlier stage than previously suspected.

Some questions on the significance of chromosome alterations in leukemias and lymphomas: a review

Recent improvement in the methods of chromosome analysis has allowed recognition of consistent chromosome alterations in several human cancers, especially leukemias and lymphomas. At the same time, newly discovered human cellular oncogenes have been mapped to individual chromosomes, with precise band assignment. Some of the assignments are coincident with the breakpoints of translocations observed in particular tumors. In fact, a relocation of the corresponding oncogenes has been observed in the cells of some of these tumors. Two notable examples are that of the t(9;22) translocation of chronic myelogenous leukemia (CML), causing the transfer of the oncogene c-abl from chromosome 9 to chromosome 22, and that of the t(8;14) translocation of Burkitt lymphoma, causing the transfer of the oncogene c-myc from chromosome 8 to chromosome 14. These findings can be taken as indicative of a critical role of chromosome alterations in the origin of cancer, through the activation of one or more cellular oncogenes, although there is no firm evidence that such an activation actually occurs. In addition, some concern exists over the validity of accepting in vitro transformation of a cell line by oncogenes as a model of carcinogenesis in man. For these reasons the question on the significance of chromosome alterations in leukemias and lymphomas should not be considered entirely settled yet. Useful models, whose study may lead to the clarification of this important point, are represented by premalignant conditions, such as the myeloproliferative disorders, where chromosome abnormalities are present before the development of a bona fide neoplasm, and by the aneuploidy syndromes, in which there exists an association between a constitutional chromosome anomaly and an increased risk of cancer.

Activation of the mouse cellular Harvey-ras gene in chemically induced benign skin papillomas

An important feature of the development of many human and animal tumours is the appearance of pre-malignant benign lesions, some of which undergo further changes during progression to malignancy. Many of the currently accepted concepts of multi-stage carcinogenesis have been developed using an experimental model based on the chemical induction of tumours in mouse skin. In this system, many of the premalignant papillomas which arise are promoter-dependent, and appear to regress if promoter treatment is interrupted, whereas others progress to form autonomous benign lesions and, in some cases, malignant carcinomas. Although the number and nature of the events leading to malignancy are not known, DNA transfection experiments have led to the identification of several genes which may be qualitatively altered in tumour cells (see ref. 6 for review). We have previously shown that DNA from transplantable mouse skin carcinomas induced by chemical carcinogens has the ability to transform NIH/3T3 cells, and that the gene responsible for the transformation is an activated form of the mouse cellular Harvey-ras gene (c-rasH). We have now investigated the stage of carcinogenesis at which the proto-oncogene acquires transforming activity. We demonstrate that primary papillomas induced by chemical carcinogens in two different mouse strains have an activated c-rasH gene. This constitutes the first report of a benign tumour which contains DNA with detectable transforming activity. In addition, steady-state levels of c-rasH gene transcripts are elevated in the papillomas as compared with normal epidermis.