The human c-ras1H oncogene: a mutation in normal and neoplastic tissue from the same patient

RAS mutations in human cancers: Roles in precision medicine

Ras proteins play a crucial role as a central component of the cellular networks controlling a variety of signaling pathways that regulate growth, proliferation, survival, differentiation, adhesion, cytoskeletal rearrangements and motility of a cell. Almost, 4 decades passed since Ras research was started and ras genes were originally discovered as retroviral oncogenes. Later on, mutations of the human RAS genes were linked to tumorigenesis. Genetic analyses found that RAS is one of the most deregulated oncogenes in human cancers. In this review, we summarize the pioneering works which allowed the discovery of RAS oncogenes, the finding of frequent mutations of RAS in various human cancers, the role of these mutations in tumorigenesis and mutation-activated signaling networks. We further describe the importance of RAS mutations in personalized or precision medicine particularly in molecular targeted therapy, as well as their use as diagnostic and prognostic markers as therapeutic determinants in human cancers.

RAS oncogenes: the first 30 years

From the pioneering work with acute transforming retroviruses to the current post-genomic era, RAS genes have always been at the leading edge of signal transduction and molecular oncology. Yet, a complete understanding of RAS function and dysfunction - mainly in human cancer - is still to come. The knowledge that has accumulated since their discovery 30 years ago has, however, been remarkable, and should pave the way for not only solving the outstanding issues regarding RAS biology, but also for developing efficacious drugs that could have a significant impact on cancer treatment.

Activation of Ha-ras in human chronic granulocytic and chronic myelomonocytic leukaemia

DNAs from chronic granulocytic leukaemia (CGL) and chronic myelomonocytic leukaemia (CMML) were assayed for transforming genes by transfection into NIH 3T3 cells. Foci DNA was tagged with a geneticin-resistance cosmid, then followed through a drug selection and tumorigenicity assay. Activated Ha-ras genes, with point mutations at codon 12 (glycine to valine) were subsequently detected. The mutation was detected in the original samples by either MspI/HpaII digestion or polymerase chain reaction (PCR). Although mutations in the ras gene family may occur frequently in leukaemias, these are the first examples of Ha-ras mutations in CGL (blast crisis) and CMML.

A membrane-specific tyrosinase chelate: the mitotic regulator?

Cancer's random, reversible, unstable transitions to "normal" structures imply their functional relation. Similar random, continuous, reversible oncogene "mutational transformation" also lacks a consistent hybrid. Positing cancer's "mutationally altered genotype" leads to medically foreign causes, qualities, inducers, suppressors, immune proteins, and viruses. Its random variation, however, opposes the functionally discrete, ordered, stable, irreversible hybrid variation and single-valued transforms of molecular genetics. There, "causal mutational operators" remain unspecified; only consistent single-valued DNA base and amino acid change, as "transform operand", are made explicit. A mitotically "blocked" (normal) and "unblocked" (malignant) stem cell "phenotype", operationally constructed from microscopic data, is therefore viewed within the homeostatic context of open-system enzyme-regulatory equilibrium. This functional, stochastic field distribution between "structurally bound" and "freely dividing" stem cell number discloses their putative regulatory mitotic-blocking factor. A tyrosinase complex, interacting by Cu2+-Fe2+ chelation with a proline hydroxylase divisional enzyme near stem cell ribosomes, maintains steady-state mitotic equilibrium. Based upon familiar medical, biochemical, and energy principles this confronts cancer's pigmentary-depigmentary signs, glycolytic metabolism, elevated serum tyrosinase, defective collagen production, exposed membrane binding sites, and tyrosine's recent growth control role.

Microbial oncogenesis

For more than a century, medical investigators have sought to incriminate microorganisms in the cause of cancer. The first scientific evidence of such a relationship came in 1911, with the first successful induction of a tumor using a cell-free extract. Since that time, considerable data have accrued linking retroviruses, herpes viruses, the hepatitis B virus, papovaviruses, and adenoviruses to various malignant neoplasms. There is also increasing evidence that certain bacteria and parasites participate as cofactors in the development of some cancers. Although proof of cause-and-effect relationships has been difficult to obtain, there can be little doubt that microorganisms occasionally play pivotal roles in the origin of some cancers. Whether attempted intervention against these cancers is best directed against the oncogenic microorganisms themselves or against other environmental cofactors is not yet clear. Nevertheless, the successful application of tumor vaccines in the prevention of Marek's disease in chickens and in modifying the outcome of oncogenic herpesvirus infections in nonhuman primates offers hope of at least limited application of microbial vaccines in the prevention of human cancer.

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Amplification of inter-Alu extrachromosomal DNA during cellular ageing: retraction and explanation

We reported previously the age-dependent appearance of extrachromosomal circular DNA bands hybridizing to a human DNA fragment ('inter-Alu'), isolated from a genomic cluster of AluI repeats. Such bands appeared or increased at late passage in four out of six human fibroblast strains (six out of nine cell expansions); moreover, all DNAs (9/9) obtained from peripheral lymphocytes of aged donors, but none (0/8) from young donors, revealed a non-genomic inter-Alu band at congruent to 4.8 kilobases (kb). Subsequent data extended these numbers to 16/24 aged donors compared with 0/18 young donors. These results were interpreted as evidence of age-dependent DNA rearrangement in normal human cells. We now report that the 'extra' bands were of microbial origin, although clearly occurring in an age-dependent manner.

An approach to oncological genetics

Oncological genetics is defined as a branch of clinical cancer research dealing with the identification, description, analysis, and prevention of those human neoplasias and their related/associated syndromes in which a vertical (hereditary) transmission is assumed. The present clinical basis of this field is constituted by the 240 inherited preneoplasias and neoplasias that have been detected so far. The main hypothesis in oncological genetics might be the existence of an inherited cancer proneness phenotype (CPP), in whose determination the processes involved in the activation of cellular proto-oncogenes would presumably play a role. It is conjectured that CPP is a quantitative (random) variable with extreme values. Such indicators can be identified in small populations having a structure (i.e., tree) so that the collection of comprehensive pedigree data is indispensable.

Normal cells of patients with high cancer risk syndromes lack transforming activity in the NIH/3T3 transfection assay

Oncogenes capable of transforming NIH/3T3 cells are often present in human tumors and tumor cell lines. Such oncogenes were not detected in normal fibroblast lines derived from patients with several clinical syndromes associated with greatly increased cancer risk. Thus, germ-line transmission of these oncogenes does not appear to be the predisposing factor responsible for these high cancer risk syndromes.

Mutation affecting the 12th amino acid of the c-Ha-ras oncogene product occurs infrequently in human cancer

A point mutation alters the 12th amino acid of the c-Ha-ras oncogene product p21 in a human bladder cancer cell line. This is, at present, the only mutation known to result in a human transforming gene. This mutation may therefore represent a possible target for mutagenesis leading to carcinogenesis in humans. By means of restriction enzyme analysis, 29 human cancers, including 20 primary tumor tissues, derived from organs commonly exposed to environmental carcinogens, were tested for the presence of this mutation. None of ten primary bladder carcinomas exhibited the mutation; nor did nine colon carcinomas or ten carcinomas of the lung. Thus the point mutation affecting the 12th amino acid of the c-Ha-ras gene product, while a valuable model for carcinogenesis, does not appear to play a role in the development of most human epithelial cancers of the bladder, colon, or lung.