Oncogenes and tumor-suppressing genes

Association between TP73 G4C14-A4T14 polymorphism and different cancer types: an updated meta-analysis of 55 case-control studies

OBJECTIVE

The TP73 G4C14-A4T14 variant has been associated with elevated cancer risk, but the evidence is inconclusive. We performed a meta-analysis to clarify the role of this variant in cancer development.

METHODS

Eligible literature was selected by searching PubMed, Google Scholar, Cochrane Library, and Embase. The meta-analysis was performed using Review Manager 5.4.

RESULTS

A meta-analysis of 55 case-control studies showed that the G4C14-A4T14 variant was significantly associated with overall cancer development in five genetic models, including the allele model (AM), codominant model 1 (COD1), COD2, dominant model (DM), and over-dominant model (OD). Sub-group analysis based on ethnicity showed significantly higher risks in Africans in COD2 and RM and in Whites in AM, COD2, DM, and recessive model (RM). Cancer-specific subgroup analysis identified significant risks of gynecological (ovarian, cervical, and endometrial cancer), colorectal, oral, head and neck, and other cancers. Moreover, hospital-based controls revealed significant cancer risks in the AM, COD1, COD2, DM, and RM genetic models. Our findings were confirmed by trial sequential analysis.

CONCLUSION

This meta-analysis confirmed that TP73 G4C14-A4T14 significantly elevates the overall cancer risk, especially in White, African, and hospital-based populations, and specifically predisposes individuals to gynecological, colorectal, oral, and head and neck cancers.This meta-analysis was registered at INPLASY (registration number: INPLASY202210070).

Introducing Genes into Cultured Mammalian Cells

Strategies for the delivery of genes into eukaryotic cells fall into three categories: transfection by biochemical methods, transfection by physical methods, and virus-mediated transduction. This introduction deals with the first two categories.

Transfection of Mammalian Cells with Calcium Phosphate-DNA Coprecipitates

Biochemical methods of transfection, including calcium phosphate-mediated and diethylaminoethyl (DEAE)-dextran-mediated transfection, have been used for many years to deliver nucleic acids into cultured cells. Here, we briefly review the use of calcium phosphate-DNA coprecipitates for transfection.

Genomic Alterations in Human Breast Cancer: A Review

We review and discuss data on the genetic alterations documented in human breast carcinomas at the molecular level. These alterations may result in: 1) deletion of genetic material (chromosome 11p, 13q, 3p, 1q, 17p); 2) amplification of genes or entire chromosomal segments (c-myc, c-erb-B2, locus DF3/PUM, loci on 11q13); 3) rearrangements (c-myc); 4) point mutations (c-ras). Presently available informations do not allow the development of cohesive pathogenetic models but indicate that the molecular basis of human breast cancer is heterogeneous.

Ablating all three retinoblastoma family members in mouse lung leads to neuroendocrine tumor formation

Lung cancer is a deadly disease with increasing cases diagnosed worldwide and still a very poor prognosis. While mutations in the retinoblastoma (RB1) tumor suppressor have been reported in lung cancer, mainly in small cell lung carcinoma, the tumor suppressive role of its relatives p107 and p130 is still a matter of debate. To begin to investigate the role of these two Rb family proteins in lung tumorigenesis, we have generated a conditional triple knockout mouse model (TKO) in which the three Rb family members can be inactivated in adult mice. We found that ablation of all three family members in the lung of mice induces tumorlets, benign neuroendocrine tumors that are remarkably similar to their human counterparts. Upon chemical carcinogenesis, DHPN and urethane accelerate tumor development; the TKO model displays increased sensitivity to DHPN, and urethane increases malignancy of tumors. All the tumors developing in TKO mice (spontaneous and chemically induced) have neuroendocrine features but do not progress to fully malignant tumors. Thus, loss of Rb and its family members confers partial tumor susceptibility in neuroendocrine lineages in the lungs of mice. Our data also imply the requirement of other oncogenic signaling pathways to achieve full transformation in neuroendocrine lung lesions mutant for the Rb family.

Transcriptional deregulation underlying the pathogenesis of small cell lung cancer

The discovery of recurrent alterations in genes encoding transcription regulators and chromatin modifiers is one of the most important recent developments in the study of the small cell lung cancer (SCLC) genome. With advances in models and analytical methods, the field of SCLC biology has seen remarkable progress in understanding the deregulated transcription networks linked to the tumor development and malignant progression. This review will discuss recent discoveries on the roles of RB and P53 family of tumor suppressors and MYC family of oncogenes in tumor initiation and development. It will also describe the roles of lineage-specific factors in neuroendocrine (NE) cell differentiation and homeostasis and the roles of epigenetic alterations driven by changes in NFIB and chromatin modifiers in malignant progression and chemoresistance. These recent findings have led to a model of transcriptional network in which multiple pathways converge on regulatory regions of crucial genes linked to tumor development. Validation of this model and characterization of target genes will provide critical insights into the biology of SCLC and novel strategies for tumor intervention.

Origins, genetic landscape, and emerging therapies of small cell lung cancer

Lung cancer is the leading cause of cancer deaths, with small cell lung cancer (SCLC) representing the most aggressive subtype. Standard treatments have not changed in decades, and the 5-year survival rate has remained <7%. Genomic analyses have identified key driver mutations of SCLC that were subsequently validated in animal models of SCLC. To provide better treatment options, a deeper understanding of the cellular and molecular mechanisms underlying SCLC initiation, progression, metastasis, and acquisition of resistance is required. In this review, we describe the genetic landscape of SCLC, features of the cell of origin, and targeted therapeutic approaches.

Anterior skull base surgery for secondary malignancies in retinoblastoma survivors: report of two cases

With the improved survival rate of patients with retinoblastoma, the incidence of second malignancies has become substantial. We had two retinoblastoma survivors with secondary malignancies in the naso-ethmoidal complex, one a 21-year-old man with anaplastic carcinoma and the other a 16-year-old girl with malignant fibrous histiocytoma. They underwent repeated craniofacial surgery. Secondary malignancies arising at the nose and ethmoidal cells often invade the anterior skull base. The introduction of skull base surgery has provided wider surgical margins and increased the resultant likelihood of cure. Both patients have so far shown no evidence of recurrence.

The synthetic androgen mibolerone induces transient suppression of the transformed phenotype in an androgen responsive human prostatic carcinoma cell line

The synthetic androgen mibolerone elicits a set of distinct changes in the behaviour of an androgen responsive human prostatic carcinoma cell line (LNCaP). Inhibition of cell proliferation, induction of morphological change and of a prostate specific mRNA, and inhibition of colony formation in soft agar are induced by very low concentrations of mibolerone. The natural androgen dihydrotestosterone is much less effective. The changes in growth characteristics and morphology are reverted by excess antiandrogen, i.e. cyproterone acetate or hydroxyflutamide. Cell lines lacking androgen receptors (PC-3, DU 145 and MRC-5) are completely unresponsive to mibolerone. Taken together, our results indicate androgen receptor mediated suppression of the transformed phenotype in LNCaP cells.

Biologic and clinical significance of cytokine production in B-cell malignancies

Cytokines are a group of polypeptide hormones endowed with pleiotropic biological properties. Normal B lymphocytes produce a number of these factors that subserve important regulatory functions in the combined processes of proliferation and differentiation. Also neoplastic B cells can release cytokines and, simultaneously, respond to the same factors in an autocrine circuit that supports their malignant growth. In addition, tumor cells can make use of the factors released by normal cells, either spontaneously or under the influence of inductive signals from the neoplastic cells. Inappropriate or excessive release of cytokines may have an important role in the pathophysiology of some clinical features. Thus, neutralization of cytokine biologic activity in vivo could be a therapeutic strategy for treatment of human B-cell neoplasias.

miRNAs in cancer: approaches, aetiology, diagnostics and therapy

MicroRNAs (miRNAs) are causing tremendous excitement in cancer research. MiRNAs are a large class of short non-coding RNAs that are found in many plants, animals and DNA viruses and often act to inhibit gene expression post-transcriptionally. Approximately 500 miRNA genes have been identified in the human genome. Their function is largely unknown, but data from worms, flies, fish and mice suggest that they have important roles in animal growth, development, homeostasis and disease. MiRNA expression profiles demonstrate that many miRNAs are deregulated in human cancers. MiRNAs have been shown to regulate oncogenes, tumour suppressors and a number of cancer-related genes controlling cell cycle, apoptosis, cell migration and angiogenesis. MiRNAs encoded by the mir-17-92 cluster have oncogenic potential and others may act as tumour suppressors. Some miRNAs and their target sites were found to be mutated in cancer. MiRNAs may have great diagnostic potential for human cancer and even miRNA-based cancer therapies may be on the horizon.

The Drosophila cyclin D-Cdk4 complex promotes cellular growth

Mammalian cyclin D-Cdk4 complexes have been characterized as growth factor-responsive cell cycle regulators. Their levels rise upon growth factor stimulation, and they can phosphorylate and thus neutralize Retinoblastoma (Rb) family proteins to promote an E2F-dependent transcriptional program and S-phase entry. Here we characterize the in vivo function of Drosophila Cyclin D (CycD). We find that Drosophila CycD-Cdk4 does not act as a direct G(1)/S-phase regulator, but instead promotes cellular growth (accumulation of mass). The cellular response to CycD-Cdk4-driven growth varied according to cell type. In undifferentiated proliferating wing imaginal cells, CycD-Cdk4 caused accelerated cell division (hyperplasia) without affecting cell cycle phasing or cell size. In endoreplicating salivary gland cells, CycD-Cdk4 caused excessive DNA replication and cell enlargement (hypertrophy). In differentiating eyes, CycD-Cdk4 caused cell enlargement (hypertrophy) in post-mitotic cells. Interaction tests with a Drosophila Rb homolog, RBF, indicate that CycD-Cdk4 can counteract the cell cycle suppressive effects of RBF, but that its growth promoting activity is mediated at least in part via other targets.

Aging, increasing genomic entropy, and neurodegenerative disease

The genome, as biologic information, can be conceptualized in terms of entropy. The second law of thermodynamics dictates that entropy must increase over time. Consequently, aging can be viewed as increasing genomic entropy. Genetic instability is the biophysical correlate of increasing genomic entropy. Rates of increasing genomic entropy can be determined from age-specific mortality rate dynamics (e.g., Parkinson's disease and amyotrophic lateral sclerosis). These observations are consistent with a model of neurodegenerative disease as a manifestation of increasing genomic entropy with aging.

Fluorescence-based polymerase chain reaction-single-strand conformation polymorphism analysis of p53 gene by capillary electrophoresis

Mutation of the p53 gene plays an important role in neoplastic progression in human tumorigenesis. Polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) techniques are now available for the detection of point mutations. The original method using polyacrylamide gel electrophoresis is disadvantageous, particularly for clinical tests and for analysis of large numbers of samples. Therefore, using an automated capillary electrophoresis (CE) technique with a molecular-sieving polymer solution, we have devised a completely automatic fluorescence-based PCR-SSCP system (CE-FSSCP) for the differential detection of point mutations that dose not require SSCP with radioisotopes and polyacrylamide gels. The automatic CE-FSSCP system was developed for reproducible operations in the denaturation of double-stranded DNA and electrophoresis of single-stranded DNA. The detection system consists of a 100 W I2 lamp and photomultiplier. We performed CE-FSSCP with a 2% linear polyacrylamide polymer solution containing 5% glycerol. Four tissue specimens of lung tumors with mutations in exon 7 of the p53 gene were found to have mutant alleles; six-base-pair deletion at codons 247-248, a one-base-pair deletion at codon 260, a one-base-pair deletion at codon 244 and a GGC to CGC substitution at codon 244. We expect this technique to prove useful for the clinical DNA diagnosis of human cancers, determination of the therapeutic effect of anticancer agents and for the study of the molecular aspects of the mechanisms involved in the pathogenesis of human cancers.

Tumor suppressor genes and medulloblastoma

Although primary intracranial neoplasms are the most common type of solid cancer in children, little is known about their etiology at the molecular genetic level. Recently, studies have shown that a class of genes known as tumor suppressors play an important role in the origin of several different types of human tumors, including those located in the central nervous system (CNS). Using a variety of techniques, selective loss of DNA sequences has been identified in tissue specimens from children with medulloblastoma, one of the most common pediatric brain tumors. The most consistent losses to date have been shown for probes located on distal chromosome arm 17p. Although the known tumor suppressor p53 is located on this chromosome, and deletion and mutation of the p53 gene are the most common genetic events in human cancers of many types, such alterations have been infrequently detected in medulloblastoma specimens. These results suggest that inactivation of another tumor suppressor gene or genes located on 17p is important in medulloblastoma tumorigenesis. Deletion of 17p has also been shown to have implications for clinical management, as the loss of DNA sequences located on this chromosome arm is strongly associated with a negative prognosis for these patients. The identification and cloning of this tumor suppressor gene or genes will aid in understanding of the pathogenesis of medulloblastoma, as well as guiding the development of novel and more effective strategies for a cure.

A dominant inhibitory mutant of the type II transforming growth factor beta receptor in the malignant progression of a cutaneous T-cell lymphoma

In many cancers, inactivating mutations in both alleles of the transforming growth factor beta (TGF-beta) type 11 receptor (TbetaRII) gene occur and correlate with loss of sensitivity to TGF-beta. Here we describe a novel mechanism for loss of sensitivity to growth inhibition by TGF-beta in tumor development. Mac-1 cells, isolated from the blood of a patient with an indolent form of cutaneous T-cell lymphoma, express wild-type TbetaRII and are sensitive to TGF-beta. Mac-2A cells, clonally related to Mac-1 and isolated from a skin nodule of the same patient at a later, clinically aggressive stage of lymphoma, are resistant to TGF-beta. They express both the wild-type TbetaRII and a receptor with a single point mutation (Asp-404-Gly [D404G]) in the kinase domain (D404G-->TbetaRII); no TbetaRI or TbetaRII is found on the plasma membrane, suggesting that D404G-TbetaRII dominantly inhibits the function of the wild-type receptor by inhibiting its appearance on the plasma membrane. Indeed, inducible expression, under control of a tetracycline-regulated promoter, of D404G-TbetaRII in TGF-beta- sensitive Mac-1 cells as well as in Hep3B hepatoma cells results in resistance to TGF-beta and disappearance of cell surface TbetaRI and TbetaRII. Overexpression of wild-type TbetaRII in Mac-2A cells restores cell surface TbetaRI and TbetaRH and sensitivity to TGF-beta. The ability of the D404G-TbetaRH to dominantly inhibit function of wild-type TGF-beta receptors represents a new mechanism for loss of sensitivity to the growth-inhibitory functions of TGF-beta in tumor development.

Radium in drinking water and risk of bone cancer in Ontario youths: a second study and combined analysis

OBJECTIVES

Radium induces bone sarcomas at high doses, but there is controversy about risk at low doses. A previous study in Ontario found an association between the presence of radium in birthplace water supplies and an increased risk of death from bone cancer in young people. An investigation was performed to test the findings of the previous study with an independent group of subjects for whom complete information on radium exposure would be obtained.

METHODS

A population based case-control study (238 cases; 432 controls) was conducted with incident cases of bone sarcoma identified from the Ontario cancer registry. Residential histories were collected by questionnaire and water samples were obtained and analysed for radium content.

RESULTS

There was an association between risk of osteosarcoma and birthplace exposures (odds ratios (ORs) and 90% confidence intervals (90% CIs) 1.77 (1.03-3.00) but not with lifetime measures of exposure. When lifetime exposure was dichotomised, the OR was 1.31 (0.76-2.24) for osteosarcoma. There was no trend with increasing exposure. Bootstrap resampling was used to simulate lifetime doses in a pooled analysis of 1293 subjects from the two Ontario studies. The ORs were 1.38 (1.08-1.73) for all sarcomas, and 1.44 (1.01-1.87) for osteosarcoma. Geometric mean doses in bone were about 26 mRad.

CONCLUSIONS

An association was found between the presence of radium in birthplace water supplies and increased risk of bone sarcoma in two studies. Increased risk was present for lifetime measures of exposure, but the association was not significant, and there was no dose-response trend. Our findings are compatible with the absence of risk at low doses, but they might also reflect inadequate statistical power to measure a true risk at environmental exposure levels. If the increased risk at environmental doses is causal, risk of bone sarcoma is effectively linearly related to dose over five orders of magnitude.

Genomania of p53 protein in gastric cancer

The role of oncogenes and tumor suppressor genes in the pathogenesis of gastric cancer has recently received considerable attention. p53 is a tumor suppressor gene that is essential in the cell cycle; it prevents G1/S phase transition, after exposure to ionizing radiation or DNA-damaging chemotherapy. This allows the cell to repair its DNA or, if the damage is irreversible, to elicit apoptotic cell death. p53 mutations are seen in many human tumors including gastric carcinoma. Evidence suggests that mutant p53 is associated with shorter life expectancy in gastric, breast, lung, and colorectal cancer. A number of studies have shown cellular resistance to chemotherapy in the presence of mutant p53. Currently, increasing interest has been devoted to the potential role of mutant p53 as a screening tool.

Monoclonal origins of malignant mixed tumors (carcinosarcomas). Evidence for a divergent histogenesis

Malignant mixed tumors (carcinosarcomas) are examples of unusual neoplasms whose occurrences have been observed in increasingly diverse sites but whose pathogenesis remains a complete mystery. Two antithetical hypotheses that have been advanced to explain the histogenesis of these tumors include the convergence hypothesis, which proposes an origin from two or more stem cells (multiclonal hypothesis), and the divergence hypothesis, which proposes an origin from a single totipotential stem cell that differentiates into separate epithelial and mesenchymal directions (monoclonal hypothesis). To test these hypotheses, a novel strategy for the determination of clonality from as few as 100 tumor cells obtained by enzymatic digestion of either fresh or formalin-fixed, paraffin-embedded tissues and cell sorting was used that exhibited the polymerase chain reaction (PCR) in amplifying a 511-bp region located within the first intron of the human hypoxanthine phosphoribosyl transferase gene, a site that contains inactive X chromosomal obligately methylated HpaII/MspI sites and single-base allelic polymorphisms in 5% females. Carcinoma cells gated on the basis of fluorescein isothiocyanate (FITC)-anti-cytokeratin and sarcoma cells gated on the basis of FITC-antivimentin or FITC-anti-desmin were sorted to homogeneity on FACSTAR and then subjected to genomic DNA extraction and Hpa II digestion before PCR amplification and subsequent analysis of the product on denaturing gradient gel electrophoresis. The comigrations of the single homoduplexes generated from both the carcinoma cells and sarcoma cells in six different malignant mixed tumors obtained from four different organs indicated clonal identity and monoclonality in all cases. These findings of monoclonality were confirmed independently by two other methods of clonality determination. The findings of a monoclonal origin of carcinosarcomas support the single totipotential stem-cell-divergence hypothesis.

Suppression of cellular proliferation using p53 DNA recognition site-related oligonucleotides

A number of oligonucleotides were designed to bind through Hoogsteen triple helix or Watson-Crick hydrogen bonds to the p53 consensus sequence homology localized within the human nontranscribed rRNA spacer region. The oligomers, which bind in vitro to the consensus sequence homology, function as p53 analogues in cells deficient in wild-type p53 protein. Oligomers suppress proliferation of human colon cancer cells by three to eightfold, but only suppress proliferation of normal human mesangial cells or lung fibroblasts by less than 50%. On the basis of these studies, p53 analogues may be used therapeutically to selectively modify proliferation of transformed cells.

The last revised "Euro-American classification" of lymphoid leukemias and non-Hodgkin's lymphomas: the same inaccuracies and inconsistencies in a chaotic complexity

After a review of the recent physiologic, cellular genetic and molecular genetic acquisitions, a critical comment of the proposed classification is presented concerning especially a) the inclusion in the so-called "precursor B-lymphoblastic leukemias", which are pre-B neoplasias, of Burkitt's leukemic lymphoma, the cells of which are sIg+, hence B and not pre B; b) the inclusion in the chronic B lymphocytic leukemia of the so-called Galton's "prolymphocytic" leukemia, the cells of which are also sIg+, thus B and not pro B. In fact, the transformed blastoid medium size cells of this leukemia present the markers of the plasmablasts, which are the precursors of the long-lived plasma cells and migrate from the lymphoid tissue T-zone to bone marrow, where they secrete IgD, or G, or E, or to the mucosae, where they secrete IgA. Thus the so called "B-prolymphocytic leukemia" is the leukemic conversion of the (blastoid medium size cell) plasmablast lymphoma. There is in the new classification, a "large cell lymphoma" entity, which makes redundance with the "large cell follicle centre lymphoma". This large cell lymphoma representes a heterogen complex, as it includes the B-immunoblastic lymphoma which is not presented as an entity. As far as T lymphomas are concerned, it is not indicated that the CD8 cells may be CD57 + or - , and CD28 + or -. It could be mentioned that the cytotoxic T-cells are CD8+ C57- CD28+, while the suppressor T-cells are CD8+ CD57+ CD28-.

Hepatitis C virus replication is associated with expression of transforming growth factor-alpha and insulin-like growth factor-II in cirrhotic livers

The molecular role of hepatitis C virus (HCV) in liver disease has yet to be clarified. In this study, we analyzed the relationship of HCV replication with mRNA expression of growth factors and mutation of tumor suppressor gene, ie, transforming growth factor-beta 1 (TGF-beta 1), which promotes cirrhotic changes; TGF-alpha, insulin-like growth factor-II (IGF-II), which are both related to hepatocyte transformation; and tumor suppressor gene p53, which is associated with HCC progression. A semiquantitative RNA polymerase chain reaction (RNA-PCR) was used to analyze genetic expression in 31 cirrhotic liver specimens from patients with HCV. In order to detect HCV replication, the minus-strand RNA of HCV, which serves as a template for the synthesis of genomic plus-strand RNA, was examined. The expression of the growth factors was semiquantified by RNA-PCR, and the mutation of p53 was detected using PCR-single-strand conformation polymorphism. According to the semiquantitative analysis, HCV replication was not associated with the expression of TGF-beta 1 but was significantly so with the overexpression of TGF-alpha (r = 0.74) and IGF-II (r = 0.65) in the HCV-positive cirrhotic livers. No mutation of p53 was recognized in any of the samples. Our investigation thus suggested that the replication of HCV might mediate the coexpression of TGF-alpha and IGF-II and act as a possible initiating factor for hepatocarcinogenesis.

Flow cytometric analysis of neoplastic nodules and hepatocellular carcinomas induced by ciprofibrate in the rat

Alterations in DNA ploidy accompany hepatocellular carcinoma (HCC). However, changes in DNA content are also seen in regenerating liver and with increasing age. Thus, to investigate the role of DNA ploidy changes in development of HCC, flow cytometric DNA content determinations were done in a rat model system of peroxisome proliferator-induced HCC. Paraffin blocks of liver isolated from 18 Fisher 344 male rats fed ciprofibrate for 20 weeks (4), 40 weeks (4) or 20 months (10) were examined. Livers from age-matched control rats were also examined. From the 20 month ciprofibrate group, nine neoplastic nodules (NNs), 27 HCCs and four non-tumorous surrounding tissue controls (NTCs) were examined. Significant DNA tetraploid populations were seen in both the NNs and NTCs. A significant increase in the percentage of DNA diploid cells was observed in the NN samples. No significant difference in the percentage S-phase cells was seen. Emergence of cell populations with new DNA ploidy classes (8c or DNA aneuploid) as compared with NTCs was only seen in HCCs (7 of 27), and five of these seven were DNA aneuploid, as distinct from DNA tetraploid, populations. A total of 16 of 24 HCC samples that were adequate for cell cycle analysis had average percent S-phase greater than the mean of the NTCs plus three standard deviations. Although a direct role cannot be inferred, these results support the hypothesis that increases in the fraction of diploid cells is an important early event in the development of rat HCC and that further alterations in DNA ploidy and increased proliferative fraction accompany the development of HCC.

The pathophysiology of angiogenesis

The formation of new capillary blood vessels, a process termed "angiogenesis", is one of the most pervasive and fundamentally essential biological processes encountered in mammalian organizations. Angiogenesis is an important event in a variety of physiological settings, such as embryonic development, chronic inflammation, and wound repair. It is a process that is tightly regulated in both time and space. Angiogenesis is driven by a cocktail of growth factors and pro-angiogenic cytokines and is tempered by an equally diverse group of inhibitors of neovascularization. Angiogenesis is also central to the etiology and pathogenesis of a number of pathological processes that include, among others, solid tumors, diseases of the eye, and chronic inflammatory disorders such as rheumatoid arthritis, psoriasis, and periodontitis. Based on recent work from several laboratories, it is now eminently clear that most if not all angiogenesis and vasoproliferative-dependent disease processes are not only a consequence of the unrestricted production of normal or aberrant forms of pro-angiogenic mediators but also the result of a relative deficiency in angiogenic-inhibitory molecules. In this review, I will describe how these multifunctional mediator systems function to coordinate and regulate the angiogenic response, and how disruption in the molecular controls that regulate the production of pro-angiogenic and angiostatic mediators leads to aberrant angiogenesis and disease. The implications of these findings in the development of novel therapeutic strategies for the treatment of diseases characterized by disregulated angiogenesis will also be discussed.

The genetic basis of colorectal cancer--clinical implications

Colorectal carcinomas demonstrate extensive molecular genetic alterations throughout the genome. The genetic changes in cancer of the colon and rectum are among the best understood of any common human cancer. The genetic abnormalities include both dominant-acting oncogenes (Ki-ras, c-src) and tumor-suppressor genes which undergo inactivation or loss (APC, DCC, p53). The evolution of the cancer is a complicated and multistep process. At the various steps of this phenomenon we can recognize specific molecular genetic alterations. These particular genetic changes may be useful as improved markers to predict those patients who have an aggressive cancer of the colon, with occult metastases or increased metastatic capability and this selection of patients could lead to improved surgical and medical management.

Increasing multiple myeloma mortality among the elderly: a manifestation of aging and differential survival

Increasing multiple myeloma incidence and mortality among the elderly in industrialized nations has been attributed to associated environmental carcinogens. Age-specific multiple myeloma mortality rates in the United States from 1968 to 1989 were analyzed using the Strehler-Mildvan modification of the Gompertz relationship between aging and mortality. The results suggest that worsening environmental influences are not responsible for increasing multiple myeloma mortality among the elderly. Differential survival, a concept originally popularized by Charles Darwin, and its effect upon the surviving gene pool in an aging population is an alternative explanation for increasing multiple myeloma incidence and mortality in the elderly.

Detection of TP53 gene mutations in human sarcomas

To determine the frequency and type of TP53 mutations in human sarcomas, we examined exons 5-8 of the TP53 gene in 48 sarcomas using single-strand conformation polymorphism (SSCP) analysis and direct sequencing. Nine tumours had mobility-shifts on SSCP analysis, and sequencing of six of these tumours revealed 10 mutations: one insertion, two deletions and seven point mutations (four transitions and three transversions). Four of these mutations resulted in frame-shifts, one in a truncated protein, four cases in mono-allelic point mutations and one case in an altered splice site. These data show that approximately 20% of sarcomas harbour TP53 gene alterations and illustrate a variety of TP53 gene mutation types.

Molecular evidence that childhood monosomy 7 syndrome is distinct from juvenile chronic myelogenous leukemia and other childhood myeloproliferative disorders

The observation that juvenile chronic myelogenous leukemia (JCML) and childhood bone marrow monosomy 7 syndrome (Mo 7) are similar in many clinical and epidemiologic respects suggests a shared pathogenic basis and raises the possibility that the bone marrows of patients with JCML might lose chromosome 7 alleles by mechanisms that do not result in detectable cytogenetic deletions. We used a series of polymorphic markers mapped to chromosome 7 to test this hypothesis in 22 children with MPS and MDS, including 19 with JCML. All MPS and MDS samples demonstrated allelic heterozygosity with at least one chromosome 7 marker; 16 were heterozygous with probes from both 7p and 7q. Furthermore, the percentage of patient bone marrow samples heterozygous at each locus tested was similar to the frequency observed in the normal population. Whereas these data demonstrate that submicroscopic loss of large segments of chromosome 7 alleles is uncommon in children with MPS and MDS who do not have Mo 7, they do not exclude small deletions around an uncharacterized tumor-suppressor locus. Our results suggest that a number of distinct molecular events contribute to leukemogenesis, and we propose a multistep model to explain the similarities and differences between the major subtypes of childhood MPS and MDS.

Assessment of cytogenetic changes in human populations at risk in Egypt

Humans are exposed to numerous environmental agents that can increase the probability of mutagenicity and carcinogenicity. Most of environmental exposures involve concurrent or sequential exposure to several agents in air, water, and food. Interactive effects in carcinogenesis have been described for a certain number of combinations of agents. They are described in terms of enhancement or inhibition of carcinogenesis. Risk assessment of exposure to environmental agents can start either from laboratory studies after exposure to different agents or from epidemiological studies in relation to actual exposure. The use of genotoxicity testing is essential for assessment of potential human toxicity so that hazards can be prevented. Cytogenetic monitoring of human populations exposed to environmental agents has proved to be a useful tool for detecting their mutagenic effects. Cytogenetic analysis of human chromosomes in peripheral lymphocytes allows direct detection of mutation in somatic cells. Various methods can be used for chromosomal analysis (conventional chromosomal analysis, sister chromatid exchange, micronucleus frequency detection). Micronucleus frequency can be detected either in peripheral blood lymphocytes or in exfoliated cells. Different examples of human population studies are presented in this review. Several problems which are found in biomonitoring studies are discussed.

Identification of a cell-surface glycoprotein associated with normal mammary and extramammary epithelial cells

The goal of the study was to identify any normal genes that may become inactivated in malignant cells, with associated modifications or loss of gene products. Consequently, attempts were made to identify such products by generating monoclonal antibodies using an immune tolerisation-immunisation procedure. Using such a technique, a plasma membrane-associated glycoprotein with an apparent molecular weight of 92 kDa was identified. The glycoprotein was termed luminal epithelial antigen (LEA.92). The pattern of expression of LEA.92 was demonstrated by an indirect immunostaining technique. Using an in vitro model system representing various stages of breast oncogenesis, LEA.92 was detected on normal or immortalised mammary epithelial cell (MEC) lines which were dependent on epidermal growth factor (EGF) and anchorage formation for growth and non-tumorigenic in nude mice. In contrast, LEA.92 was undetectable on oncogenically transformed or established lines of mammary carcinoma cell lines which were independent of EGF or anchorage formation for growth and were highly tumorigenic. The results appear to suggest a correlation between the down-regulation of LEA.92 and the development of tumorigenicity in malignant MEC lines. Furthermore, the patterns of expression of LEA.92 on breast cells in tissue mirrored those of breast epithelial cells in cell cultures. LEA.92 was detected on the surface of normal but not malignant epithelial cells, which included breast, cervix, colon, lung, pancreas and stomach. LEA.92 appeared to be distinct from receptor for epidermal growth factor, antigens associated with milk fat globule membrane and the family of epithelium-specific keratins.

T-cell based cancer immunotherapy: direct or redirected tumor-cell recognition?

In development of strategies for immunotherapy of cancer a new emphasis is emerging, termed T-cell retargeting, which involves artificial redirection of cytotoxic T lymphocytes (CTL) against cancer cells, using bispecific reagents. In this article, Gideon Beun, Cornelis van de Velde and Gert Jan Fleuren evaluate this potential strategy for cellular immunotherapy, and propose how the gap between in vitro results and clinical application might be bridged.

Aging, genomic entropy and carcinogenesis: implications derived from longitudinal age-specific colon cancer mortality rate dynamics

Many types of cancer are intrinsically linked to the process of aging. Aging, from the perspective of the second law of thermodynamics, can be viewed as associated with the inevitable and natural increase in informational entropy of the genome. The molecular biologic basis of increasing genetic informational entropy is the inherent and variable instability of different regions of genome. Colon cancer cells have been shown to have characteristic acquired genetic abnormalities, most commonly, deletions in presumed tumor suppressor genes. Age-specific colon cancer mortality rates in the US from 1958 to 1988 were subjected to longitudinal Gompertzian analysis, a method that may identify and distinguish among genetic, environmental and competitive influences upon mortality. The Strehler-Mildvan modification of the Gompertz relationship between aging and mortality can be used to determine a relative measure of the rate of increase in informational entropy (a reflection of genetic instability) for those genetic factors that are involved in the pathogenesis of colon cancer.

Simultaneous presentation of symptomatic subependymomas in siblings: case reports and review

Two young adult siblings independently developed similar neurological complaints that included headaches, photophobia, nausea, and intermittent lancinating facial pains. Magnetic resonance imaging revealed fourth ventricular lesions that required surgery in both patients. A pathological review revealed subependymomas with virtually identical histological features. The clinical features and common pathological findings of both patients suggest that familial subependymomas may have a maldevelopmental origin with genetic implications.

Genotypic classification of colorectal adenocarcinoma. Biologic behavior correlates with K-ras-2 mutation type

BACKGROUND

New measures enabling better prediction of biologic behavior of large bowel cancer are highly desirable. One hundred ninety-four consecutive primary, recurrent, and metastatic colorectal adenocarcinomas, accessioned during 1991 at Rhode Island Hospital, were classified according to the presence and specific type of K-ras-2 point mutation.

METHODS

An integrated histopathologic-genetic approach was used to detect mutations starting with minute, topographically selected, tissue samples from formaldehyde-fixed, paraffin-embedded specimens.

RESULTS

Each colorectal adenocarcinoma exhibited either no or only one of seven specific types of K-ras-2 mutation. The mutation type of each primary tumor was present consistently in its metastatic deposits. Thirty-five percent of primary colorectal adenocarcinomas were found to be mutated (42 of 119). A significantly higher mutation rate (65%) was seen in lymphogenous-hematogenous metastases as a group (35 of 54; P < 0.005). By contrast, 22% of anastomotic recurrences and transcoelomic metastasis were mutated (4 of 18). Twenty-eight percent of adenocarcinomas with invasion limited to muscularis propria (Tis, T1, T2) were mutated (16 of 57), compared to 41% for more deeply invasive tumors (T3, T4; 26 of 63). When colorectal adenocarcinomas were analyzed by specific K-ras-2 mutation type, it was found that codon 13 mutated tumors did not progress to local or distant metastasis (P < 0.01). Tumors having a codon 12 valine substitution did not metastasize beyond pericolonic-perirectal lymph nodes. In contrast, colorectal cancers with codon 12 aspartic acid substitutions accounted for most of the distant hematogenous deposits (P < 0.01). Tumors with normal K-ras-2 accounted for most intraperitoneal deposits.

CONCLUSIONS

Genotyping of colorectal adenocarcinoma by K-ras-2 status can identify subsets of patients likely to pursue indolent and aggressive forms of disease. The integrated histopathologic-genetic approach outlined is feasible for use in diagnostic pathology, providing information that together with clinicopathologic staging may individualize and optimize treatment.

Association of somatotrophinomas with loss of alleles on chromosome 11 and with gsp mutations

The molecular pathology of somatotrophinomas has been investigated by a combined search for dominant mutations of the gene encoding the Gs alpha protein and for recessive mutations involving chromosome 11q13, which contains the gene causing multiple endocrine neoplasia type 1 (MEN1). Somatotrophinomas and peripheral leukocytes were obtained from thirteen patients with acromegaly; one patient also suffered from MEN1. Five DNA probes identifying restriction fragment length polymorphisms from 11q revealed allele loss in pituitary tumors from five (four non-MEN1 and one MEN1) patients. Deletion mapping revealed that the region of allele loss common to the somatotrophinomas involved 11q13. An analysis for similar allelic deletions at 12 other loci from chromosomes 1-5, 7-9, 12-14, and 17 did not reveal generalized allele loss in the somatotrophinomas. These results, which represent the first report of chromosome 11 allele loss occurring in non-MEN1 somatotrophinomas, indicate that a recessive oncogene on 11q13 is specifically involved in the monoclonal development of somatotrophinomas. In addition Gs alpha mutations were detected in two non-MEN1 somatotrophinomas, one of which also revealed allele loss of chromosome 11. Thus, our results reveal that the development of somatotrophinomas is associated with alterations in both dominant and recessive oncogenes and further characterization of these genetic abnormalities will help to elucidate the multistep etiology and progression of somatotrophinomas.