Somatic activation of rasK gene in a human ovarian carcinoma

Early-Life Exposure to Lipopolysaccharide Induces Persistent Changes in Gene Expression Profiles in the Liver and Spleen of Female FVB/N Mice

The objective of this study was to investigate how subcutaneous (sc) lipopolysaccharide (LPS) administration affects the gene expression profiles of insulin signaling as well as innate and adaptive immunity genes in mouse livers and spleens. FVB/N female mice were randomly assigned to one of two treatment groups at 5 weeks of age: (1) a six-week subcutaneous injection of saline at 11 μL/h (control-CON), or (2) a six-week subcutaneous injection of LPS from Escherichia coli 0111:B4 at 0.1 μg/g body weight at 11 μL/h. At 106 weeks (i.e., 742 days) after the last treatment, mice were euthanized. Following euthanasia, liver and spleen samples were collected, snap frozen, and stored at -80 °C until gene expression profiling. LPS upregulated nine genes in the liver, according to the findings (Pparg, Frs3, Kras, Raf1, Gsk3b, Rras2, Hk2, Pik3r2, and Myd88). With a 4.18-fold increase over the CON group, Pparg was the most up-regulated gene in the liver. Based on the annotation cluster analysis, LPS treatment upregulated liver genes which are involved in pathways associated with hepatic steatosis, B- and T-cell receptor signaling, chemokine signaling, as well as other types of cancers such as endometrial cancer, prostate cancer, and colorectal cancer. LPS increased the spleen expression of Ccl11, Ccl25, Il6, Cxcl5, Pparg, Tlr4, Nos2, Cxcl11, Il1a, Ccl17, and Fcgr3, all of which are involved in innate and adaptive immune responses and the regulation of cytokine production. Furthermore, functional analysis revealed that cytokine-cytokine receptor interaction and chemokine signaling pathways were the most enriched in LPS-treated mice spleen tissue. Our findings support the notion that early-life LPS exposure can result in long-term changes in gene expression profiling in the liver and spleen tissues of FVB/N female mice.

The path to the clinic: a comprehensive review on direct KRASG12C inhibitors

The RAS oncogene is both the most frequently mutated oncogene in human cancer and the first confirmed human oncogene to be discovered in 1982. After decades of research, in 2013, the Shokat lab achieved a seminal breakthrough by showing that the activated KRAS isozyme caused by the G12C mutation in the KRAS gene can be directly inhibited via a newly unearthed switch II pocket. Building upon this groundbreaking discovery, sotorasib (AMG510) obtained approval by the United States Food and Drug Administration in 2021 to become the first therapy to directly target the KRAS oncoprotein in any KRAS-mutant cancers, particularly those harboring the KRASG12C mutation. Adagrasib (MRTX849) and other direct KRASG12C inhibitors are currently being investigated in multiple clinical trials. In this review, we delve into the path leading to the development of this novel KRAS inhibitor, starting with the discovery, structure, and function of the RAS family of oncoproteins. We then examine the clinical relevance of KRAS, especially the KRASG12C mutation in human cancer, by providing an in-depth analysis of its cancer epidemiology. Finally, we review the preclinical evidence that supported the initial development of the direct KRASG12C inhibitors and summarize the ongoing clinical trials of all direct KRASG12C inhibitors.

40 Years of RAS-A Historic Overview

It has been over forty years since the isolation of the first human oncogene (HRAS), a crucial milestone in cancer research made possible through the combined efforts of a few selected research groups at the beginning of the 1980s. Those initial discoveries led to a quantitative leap in our understanding of cancer biology and set up the onset of the field of molecular oncology. The following four decades of RAS research have produced a huge pool of new knowledge about the RAS family of small GTPases, including how they regulate signaling pathways controlling many cellular physiological processes, or how oncogenic mutations trigger pathological conditions, including developmental syndromes or many cancer types. However, despite the extensive body of available basic knowledge, specific effective treatments for RAS-driven cancers are still lacking. Hopefully, recent advances involving the discovery of novel pockets on the RAS surface as well as highly specific small-molecule inhibitors able to block its interaction with effectors and/or activators may lead to the development of new, effective treatments for cancer. This review intends to provide a quick, summarized historical overview of the main milestones in RAS research spanning from the initial discovery of the viral RAS oncogenes in rodent tumors to the latest attempts at targeting RAS oncogenes in various human cancers.

MicroRNA-Based Therapeutic Strategies for Targeting Mutant and Wild Type RAS in Cancer

MicroRNAs (miRs) have been causally implicated in the progression and development of a wide variety of cancers. miRs modulate the activity of key cell signaling networks by regulating the translation of pathway component proteins. Thus, the pharmacological targeting of miRs that regulate cancer cell signaling networks, either by promoting (using miR-supplementation) or by suppressing (using antisense oligonucleotide-based strategies) miR activity is an area of intense research. The RAS-extracellular signal regulated kinase (ERK) pathway represents a major miR-regulated signaling network that endows cells with some of the classical hallmarks of cancer, and is often inappropriately activated in malignancies by somatic genetic alteration through point mutation or alteration of gene copy number. In addition, recent progress indicates that many tumors may be deficient in GTPase activating proteins (GAPs) due to the collaborative action of oncogenic miRs. Recent studies also suggest that in tumors harboring a mutant RAS allele there is a critical role for wild type RAS proteins in determining overall RAS-ERK pathway activity. Together, these two advances comprise a new opportunity for therapeutic intervention. In this review, we evaluate miR-based therapeutic strategies for modulating RAS-ERK signaling in cancers; in particular for more direct modulation of RAS-GTP levels, with the potential to complement current strategies to yield more durable treatment responses. To this end, we discuss the potential for miR-based therapies focused on three prominent miRs including the pan-RAS regulator let-7 and the GAP regulator comprised of miR-206 and miR-21 (miR-206/21).

Ras history: The saga continues

Although the roots of Ras sprouted from the rich history of retrovirus research, it was the discovery of mutationally activated RAS genes in human cancer in 1982 that stimulated an intensive research effort to understand Ras protein structure, biochemistry and biology. While the ultimate goal has been developing anti-Ras drugs for cancer treatment, discoveries from Ras have laid the foundation for three broad areas of science. First, they focused studies on the origins of cancer to the molecular level, with the subsequent discovery of genes mutated in cancer that now number in the thousands. Second, elucidation of the biochemical mechanisms by which Ras facilitates signal transduction established many of our fundamental concepts of how a normal cell orchestrates responses to extracellular cues. Third, Ras proteins are also founding members of a large superfamily of small GTPases that regulate all key cellular processes and established the versatile role of small GTP-binding proteins in biology. We highlight some of the key findings of the last 28 years.

An Update on the Biology of RAS/RAF Mutations in Colorectal Cancer

Deaths caused by colorectal cancer (CRC) are among the leading causes of cancer-related death in the United States and around the world. Approximately 150,000 Americans are diagnosed with CRC each year and around 50,000 will die from it. Mutations in many key genes have been identified that are important to the pathogenesis of CRC. Among the genes mutated in CRC, RAS and RAF mutations are common events. Both RAS and RAF are critical mediators of the mitogen-activated protein kinase (MAPK) pathway that is involved in regulating cellular homeostasis, including proliferation, survival, and differentiation. In this review, we provide a historical perspective and update on RAS/RAF mutations as related to colorectal cancer. Additionally, we will review recent mouse models of RAS and RAF mutations that have an impact on CRC research.

Molecular aspects of ovarian cancer

Ovarian cancer is caused by genetic alterations that disrupt proliferation, apoptosis, senescence and DNA repair. Approximately 10% of ovarian cancers arise in women who have inherited mutations in cancer susceptibility genes (BRCA1 or BRCA2). The ability to perform genetic testing allows identification of women at increased risk who can be offered prophylactic oophorectomy or other interventions aimed at preventing ovarian cancer. The vast majority of ovarian cancers are sporadic, resulting from the accumulation of genetic damage over a lifetime. Several specific genes involved in ovarian carcinogenesis have been identified, including the p53 tumour suppressor gene and HER2/ neu andPIC3KA oncogenes. The recent availability of expression microarrays has facilitated the simultaneous examination of thousands of genes, and this promises to extend further our understanding of the molecular events involved in the development of ovarian cancers. Hopefully, this knowledge can be translated into effective screening, treatment, surveillance, and prevention strategies in the future.

ras gene activation and infrequent mutation in papillary serous carcinoma of the peritoneum

OBJECTIVE

The ras genes are a well-studied family of proto-oncogenes whose involvement in many cancers has been delineated. However, K-ras mutations have not previously been examined in papillary serous carcinoma of the peritoneum (PSCP), a tumor which resembles serous epithelial ovarian carcinoma (SEOC) both in histology and epidemiology. In this study we examine the role of the K-ras oncogene in PSCP compared to SEOC.

METHODS

Using single-strand conformational polymorphism analysis and cycle sequencing protocols, we evaluated our collection of 51 cases of PSCP for K-ras mutations and compared these findings with the experience in SEOC. We then examined 5 cases of PSCP for activation of ras proteins and MAP kinase to evaluate the potential involvement of the ras pathway in PSCP tumorigenesis.

RESULTS

We found only one K-ras mutation in our 51 cases (2%) of PSCP compared to three mutations in 46 cases (6.5%) of high-grade, late-stage SEOC. This was not significantly different (P > 0.10). In the single PSCP case with a K-ras mutation, the mutation was found in only one of five tumor sites tested. All four mutations involved a single nucleotide alteration in codon 12 (GGT to GTT, Gly to Val). To evaluate the ras pathway in PSCP, we used the known activated ras binding domain on Raf-1 to perform an assay to test for activated ras. We identified ras activation in 4 of 5 PSCP cases tested and, to confirm that the activation was functional, we tested and found similar activation of MAP kinase, a downstream mediator for K-ras expression.

CONCLUSIONS

K-ras mutations occur at low rates in both PSCP and high-grade, late-stage SEOC, and therefore K-ras mutations are not involved in the development of these two diseases. Finding the mutation in only one of multiple tumor sites in the PSCP case supports growing evidence for a multifocal origin of PSCP. Our findings of ras activation in four of five cases of PSCP suggest that ras activation by mechanisms other than genetic mutation is important for PSCP tumorigenesis.

Molecular aspects of ovarian cancer. Is gene therapy the solution?

Genetic abnormalities of cancer cells are complex and usually nonspecific. Genetic anomalies specific to ovarian cancer have not been reported. This article focuses on what molecular anomalies are known in ovarian cancer and describes the first trials that have used transfer of genes to reestablish a normal cellular function in this disease. Suicide gene therapy has been the prototype of this new therapeutic approach.

Isolation and characterization of mouse ovarian surface epithelial cell lines

The incidence of ovarian malignancies has significantly increased in the past decades in many countries, however, an appropriate animal model system enabling the study of ovarian cancer such as stable mouse ovarian epithelial cell lines has not yet been developed. Here we report the establishment of cell lines derived from mouse ovarian surface epithelium (MOSE) by two procedures--one, through the introduction of SV40 large T antigen DNA into C3H/He MOSE (T-Ag-MOSE) and another through spontaneous immortalization of cells from p53-deficient MOSE (p53-def-MOSE). p53-def-MOSE cell line did not show any transformed phenotype either in vitro culture system nor in vivo tumorigenicity assay, whereas T-Ag-MOSE formed tumors in nude mice. Tumors formed by the injection of T-Ag-MOSE were undifferentiated malignancies associated with heterologous mesothelial tissues such as those of the osteoid phenotype. The established MOSE cell lines are useful in the molecular analysis of the multistep carcinogenesis of ovarian tissues in humans.

The genetics of ovarian cancer: molecular biology and clinical application

Ovarian cancer is the fifth most common malignancy among American women and the fourth leading cause of cancer death. The rapid advances in molecular genetic analysis, presymptomatic detection, and treatment of ovarian cancer are staggering. In this review, both the genetic component and the molecular biology of ovarian cancer are discussed, as well as current recommendations for genetic counseling. It is important for the practicing obstetrician and gynecologist to become familiar with these concepts, for it is he or she who will likely serve as a primary resource of information for these patients.

Human ovarian cancer of the surface epithelium

Epidemiologic studies have shown that the risk of cancer in the ovarian surface epithelium is decreased by factors that suppress ovulation, whereas uninterrupted ovulation has been associated with increased risk. This suggests that ovulation may play a critical role in ovarian carcinogenesis. More recently, molecular studies have demonstrated alterations in specific oncogenes and tumor suppressor genes in ovarian cancers. Overexpression of the HER-2/neu oncogene occurs in approximately 30% of ovarian cancers and correlates with poor survival. Although mutation of the K-ras oncogene has been found in some mucinous ovarian cancers, mutations in this gene appear to be more common in borderline ovarian tumors. Amplification of c-myc occurs in approximately 30% of ovarian cancers and is more frequently seen in serous cancers. Mutation of the p53 tumor suppressor gene, with resultant overexpression of mutant p53 protein, occurs in 50% of stage III/IV and 15% of stage I/II ovarian cancers. Most p53 mutations in ovarian cancers are transitions, which suggests that they arise spontaneously rather than due to exogenous carcinogens. In contrast to the acquired genetic alterations described above that are a feature of sporadic ovarian cancers, 5-10% of ovarian cancers probably arise due to inherited genetic defects. Recently, the BRCA1 tumor suppressor gene has heen identified and shown to be responsible for most cases of hereditary ovarian cancer. Further studies are needed to augment our understanding of the molecular pathogenesis of ovarian cancer.

Analysis of the Rb gene and cyclin-dependent kinase 4 inhibitor genes (p16INK4 and p15INK4B) in human ovarian carcinoma cell lines

In the present study, we analyzed human ovarian carcinoma cell lines for abnormalities in the tumor suppressor gene Rb (retinoblastoma) and in cyclin-dependent kinase 4 (CDK4) inhibitor genes (p16INK4 and p15INK4B) using molecular biology techniques. For the Rb gene, in all six cell lines (PA-1, Caov-3 and -4, OVCAR-3, SK-OV-3, and Kuramochi), Rb gene abnormality was not detected using Southern blotting. In the Caov-3 cell line transcripts were not detectable by either Northern blot or polymerase chain reaction. Sequence analysis of the entire coding region of the Rb gene revealed point mutations (AAC to GAC) resulting in codon 123 (Asn to Asp) changes in the Caov-4 cell line. In the PA-1 cell line both wild-type Rb and mutant-type Rb (codon 798: CGG to TGG) were expressed, and in the OVCAR-3 cell line both wild-type Rb and mutant-type Rb (codon 704: ATG to GTG) were expressed. In four of six human ovarian carcinoma cell lines Rb gene abnormality was detected. For the p16INK4 and p15INK4B genes, only the SK-OV-3 cell line had abnormalities. There was a gene rearrangement or minor deletion of the p16INK4 gene in the SK-OV-3 cell line, while the p15INK4B gene was deleted in this cell line. In the SK-OV-3 cell line no mRNAs of p16INK4 and p15INK4B were expressed. At the point of Rb gene inactivation, we can explain five cell lines of six: four cell lines had abnormalities in the Rb gene itself, which is another mechanism by which the Rb gene is inactivated, while one cell line (SK-OV-3) had abnormalities in CDK4 inhibitor genes, another of the inactivation mechanisms of the Rb gene. These data suggest that abnormalities of Rb and CDK4 inhibitor genes (p16INK4, p15INK4B) may be involved in human ovarian carcinogenesis.

Expression of cyclin D1 and c-Ki-ras gene product in human epithelial ovarian tumors

The expression of cyclin D1 gene product in human ovarian tumors was studied. We found that cyclin D1 is expressed at high levels in several ovarian cancer cell lines. Immunohistochemical study also showed that a significant proportion of primary ovarian tumor tissues overexpressed cyclin D1 gene product. Clear nuclear staining of cyclin D1 protein was detected in 28% of the cases. We also characterized the expression of c-Ki-ras gene product in ovarian cancer cell lines and tumor tissues. Amplification or overexpression of this proto-oncogene has been reported in ovarian tumors from Taiwan. These results show that c-Ki-ras is strongly expressed in PA-1 and NIH:OVCAR-3 cells in which cyclin D1 also expressed at high levels. Specific cytoplasmic staining of c-Ki-ras protein was detected in 11 tumors (52%). Statistical analyses show a strong positive correlation between cyclin D1 and c-Ki-ras immunoexpression. Thus, these data support the ideas that cyclin D1 may be involved in the pathogenesis of ovarian cancer, and coactivation of cyclin D1 and c-Ki-ras gene expression may represent one of the major pathways that lead to the development of ovarian cancer in Taiwan.

Pathogenesis of ovarian cancers

OBJECTIVE

To review our current understanding of the molecular genetic events involved in the development of epithelial ovarian cancers.

METHODS

Molecular biologic techniques have been used to examine the role of growth-stimulatory genes (oncogenes) and -inhibitory genes (tumor suppressors) in ovarian cancer.

RESULTS

A number of different peptide growth factors and their receptors are expressed by normal and malignant ovarian epithelial cells. However, the role, if any, of growth factors in ovarian carcinogenesis or maintenance of the transformed phenotype remains unknown. Amplification and overexpression of the HER-2/neu and c-myc oncogenes occur in a significant fraction of epithelial ovarian cancers (20-30%). Overexpression of HER-2/neu has correlated with poor survival in some studies, whereas c-myc amplification is more common in serous cancers. Mutation of the K-ras oncogene frequently occurs in borderline ovarian tumors, but is less common in invasive epithelial ovarian cancers. Mutation of the p53 tumor suppressor gene occurs in approximately half of advanced (stage III/IV) ovarian cancers and in 15% of early (stage IA/IB) cases. Most recently, preliminary studies have focused on the role of other tumor suppressor genes, cyclins, WAF1, and DNA mismatch repair genes.

CONCLUSIONS

An understanding of the molecular events involved in the pathogenesis of epithelial ovarian cancer is beginning to evolve. Improvements in early diagnosis, treatment, and prevention of this deadly disease are dependent on further progress in this area.

Point mutation of the ras oncogene in human ovarian cancer

The ras oncogene exists in a variety of human cancers, including carcinomas of bladder, breast, colon, kidney, liver, lung, ovary, pancreas, and stomach. The ras genes acquire transforming activity either by enhanced expression or by a single point mutation. A single base-pair mutation at specific sites within ras genes endows them with the capacity to transform certain cell lines in vitro. In this study, we showed the patterns of point mutations in codons 12, 13, and 61 of ras genes in human ovarian cancer. The experimental procedures were isolation of genomic DNA from normal ovary and ovarian cancer tissue specimens, amplification of a genomic DNA segment (about 100 bp) using different 5' and 3' extension primers in the polymerase chain reaction (PCR), labeling and purification of synthetic mutation-specific oligonucleotide probes, slot-blot hybridization, and autoradiography. The three reaction steps for the PCR cycle were: 96 degrees C for 1 min in step 1, 56 degrees C for 1 min in step 2, and 74 degrees C for 1 min in step 3. The PCR reaction was repeated totally for 30 cycles. In 28 tissue specimens of human ovarian cancer examined, one specimen was found with a c-Ha-ras point mutation at codon 12, two had a c-Ki-ras mutation at codon 12, and one had a c-Ki-ras mutation at codon 13.

Genetics, natural history, tumor spectrum, and pathology of hereditary nonpolyposis colorectal cancer: an updated review

Hereditary nonpolyposis colorectal cancer (HNPCC) dates to Warthin's description of family G, which he began studying in 1895. Warthin's observations were not fully appreciated until 1966 when two families with an autosomal dominant inheritance pattern of nonpolyposis colorectal cancer (CRC) and endometrial cancer were described. This condition was first termed the "cancer family syndrome" and was later renamed HNPCC. Some have proposed that HNPCC consists of at least two syndromes: Lynch syndrome I, with hereditary predisposition for CRC having early (approximately 44 years) age of onset, a proclivity (70%) for the proximal colon, and an excess of synchronous and metachronous colonic cancers and Lynch syndrome II, featuring a similar colonic phenotype accompanied by a high risk for carcinoma of the endometrium. Transitional cell carcinoma of the ureter and renal pelvis and carcinomas of the stomach, small bowel, ovary, and pancreas also afflict some families. Current estimates indicate that HNPCC may account for as much as 6% of the total CRC burden. There are no known premonitory phenotypic signs or biomarkers of cancer susceptibility in the Lynch syndromes. This report will summarize current knowledge, with emphasis on the manner in which this knowledge can be employed effectively for diagnosis and management of HNPCC.

Cell growth regulation in epithelial ovarian cancer

BACKGROUND

As in the case of other epithelial neoplasms, most ovarian cancers arise from single clones of cells that have undergone multiple genetic alterations. A comparison of normal and malignant ovarian epithelium has identified several differences in growth regulation by peptide growth factors, protooncogenes, and tumor suppressor genes.

METHODS

Recent articles and abstracts have been reviewed.

RESULTS

The malignant ovarian epithelial phenotype has been associated with (1) autocrine growth stimulation by transforming growth factor-alpha, (2) loss of autocrine growth inhibition by transforming growth factor-beta, (3) mutation or amplification of ras in 2-12% of cases, (4) amplification of myc in 23% of specimens, (5) expression of fms in 56% of cases with potential autocrine stimulation by macrophage colony stimulating factor, (6) paracrine stimulation by macrophage products including interleukin-1, interleukin-6 and tumor necrosis factor, (7) overexpression of c-erbB-2 (HER-2/neu) in 30% of cases, and (8) mutation with consequent overexpression of p53 in 50% of advanced ovarian cancers. A poor clinical prognosis is associated with expression or overexpression of the epidermal growth factor receptor, fms, and HER-2/neu. Antibodies against the extracellular domain of the HER-2/neu gene product p185 inhibit the growth of tumor cells that overexpress HER-2/neu and are associated with marked decreases in diacylglycerol levels. The intracellular kinase domain is required for growth inhibition. Antibodies that inhibit growth stimulate phosphorylation of intracellular substrates. Ricin A chain monoclonal antibody conjugates that react with p185 also inhibit the growth of tumor cells that overexpress p185. The intracellular kinase region is not required for immunotoxin-mediated killing. Coexpression of HER-2/neu and the epidermal growth factor receptor has been observed in 65% of epithelial ovarian cancers and in a limited number of normal tissue from a fraction of donors.

CONCLUSIONS

Multiple alterations in growth factors, protooncogenes and growth factors have been detected in different epithelial ovarian cancers. Inappropriate signalling from receptor tyrosine kinases may be particularly important for ovarian oncogenesis. Drugs that affect tyrosine kinase and phosphatase activity deserve attention as potential therapeutic agents for ovarian cancer. The extracellular domains of the HER-2/neu gene product p185 and the epidermal growth factor receptor may provide useful targets for serotherapy.

Genetic epidemiology of epithelial ovarian cancer

BACKGROUND

Aside from age, family history is the strongest predictor of ovarian cancer risk. Genetic components of risk for ovarian cancer have been evaluated by a number of designs, including case-control studies of family history and other risk factors, segregation and genetic linkage studies, and studies of biomarkers and tumor-specific cytogenetic abnormalities.

METHODS

Data were extracted from all available case-control studies that included family history. Cytogenetic, biomarker, segregation, analytic, and genetic linkage studies were reviewed.

RESULTS

Family history of ovarian cancer confers a 3.6-fold increased risk for this disease. Segregation studies of breast and ovarian cancer in five large families were consistent with dominant inheritance. Low levels of alpha-L-fucosidase confer mildly increased risk for ovarian cancer. Low galactose-1-phosphate uridyl transferase and type A blood group may increase risk for ovarian cancer. Cytogenetic and oncogene studies have identified regions that may be important in tumorigenesis and metastasis, but discriminating between early and late changes is difficult from these studies. Presence of a genetic susceptibility locus for breast and ovarian cancer has been confirmed on chromosome 17q21.

CONCLUSIONS

Family history is an important predictor of ovarian cancer risk. In rare families, a specific dominantly acting gene can be identified, but in the vast majority of familial ovarian cancers the underlying mechanism remains unclear. Specific studies are needed for women with a family history of ovarian cancer because evidence suggests modification of the effects of oral contraceptive use and reproductive patterns in this population of women.

Growth regulation and transformation of ovarian epithelium

The discovery of peptide growth factors and cancer-causing genes (oncogenes and tumor-suppressor genes) has provided us with the exciting opportunity to begin to understand the molecular pathology of human ovarian cancer. Activation of several genes, including HER-2/neu, myc, ras, and p53 have been described in some ovarian cancers. In addition, some protooncogenes such as the epidermal growth factor receptor (erbB) and the M-CSF receptor (fms) are expressed along with the respective ligands (peptide growth factors) in some ovarian cancers. Although the studies reviewed in this paper represent a promising beginning, we remain far from a comprehensive understanding of growth regulation and transformation of human ovarian epithelium.

Association of ras p21 with differentiation of epidermal keratinocytes in proliferating skin diseases

We examined the localization of DNA replicating cells and ras oncogene product p21 positive cells in proliferating skin diseases, such as psoriasis vulgaris, lichen planus, verruca vulgaris, verruca plana juvenilis and seborrheic keratosis. ras p21-positive cells were found rather in the differentiated layers than in the proliferating layers of the epidermis. We indicate that the expression of ras p21 can be associated with the differentiation of epidermal keratinocytes not only in tumor tissues but also in inflammatory skin disease.

Synergism between a novel amphibian oocyte ribonuclease and lovastatin in inducing cytostatic and cytotoxic effects in human lung and pancreatic carcinoma cell lines

A novel anti-tumour amphibian oocyte RNase, ONCONASER (ONC), previously known as P-30 Protein, is in the clinical trials. The effect of ONC alone and in combination with lovastatin (LVT), an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, a rate-limiting enzyme of mevalonate (MVA) and cholesterol synthesis pathway, in three human tumour cell lines ASPC-1 pancreatic, A-549 lung, and HT-520 lung carcinomas, has been presently studied. A synergism between ONC and LVT in inducing the cytostatic and cytotoxic effects was observed. The cytostatic effect, seen during the early phase of the treatment with this combination of drugs was manifested as prolongation of the cell cycle duration, especially of the G1 phase; cell death was apparent after 72 h of treatment. The synergistic effect of ONC and LVT was also evident in the clonogenicity assays. Both LVT lactone and its in vitro activated beta-hydroxy acid form, alone and in respective combinations with ONC, exerted similar degree of growth suppression. The effects of both forms of LVT (used alone or in combination with ONC) were reversed by MVA, which suggests that HMG-CoA reductase inhibition is a primary mechanism of LVT action. The data indicate that the LVT lactone can be activated intracellularly by tumour cells studied, and that the combination of ONC with LVT can produce significantly enhanced anti-tumour activities.

ras oncogene product p21 expression and prognosis of human ovarian tumors

Monoclonal antibody rp-28 directed against the ras gene product p21 has been studied to evaluate ras p21 expression in malignant and benign ovarian tissues. Some ovarian carcinomas of serous and mucinous cystadenocarcinomas, undifferentiated adenocarcinomas, and clear cell carcinomas demonstrated intense staining of ras p21. The frequency and intensity of ras p21 staining were observed to increase with the degree of malignancy. There was no significant difference in ras p21 expression between early and late stages in ovarian tumors arising from the coelomic epithelium. With respect to prognosis, no differences between the ras p21-positive and -negative cases in ovarian tumors arising from the coelomic epithelium were observed. It is, therefore, possible to say that ras p21 expression was not related to clinical staging and prognosis. Expression of ras p21 in malignant lesions was higher than that in benign lesions of the ovary, and the expression is associated with the degree of malignancy in some types of ovarian tumors. Overexpression of ras p21 was observed in epithelial tumors; however, increased expression was not observed in germ cell and sex-cord stromal tumors. This differential expression of ras p21 is due to the different histogenesis of ovarian tumors. This fact may reflect a different carcinogenic mechanism for different types of malignancy.

Ha-ras polymorphisms in epithelial ovarian cancer

Unusual restriction fragment length polymorphisms (RFLPs) of the Ha-ras locus have been found in DNA from leukocytes and tumor tissue of cancer patients. To determine whether rare alleles would be observed frequently in patients with ovarian cancer, Ha-ras RFLPs were studied in DNA from 42 different ovarian epithelial tumors and from the peripheral blood leukocytes of 76 normal individuals. Four common, seven intermediate, and seven rare alleles were detected overall. Similar fractions of rare alleles were found in DNA from ovarian cancers and from the peripheral blood of normal individuals. Thus, the frequency of unusual Ha-ras RFLPs did not distinguish patients with ovarian cancers from apparently healthy individuals.

c-myc over-expression in human primary ovarian tumours: its relevance to tumour progression

Expression of the c-myc gene was analyzed in 56 human primary ovarian cancer tissues, including 51 common epithelial and 5 non-epithelial tumours to determine molecular events in the carcinogenic process in ovaries. Over-expression of the c-myc gene was found in 37.3% of all ovarian tumour tissues, and in 63.5% of serous adenocarcinoma tissues. Significant over-expression of the c-myc gene at Stage III compared with other stages, and one remarkable case of over-expression in a serous tumour of low malignant potential suggest that c-myc expression is temporarily activated at some stage(s) during tumorigenesis of ovarian cancer, especially of serous tumours.

Low incidence of point mutation at codon 12 of K-ras proto-oncogene in squamous cell carcinoma of the upper aerodigestive tract

Forty-two cases of squamous cell carcinoma arising in the upper aerodigestive tract were examined to determine the incidence and type of point mutation in codon 12 of the c-K-ras gene by using the polymerase chain reaction and oligonucleotide hybridization techniques on DNA extracted from paraffin blocks. DNA sequencing, in addition, was performed in 4 cases. No point mutation was detected in codon 12 of c-K-ras in the 42 squamous cell carcinomas we examined. According to the results of DNA sequencing of 4 cases, codon 13 also revealed no point mutation. Thus, point mutational activation of codon 12 of c-K-ras oncogene is an uncommon event in human upper aerodigestive tract squamous cell carcinoma.

Analysis of oncogene alterations in human endometrial carcinoma: prevalence of ras mutations

The molecular genetics of human endometrial carcinoma have yet to be defined to any significant extent. Cell lines from 11 endometrial carcinomas were examined for alterations in proto-oncogenes that might predictably be present, based on existing data from the better-characterized human carcinomas of the uterine cervix, ovary, and breast. Codons 12, 13, and 61 of the Ha-ras, Ki-ras, and N-ras genes were examined for possible point mutations, and the c-erbB2/neu, c-myc, and epidermal growth factor receptor (EGFR) genes were examined for amplification or overexpression. Ras mutations were found in seven of 11 (64%) tumors, including three in codon 61 of Ha-ras (CAG----CAT) and four in codon 12 of Ki-ras (GGT----GAT in two and GGT----GTT in two). No evidence was found for amplification or overexpression of the c-erbB2 or EGFR genes in any tumor. One tumor contained amplified c-myc sequences and exhibited relative overexpression of c-myc. These data suggest that the amplification or overexpression of several proto-oncogenes frequently observed in other human gynecologic and breast tumors are not prevalent in endometrial carcinoma and that ras gene mutations are relatively common in this tumor type.

Association of EGF receptor expression with proliferating cells and of ras p21 expression with differentiating cells in various skin tumours

The localization of DNA replicating cells, epidermal growth factor (EGF) receptor-expressing cells and ras oncogene product p21 (p-21ras) positive cells were examined in various skin tumours to elucidate the role of EGF receptor and p21ras in the epidermis. Normal skin, keratoacanthoma (KA), solar keratosis (SK), Bowen's disease (BD), squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and extramammary Paget's disease (PD) were studied. EGF receptors were seen in proliferating layers, where DNA replicating cells localize, but p21ras was found in the more differentiated layers. We conclude that EGF receptor expression is closely associated with cellular proliferation, but p21ras may play a role in the differentiation of cells in various skin tumours.

Protooncogene amplification and tumor ploidy in human ovarian neoplasms

DNA from 24 ovarian tumors, including 16 carcinomas, was examined for amplification of the proto-oncogenes c-myc, int-2, and rc-erbB-2. All cases of carcinoma were also examined by flow cytometry for DNA ploidy and cell cycle analysis, and eight cases of carcinoma were examined for estrogen and progesterone receptors. Protooncogene amplification was not detected in the DNA of benign ovarian neoplasms, or of ovarian carcinomas with low malignant potential. Amplification of c-myc was detected in six of 12 cases of invasive carcinoma, int-2 amplification was present in one case, and c-erbB-2 amplification was not detected in any case. Among the seven cases evidencing protooncogene amplification, three cases showed aneuploidy in tumor DNA, while four showed diploidy. Two cases which showed aneuploidy in tumor DNA did not demonstrate any degree of protooncogene amplification. Protooncogene amplification was frequently associated with morphologic nuclear anaplasia and high mitotic count. Six of the seven cases demonstrating c-myc or int-2 were of the serous type or showed some degree of serous differentiation, while none of the four cases of purely mucinous carcinoma had evidence of amplification. While the total number of cases in the study was limited, it would appear from the trend demonstrated by the data that protooncogene amplification (particularly c-myc) may be involved in the pathogenesis of aggressive common epithelial tumors of the ovary.

Chromosome aberrations in metastatic ovarian cancer: relationship with abnormalities in primary tumors

Twenty malignant effusions secondary to ovarian cancer have been cytogenetically analyzed directly and after short in vitro culture. With the exception of one sample characterized by trisomy 3, all cases displayed clonal structural rearrangements. Chromosomes 1 and 3 were most frequently involved in the genesis of markers. Abnormalities of chromosomes 5, 6, 9, 11 and 12 were also recurrently found, and double minutes (DM) were observed in 2 samples. Our results agree with previous findings on the preferential involvement of chromosomes 1, 3 and 6 in ovarian carcinomas, and suggest that rearrangements of certain chromosomes are non-random but are secondary to the malignant progression of these tumors.

Determination of cellular oncogene rearrangement or amplification in ovarian adenocarcinomas

Four cellular oncogenes, fos, myc, Ha-ras, and Ki-ras, are routinely expressed in ovarian adenocarcinomas. To determine whether the molecular lesion in ovarian carcinoma was a genetic rearrangement or amplification of expressed oncogenes, we examined the myc, Ha-ras, Ki-ras, and fos oncogenes in 14 serous adenocarcinomas of the ovary using molecular hybridization techniques. Using a series of diagnostic restriction endonucleases and gene-specific deoxyribonucleic acid probes, we found no evidence of rearrangement of these genes. In addition, we found no evidence of amplification of the cellular oncogenes analyzed in this series of ovarian tumors. Therefore genetic rearrangement or amplification of these cellular oncogenes is not the primary molecular lesion leading to their expression in ovarian carcinomas.

Amplification of c-ras-Ki oncogene in human ovarian tumours

Amplification of the c-ras-Ki oncogene has been the most consistent finding reported in studies on oncogene activation in ovarian cancer, but for the most part the studies have been small and the results conflicting. In order to determine whether amplification occurred de novo in primary tumours or was associated with tumour progression and metastasis, 81 tumour samples from different sites in 26 patients with ovarian tumours and 7 xenografted ovarian tumour cell lines were assayed. Amplification of c-ras-Ki occurred infrequently and was apparent in a single metastatic site in a patient with poorly differentiated serous cystadenocarcinoma of the ovary. Ten-fold amplification of the c-ras-Ki oncogene was also evident in a benign ovarian fibroma. Amplification of the c-ras-Ki oncogene is rare in ovarian tumours and does not appear to play a fundamental role in tumor development or progression.

Expression of c-myc oncogene product and ras family oncogene products in various human malignant lymphomas defined by immunohistochemical techniques

The authors studied the expression of c-myc and ras family oncogene products in 43 cases of malignant lymphoma (ML) using the immunoperoxidase method. Unfixed frozen sections of lymph nodes from four patients with Hodgkin's disease and 39 with non-Hodgkin's lymphoma, together with normal lymph nodes, were studied by the avidin-biotin-peroxidase complex (ABC) technique. Two monoclonal antibodies, MYC-2 raised against recombinant human c-myc protein (reacting specifically with the c-myc products P62 and P67) and RASK-4 (raised against recombinant P21 and reacting specifically with ras-family product P21) were used. The c-myc product was detected in nuclei of ML cells and some normal, mainly germinal center, lymphocytes. When the staining intensity shown by normal germinal-center lymphocytes was graded as positive (+) or weakly positive (+/-), a very intensely positive reaction ( to ++) was observed in 37 cases (86%) of ML, a positive reaction (+) in four cases (9.3%), and a weakly positive reaction (+/-) in two cases (4.7%). The ras family oncogene product reaction was intensely positive (++) in two cases (4.7%), positive (+) in 16 cases (37.2%), weakly positive (+/-) in 13 cases (30.2%), and negative in 12 cases (27.9%). Western blot analysis confirmed an elevated level of c-myc products in two cases, which showed intense MYC-2 staining, and of ras family products in one case, which demonstrated intense RASK-4 staining. The enhanced expression of these gene products may play an important role in lymphomagenesis of such cases.

A unique pattern of proto-oncogene abnormalities in ovarian adenocarcinomas

Twelve cases of ovarian adenocarcinoma were studied for alterations in proto-oncogenes, and a unique pattern of altered ras proto-oncogenes was observed. Amplification of ras-Ki was found in three of seven ovarian tumors and amplification of ras-Ha in one of 12. In contrast, ras-Ha amplification was not found in any of the 334 other tumors and ras-Ki amplification was only seen in breast cancer at a frequency of 3%. Other proto-oncogenes altered in ovarian adenocarcinomas included c-myc and c-erbb-2. Proto-oncogene abnormalities were more frequent in aggressive tumors of high histologic grade.

Deployment of short-term assays for the detection of carcinogens; genetic and molecular considerations

The deployment of short-term assays for the detection of carcinogens inevitably has to be based on the genetic alterations actually involved in carcinogenesis. This paper gives an overview of oncogene activation and other mutagenic events connected with cancer induction. It is emphasized that there are indications of DNA alterations in carcinogenicity, which are not in accordance with "conventional" mutations and mutation frequencies, as measured by short-term assays of point mutations, chromosome aberrations and numerical chromosome changes. This discrepancy between DNA alterations in carcinogenicity and the endpoints of short-term assays in current use include transpositions, insertion mutations, polygene mutations, gene amplifications and DNA methylations. Furthermore, tumourigenicity may imply an induction of a genetic instability, followed by a cascade of genetic alterations. The evaluation of short-term assays for carcinogenesis mostly involves two correlations that is, between mutation and animal cancer data on the one hand and between animal cancer data and human carcinogenicity on the other. It should be stressed that animal bioassays for cancer in general imply tests specifically for the property of chemicals to function as complete carcinogens, which may be a rather poor reflection of the actual situation in human populations. The primary aim of short-term mutagenicity assays is to provide evidence as to whether a compound can be expected to cause mutations in humans, and such evidence has to be considered seriously even against a background of negative cancer data. For the evaluation of data from short-term assays the massive amount of empirical data from different assays should be used and new computer systems in that direction can be expected to provide improved predictions of carcinogenicity.

c-K-ras codon 12 GGT-CGT point mutation. An infrequent event in human lung cancer

Hu-c-ras represent a family of oncogenes which are capable of inducing malignant transformation in the NIH/3T3 mouse cell line. Associated with this transformation are specific point mutations observed in the 12th and 61st codon of c-K-ras and N-ras and c-Ha-ras, respectively. These base changes generate, in some instances, a new restriction enzyme cleavage site and a restriction fragment length polymorphism (RFLP). One such RFLP has recently been reported for the mutation GGT-CGT at codon 12 of c-K-ras. Our data suggest that this point mutation is rarely present in human lung cancer and therefore is not likely to play a major role in cancer development.

Isolation of ras GTP-binding mutants using an in situ colony-binding assay

We have developed a strategy to isolate mutant ras genes encoding proteins defective in GTP binding. Random in vitro mutagenesis of a v-Harvey (Ha)-ras expression vector was followed by an in situ GTP-binding assay on lysed bacterial colonies. Single amino acid substitutions at ras codon 83, 119, or 144 decreased the affinity of p21 for GTP by a factor of 25-100 primarily as a consequence of increased rates of dissociation of GTP from p21. Nevertheless, these mutant genes induced transformation of NIH 3T3 cells with efficiencies comparable to wild-type v-Ha-ras. In transformed cells, mutant p21s were phosphorylated to a degree similar to that of wild-type v-Ha-ras p21, suggesting that a decrease in affinity by a factor of 100 did not prevent the mutant ras protein from binding GTP in vivo. These results are discussed with respect to the role of GTP in the regulation of p21 function.

Enhanced spontaneous metastasis of mouse carcinoma cells transfected with an activated c-Ha-ras-1 gene

To investigate whether the presence of an activated ras oncogene influences the ability of tumour cells to metastasize, the c-Ha-ras-1 oncogene cloned from EJ/T24 cells was introduced into MT1 Cl.5/7 mouse mammary carcinoma cells. Since the MT1 Cl.5/7 cells are already tumorigenic but have a low metastatic capacity, this experimental design allows a distinction to be made between the effects of the ras gene on metastasis and tumorigenicity. MT1 Cl.5/7 containing the EJ c-Ha-ras-1 metastasized more readily and to more tissue sites than control cells (2.8 sites/mouse vs 0.9 sites/mouse). The metastases expressed the EJ c-Ha-ras-1 p21 ras proteins; however, one metastasis was discovered that had lost the expression of the c-Ha-ras-1 gene. When these cells were re-tested for metastasis, the rate of metastasis was indistinguishable from that of controls. This observation, coupled with a demonstration that lung colonization potential following intravenous inoculation is unaffected by the presence of the activated ras gene, argues that the effect of mutant ras genes is exerted on the ability of cells to escape from the primary tumour, rather than on a survival in the circulatory systems and ability to seed a second site.

Biological and biochemical properties of human rasH genes mutated at codon 61

Using site-directed mutagenesis, we have introduced mutations encoding 17 different amino acids at codon 61 of the human rasH gene. Fifteen of these substitutions increased rasH transforming activity. The remaining two mutants, encoding proline and glutamic acid, displayed transforming activities similar to the normal gene. Overall, these mutants vary over 1000-fold in transforming potency. Increased levels of p21 expression were required for transformation by weakly transforming mutants. The mutant proteins were unaltered in guanine nucleotide binding properties. However, all 17 different mutant proteins displayed equivalently reduced rates of GTP hydrolysis, 8- to 10-fold lower than the normal protein. There was no quantitative correlation between reduction in GTPase activity and transformation, indicating that reduced GTP hydrolysis is not sufficient to activate ras transforming potential.

A dot-blot screening procedure for mutated ras oncogenes using synthetic oligodeoxynucleotides

To analyze human tumors for the presence of mutated ras oncogenes, a procedure was developed based on selective hybridization of mutation-specific oligodeoxynucleotide probes to genomic DNA [Bos et al., Nucl. Acids Res. 12 (1984) 9155-9163]. We have improved this procedure both in sensitivity and speed by including an in vitro amplification step of ras-specific sequences. This amplification step has first been described by Saiki et al. [Science 230 (1985) 1350-1353] and results in a more than 10(4)-fold increase in the sequence which might contain the mutation. Furthermore, we have improved the selectivity of our hybridizations. As a result, mutated ras oncogenes can now be detected with a dot-blot screening procedure requiring less than 1 microgram of tumor DNA.

Purification and characterization of human H-ras proteins expressed in Escherichia coli

The full-length normal and T24 mutant human H-ras proteins and two truncated derivatives of the T24 mutant were expressed efficiently in Escherichia coli. The proteins accumulated to 1 to 5% of total cellular protein, and each was specifically recognized by anti-ras monoclonal antibodies. The two full-length proteins as well as a carboxyl-terminal truncated derivative (deleted for 23 amino acid residues) were soluble upon cell lysis and were purified to 90% homogeneity without the use of denaturants. In contrast, an amino-terminal truncated ras derivative (deleted for 22 amino acid residues) required treatment with urea for its solubilization. The guanine nucleotide binding activity of these four proteins was assessed by a combination of ligand binding on proteins blots, immunoprecipitation, and standard filter binding procedures. The full-length proteins showed similar binding kinetics and a stoichiometry approaching 1 mol of GTP bound per mol of protein. The showed similar binding kinetics and a stoichiometry approaching 1 mol of GTP bound per mol of protein. The carboxyl-terminal truncated protein also bound GTP, but to a reduced extent, whereas the amino-terminal truncated protein did not have binding activity. Apparently, the carboxyl-terminal domain of ras, although important for transforming function, does not play a critical role in GTP binding.