Immunocytochemical demonstration and significance of p21 ras family oncogene product in benign and malignant breast disease

CARCINOGENICITY OF MALATHION AND ESTROGEN IN AN EXPERIMENTAL RAT MAMMARY GLAND MODEL

Breast cancer is considered a major and common health problem in both developing and developed countries. The etiology of breast cancer, the most frequent malignancy diagnosed  in women in the western world, has remained unidentified. Chemicals as the  organophosphorous pesticide malathion have been used to control a wide range of sucking  and chewing pests of field crops, and are involved in the etiology of breast cancers. The  association between breast cancer initiation and prolonged exposure to estrogen suggests  that this hormone may also have an etiologic role in such a process. However, the key  factors behind the initiation of breast cancer remain to be elucidated. The effect of  environmental substances, such as malathion and estrogen was analyzed in an experimental rat mammary gland model. Different cytoplasmic proteins are key in the transformation of a  normal cell to a malignant tumor cell and among these are the Ras super family and Ras  homologous A (Rho-A). Both types of proteins were greater in animals treated with  malathion than those with estrogens. E-Cadherins constitute a large family of cell surface  proteins.

Resultsshowed greater expression of E-Cadherin and vimentin than c-Ha-ras and Rho-A in  rats treated by estrogens. In breast cancer, analysis using immunohistochemical markers is  an essential component of routine pathological examinations, and plays an important role in  the management of the disease by providing diagnostic and prognostic strategies.

The aimof the present study was to identify markers that can be used as a prognostic tool for breast cancer patients.

Elevated serum RAS p21 is an independent prognostic factor in metastatic breast cancer

Background

An important component of the RAS signalling pathway, the RAS p21 oncogene, is frequently hyperactivated in breast cancer. Its expression in tumor tissue has been linked to poor clinical outcome. This study was designed to evaluate the clinical relevance of RAS p21 levels in peripheral blood in a large cohort of metastatic breast cancer patients.

Methods

Two hundred fifty-one patients with metastatic breast cancer were enrolled in this prospective, multicentre, open-label, non-randomized study. Blood samples were collected before start of first-line or later-line treatment. RAS p21 was determined using a sandwich-type ELISA immunoassay. For the determination of the cutoff, blood samples from age-matched healthy controls were analyzed. A value above 452 pg/ml was regarded as elevated (mean + 2 x SD). In the univariate survival analysis, two other cutoffs were considered as well (50th and 75th percentile of patients, i.e. 229 pg/ml and 320 pg/ml). Circulating tumor cells (CTCs) were detected using the CellSearch system.

Results

29 of 251 (12%) patients had RAS p21 levels above the cut-off level of 452 pg/ml. Clinical-pathological parameters, such as hormone receptor and HER2 status, line of therapy and CTC status, did not correlate with RAS p21 levels. Elevated RAS p21 was significantly associated with shorter progression-free and overall survival in the univariate analysis (median PFS: 3.9 months [95%-CI: 1.8–6.0] for patients with elevated RAS p21 levels versus 8.5 months [95%-CI: 7.4–9.5] with non-elevated levels [p = 0.01]; median OS: 7.1 months [95%-CI: 0.3–14.2] versus not reached [p = 0.002], respectively). When RAS p21 cutoffs other than 452 pg/ml were considered, elevated RAS p21 was significantly associated with OS but not with PFS. Classical clinical-pathological factors were included into a multivariate Cox regression analysis. In addition, factors previously shown to influence survival in a univariate analysis, such as serum HER2, CAIX and TIMP1, were included as well. In the multivariate analysis, RAS p21, presence of ≥5 CTCs per 7.5 ml blood, higher grading and higher line of therapy remained independent predictors of shorter OS.

Conclusions

Metastatic breast cancer patients with elevated levels of circulating RAS p21 have significantly worse clinical outcome. Hypothetically, these patients might benefit from therapeutic strategies targeting RAS pathway.

Trial registration

Current Controlled Trials ISRCTN59722891 (DETECT); trial registration date: April, 17th 2010; the trial was registered retrospectively.

Ras protein expression as a marker for breast cancer

Breast cancer, the most common neoplasm in women of all ages, is the leading cause of cancer-related mortality in women worldwide. Markers to help to predict the risk of progression and ultimately provide non-surgical treatment options would be of great benefit. At present, there are no available molecular markers to predict the risk of carcinoma in situ progression to invasive cancer; therefore, all women diagnosed with this type of malignancy must undergo surgery. Breast cancer is a heterogeneous complex disease, and different patients respond differently to different treatments. In breast cancer, analysis using immunohistochemical markers remains an essential component of routine pathological examinations, and plays an import role in the management of the disease by providing diagnostic and prognostic strategies. The aim of the present study was to identify a marker that can be used as a prognostic tool for breast cancer. For this purpose, we firstly used an established breast cancer model. MCF-10F, a spontaneously immortalized breast epithelial cell line was transformed by exposure to estrogen and radiation. MCF-10F cells were exposed to low doses of high linear energy transfer (LET) α particles (150 keV/μm) of radiation, and subsequently cultured in the presence of 17β-estradiol. Three cell lines were used: i) MCF-10F cells as a control; ii) Alpha5 cells, a malignant and tumorigenic cell line; and iii) Tumor2 cells derived from Alpha5 cells injected into nude mice. Secondly, we also used normal, benign and malignant breast specimens obtained from biopsies. The results revealed that the MCF-10F cells were negative for c-Ha-Ras protein expression; however, the Alpha5 and Tumor2 cell lines were positive for c-Ha-Ras protein expression. The malignant breast samples were also strongly positive for c-Ha-Ras expression. The findings of our study indicate that c-Ha-Ras protein expression may be used as a marker to predict the progression of breast cancer; this marker may also ultimately provide non-surgical treatment options for patients who are at a lower risk.

Immunohistochemical Expression of N-ras Oncogene is a Late Event in Head and Neck Carcinomas

This study investigated the expression of the N-ras oncogene in routinely processed tissue sections from 133 patients with squamous cell carcinoma of the head and neck (SCCHN) by immunohistochemistry using anti-N-ras monoclonal antibody. N-ras expression was present in 67 of 133 (49.6%) cases. There was a highly significant correlation between N-ras expression and clinical stage of disease (P=0.003). This study confirmed that overexpression of the N-ras oncogene is common in SCCHN and that it may be an important event in the late stage of disease.

Immunohistochemical detection of the H-ras, K-ras, and N-ras oncogenes in squamous cell carcinoma of the head and neck

The expression of H-ras, K-ras and N-ras oncogenes was analyzed on frozen sections of squamous cell carcinoma of the head and neck (SCCHN) by immunohistochemistry using anti-ras monoclonal antibodies. Of 22 primary SCCHN, 15 (68%) stained positive for H-ras, 10 (45%) for K-ras and seven (32%) for N-ras. Thirteen specimens (59%) stained positive for at least two anti-ras monoclonal antibodies. The presence of immunohistochemically detectable H-ras, K-ras and N-ras proteins was most frequently associated with an increase in tumor size and later stages of disease (T3 and T4), with no apparent correlation with lymph node involvement, site of occurrence, degree of differentiation, age, sex, or race. Thus, overexpression of members of the ras gene family occurs as a relatively common even in SCCHN and may be an important event in the later stages of tumorigenesis.

Activated oncogenes and putative tumor suppressor genes involved in human breast cancers

Cytogeneticists first proposed that the karyotypic abnormalities identified on chromosomes 1, 3, 6, 11, 13, 16, 17, and 18 supported a genetic basis for breast cancer. Such abnormal banding patterns, however, may represent either loss-of-function or gain-of-function molecular events. RFLP analyses have since confirmed that 20-60% of primary and spontaneous human breast tumors exhibit allelic losses on these same chromosomes, although the exact genes involved at these chromosomal sites remain largely unknown. Knowledge gained about the Rb-1 and p53 tumor suppressor genes at 13q14 and 17p13 in breast and other human tumors supports the paradigm that for any chromosomal locus, allelic loss associated with a mutation in the remaining tumor allele signifies an involved tumor suppressor gene. Given this paradigm, there are nearly a dozen putative breast tumor suppressor genes under active investigation, with most investigators now focusing on various chromosome 17 loci. Among the known proto-oncogenes found activated in breast cancer, amplification of c-erbB-2 at 17q21 is the most widely studied and clinically significant gain-of-function event uncovered to date, occurring in about 20% of all primary breast tumors. The involvement of this overexpressed membrane receptor has engendered interest in related tyrosine kinase receptors, such as EGFR, IR, and IGF-I-R, as well as their respective ligands, which may be overexpressed in a greater fraction of tumors, contributing to the autocrine and paracrine regulation of breast cancer growth and metastasis. New attention is being given to the potentially oncogenic function of structurally altered nuclear transactivating steroid hormone receptors, such as ER, whose overexpression has long been used to determine endocrine therapy and prognosis for individual breast cancer patients. While c-myc was one of the first known proto-oncogenes to be found amplified and overexpressed in human breast cancers, the actual incidence and clinical significance of its activation remain disputed and in need of further study. Lastly, we can expect greater clarification about the importance of various 11q13 genes found coamplified in nearly 20% of primary breast cancers, and pursuit into the intriguing possibility that a cyclin-encoding gene represents the overexpressed locus of real interest in this amplicon. Virtually all of these important genetic abnormalities identified thus far are associated with but not restricted to human breast cancers. The absence of identifiable molecular defects relating to the tissue specificity of this malignancy must be considered a substantial gap in our basic understanding of breast carcinogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

Oncogenes and tumour-suppressor genes in squamous cell carcinoma of the head and neck

Cancer is now considered to be a multi-hit process which involves a number of aberrant genetic events culminating in malignant transformation. In squamous cell carcinoma (SCC) of the head and neck the action of both oncogenes and tumour-suppressor genes has been identified during the course of the disease. Cytogenetic analysis of these carcinomas has demonstrated chromosomal breakpoints, particularly in the regions of 1p22 and 11q13 together with frequent amplification of the proto-oncogenes in the 11q13 amplicon; int-2, hst-1 and bcl-1. Ras mutations have been infrequently identified in the Western World whereas ras over-expression has been a common finding and may be associated with the early development of head and neck cancer. C-myc over-expression appears to correlate with a poor prognosis for these patients. The tumour-suppressor gene p53 is also thought to be involved in the development of SCC in head and neck tumours and its aberrant expression is associated with a history of heavy smoking and heavy drinking. E-cadherin, a putative tumour-suppressor gene is down-regulated in poorly differentiated head and neck SCC and maybe important in nodal metastasis. A recent study has indicated that the Human Papilloma Virus (HPV 16 and 33) has a role in the aetiology of tonsillar carcinomas and HPV has been shown to produce transforming proteins which bind to and inactivate the p53 tumour suppressor gene. This evidence suggests that the possibility of a viral mechanism for the development of SCC in the head and neck should be considered. This paper proposes a series of genetic events to explain the development of SCC of the head and neck.

Ras p21 in breast tissue: associations with pathology and cellular localisation

Immunocytochemistry with monoclonal antibody Y13-259 demonstrated p21 ras in paraffin sections of breast tissue from 171 women: 85 with invasive breast carcinoma, 14 with non-invasive carcinoma and 72 with benign changes only. Many different tissue elements contributed to ras expression. Semiquantitative assessment showed that intensity of immunostaining in the normal epithelium of large ducts, small extralobular ducts and terminal duct lobular units (TDLU) was usually exceeded by that of myoepithelial cells. Vascular smooth muscle and apocrine epithelium also stained strongly, but the flat epithelial cells lining cysts did not express detectable p21 ras. There was a progressive increase from normal epithelium through epithelial hyperplasia of usual type and atypical hyperplasia to carcinoma in situ, without further increase in invasive carcinoma. Expression in carcinomas was inversely related to oestrogen receptor content but independent of the prognosis-associated variables of size, histological type, vascular invasion or lymph node metastasis.

Diagnostic utility of oncogenes and their products in human cancer

The first clear cut association of an oncogene with a specific cancer is the c-abl translocation in chronic myelogenous leukemia and acute lymphocytic leukemia; it has been observed in 90% of CML cases examined. This is the major contributing factor to its being the target of the first oncogene-based FDA-approved diagnostic test. Although the role of the abl translocation in the tumorigenic process is not yet understood, it is clear that somehow it must be causally related to the disease, and thus is an ideal target for a diagnostic test. The association of this oncogene with a specific cancer is the model on which all others may be based in the future. Second generation tests could easily include PCR on mRNA, and/or in situ hybridization, both of which could be performed using blood samples. Both methods would provide a faster means of testing a large number of cells, however, the methodologies must be improved through automation and computer-aided image analysis, respectively, in order to become useful routine tests. Both neu and epidermal growth factor receptor (EGFR) appear to have a close correlation between overexpression of the gene product and outcome of disease in breast cancer; valuable information for prognosis of the disease. And again, although the actual mechanism of action of these molecules and how this relates to the tumorigenic process is not yet known, it is believed from the very nature of the molecules that they must in some way contribute to the progression of the disease. In both cases, the protein products are overexpressed in tissue, and in the case of Neu, it appears as through at least some of the patients have a Neu-related protein in their serum. These molecules present relatively easy targets for the development of diagnostic/prognostic assays, as antibodies are easily made and can be incorporated into a variety of assay formats. Current assays available, an ELISA for Neu and a radio-ligand binding assay for EGFR, are highly sensitive, reproducible and relatively easy to perform. Only the ELISA is commercially available, however, and hence allows for easy comparison between laboratories. An abvious step towards the routine measurement of EGFR then is the development of a comparable commercially available test. An improvement for both types of assay would be the incorporation of an internal control to gauge the cellular component of the tissue samples that are tested. The outcome of the applications of myc and ras to cancer diagnostics is not so easily predictable, with a couple of exceptions.(ABSTRACT TRUNCATED AT 400 WORDS)

Oncogenes: a review of their clinical application

One objective of this review is to sort through and collate the recent data that suggest that human cellular oncogenes, which have been implicated as the etiologic agents in both animal and human malignancies, have also the potential to be employed as clinical tools in the struggle against cancer. For nearly 10 years, reports have been suggesting that advantage can be taken of cellular oncogenes as to their use as diagnostic and prognostic indicators of cancer and eventually as therapeutic cancer agents. It is also the purpose of this review to give an objective evaluation of these predictions. Moreover, this review will try to highlight some of the significant advances in this most rapidly evolving field of biology. Although the enormity of what has been learned about cellular oncogenes is nothing less than impressive, it is the view here that the routine implementation of oncogenes into the clinical setting will not become evident as early as the many predictions had purported.

Monoclonal antibodies for radioimmunoscintigraphy of breast cancer

Breast cancer is the leading cause of cancer deaths among females, and it is estimated that each year, one in ten American women will be newly diagnosed as having the disease. It is therefore not surprising, that a great deal of effort has been made to better understand the biology of breast cancer, and that investigators keep up the search for new tools to better characterize, diagnose and treat these tumours. In this regard, the introduction of the hybridoma technique in 1975 by Kohler and Milstein has lead to an extensive work in the characterization of monoclonal and polyclonal antibodies against breast cancers. A large number of antibodies has been raised to different epitopes present in normal and neoplastic breast tissue; but unfortunately we have yet to find a highly sensitive and specific monoclonal antibody for breast cancer that can successfully be used for scintigraphic detection of nodal metastases and for radioimmunotherapy treatment of this disease. As possible radioimmunodiagnostics, antibodies are known which react with the following antigens: (1) cytoskeletal proteins (2) breast cell products (3) steroid receptors (4) putative tumor-associated antigens (5) oncogene products (6) pregnancy-related products (7) basement membrane antigens (8) degradative enzymes (9) cell receptors for extracellular matrix molecules (10) multidrug resistance gene product (p-glycoprotein) (11) proliferative markers.

Quantitative immunofluorescence, anti-ras p21 antibody specificity, and cellular oncoprotein levels

A general approach to investigating specificity and saturation of antibodies by quantitative immunofluorescence is applied to monoclonal antibodies generated against p21 or ras oligopeptides to quantify ras p21 oncoprotein in cultured cells. Ras 10, a panreactive mouse monoclonal antibody, appears to be a superior probe for detection of p21 in cell extracts or fixed cells because it binds a 21 kD protein on SDS-PAGE/western blots and labels the cytoplasmic membrane in a saturable and competitive manner. RAP-5, a widely used mouse monoclonal antibody generated against an oligopeptide of ras p21, does not recognize p21 in denaturing immunoblots or in immunofluorescence of cultured cells.

Evidence of enhancement of the ras oncogene protein product (p21) in a spectrum of human tumors

Using a direct binding liquid competition radioimmunoassay, the amount of the ras oncogene protein product, p21, was quantitated in a variety of human tumors and adjacent apparently normal tissues. In 48 of 50 matched tumor and normal tissue biopsy specimens from 50 patients, more ras p21 was detected in the tumor than in its normal counterpart. Twenty-five of 28 breast tumors demonstrated more ras p21 than the average of the values obtained for fibroadenomas. Furthermore, in 17 of the 19 cases studied, over 20% more ras p21 was observed in breast carcinomas compared with their respective normal counterparts. More ras p21 was also demonstrated in the majority of tumors of the stomach, lung, colon and bladder compared with their respective adjacent normal tissues. Our data therefore indicate that ras p21 expression is quantitatively enhanced in many human tumors originating from several different tissue types.

p21 ras protein expression in benign and malignant human breast

The ras oncogenes encode for GTP binding and GTPase active proteins of relative molecular mass 21,000 (p21ras) which are involved in the transduction of stimuli for cell proliferation. There have been conflicting reports about the detection and significance of expression of p21ras protein in human breast disease as determined by immunohistochemistry. The antibody Y13-259, which detects a single protein of Mr 21,000, has been applied immunohistochemically to frozen sections of normal, benign proliferative breast, fibroadenomas, and carcinomas. Uniform staining of normal breast epithelium and myoepithelium was found, with occasional stronger staining in areas of epithelial hyperplasia in benign breast disease. Contrary to previous reports, decreased expression, usually heterogeneous, was found in half of the carcinomas examined. Thirty per cent of the carcinomas exhibited heterogeneous staining stronger than that of normal breast, interpreted as increased expression of p21ras protein. This did not relate to tumour grade or node status but showed a significant correlation with proliferation rate as determined by the monoclonal antibody Ki-67. This study confirms previous reports that p21ras protein expression is a feature of normal cells, and has identified increased expression in 30 per cent of tumours associated with higher proliferation rates, which is a lower incidence than previously claimed when a different antibody was employed.

Immunocytochemical demonstration of p21ras in normal and transitional cell carcinoma urothelium

Activation and/or overexpression of the protein product of the ras gene family (p21ras) has been implicated in the development of various cancers, including bladder carcinoma. We have used the anti-p21ras monoclonal antibody, RAP-5, to assess the level and pattern of expression in formalin-fixed, paraffin-embedded tissue sections of both normal and malignant urothelium. All 14 random normal bladder biopsies and 67 of 68 transitional cell carcinomas of the urinary bladder were positively stained with the RAP-5 antibody. In normal urothelium, p21ras staining tended to be localized to the superficial cell layer. With increasing histological grade and/or depth of invasion of the tumour, a greater proportion of tissue sections demonstrated a staining pattern which was more uniform with respect to the different epithelial cell types. Serially diluting the primary antibody did not reveal any significant differences in the staining patterns observed. Despite the change in staining pattern with increasing grade, these results suggest that p21ras expression by itself is not a useful indicator of the malignant phenotype.

Optimal preservation of p21 ras immunoreactivity and morphology in paraffin-embedded tissue

Specific immunostaining of p21 ras protein by the well-characterized pan-ras antibody Y13-259 is achieved in paraffin sections of human and animal tissues fixed in periodate-lysine-paraformaldehyde-dichromate (PLPD). Intensity of staining is as good as in cryostat sections, with superior histological detail. Localization to plasma membrane is demonstrated in rodent cells genetically manipulated to express abundant p21 ras (the FHO5T1 cell line), both in preparations suspended in agar after culture in vitro and in those growing as tumour in vivo. Strong positive staining is observed in neoplasms of human breast and colon, tissues in which there is independent evidence of elevated ras gene expression. The superior morphology afforded by this technique allows clear characterization of p21 ras expression in small premalignant lesions for which other methods of detection of oncogene expression are not appropriate.