INT-2 AND C-ERBB-2 GENE AMPLIFICATION IN UROLOGICAL CANCERS

We analyzed the alteration of int-2, c-erbB-2 and EGFR genes in 32 cases of transitional cell carcinoma of the urinary tract, 15 cases of renal cell carcinoma and 14 cases of prostatic carcinoma by Southern blot hybridization method. Three- to 12 fold amplification of int-2 gene was observed in 4 (12.5%) of 32 transitional cell carcinomas. Of these 4 cases 3 were G3 tumor with muscle invasion and the remaining was G1, pTa tumor with subsequent recurrence of multiple tumors. The other 2 cases (6.3%) with invasive transitional cell carcinoma showed amplification of c-erbB-2 gene. Neither amplification nor gross rearrangement of EGFR gene was detected in transitional cell carcinoma. On the other hand, renal cell carcinomas and prostatic carcinomas had neither amplification nor gross rearrangement of these 3 genes. These results suggest that the int-2 gene located in chromosome locus 11q13 and the c-erbB-2 gene have a specific role in carcinogenesis and in progression of transitional cell carcinoma through their gene amplifications.

The Int-2/Fgf-3 oncogene product is secreted and associates with extracellular matrix: implications for cell transformation

NIH3T3 cells transformed by mouse Int-2/Fgf-3 cDNA express a series of Int-2-related products representing discrete stages of processing and glycosylation. We confirm that in at least two highly transformed clonal lines, Int-2 products acquire further modifications and are efficiently secreted into the culture medium. Secreted proteins become associated with the cell surface and extracellular matrix and can be displaced by addition of soluble glycosaminoglycans, specifically heparin, heparan sulfate, and dermatan sulfate. Increasing concentrations of heparin not only compete for Int-2 binding in a dose-dependent manner but also inhibit the growth of these cells and revert the transformed phenotype. These findings reaffirm the notion that extracellular or surface-bound Int-2 protein is instrumental in the morphological transformation of these cells.

The int-2 proto-oncogene is responsible for induction of the inner ear

The int-2 proto-oncogene encodes several products related to the fibroblast growth factor (FGF) family. FGFs have been associated with mesoderm induction in the amphibian embryo and int-2 has a distinct pattern of expression throughout development in vertebrates. But evidence for a function of int-2 in embryo-genesis has been lacking. In the mouse embryo, int-2 transcripts have been detected in the rhombencephalon at a developmental stage where classical experiments showed that the induction of the inner ear occurs. This raises the possibility that int-2 may constitute a signal for the induction of the otic vesicle, the primordium of the inner ear. We provide direct evidence for this view by showing that (1) the formation of the otic vesicle is inhibited by antisense oligonucleotides targeted to the secreted form of int-2, and by antibodies against int-2 oncoproteins, and (2) basic FGF (bFGF) can mimic the inductive signal in the absence of the rhombencephalon.

The prognostic value of tumor-associated carbohydrate structures correlated with gene amplifications in human breast carcinomas

The effects of cell surface sugar chains combined with certain gene amplifications of breast cancers on the prognosis of patients were studied and the relationships between the sugar chains of cancer cells and amplifications of the proto-oncogenes c-myc, int-2 and c-erb B-2, evaluated. One hundred and fifty three human breast carcinoma tissues were investigated by an immunohistochemical technique using the avidinbiotin-peroxidase method with 1 lectin (HPA; Helix Pomatia) and 4 monoclonal antibodies (B-72-3, St-439, anti-Tn and anti-T). The positive rates of HPA, St-439, B-72-3, anti-Tn and anti-T were 43 per cent (63/153), 52 per cent (80/153), 53 per cent (81/153), 64 per cent (98/153) and 89 per cent (136/153), respectively. Patients whose cancers had positive HPA staining were found to have a lower survival rate than those with negative HPA staining (p less than 0.05), whereas those whose cancers had positive St-439 staining showed a better prognosis than those with negative St-439 staining (p less than 0.01). The positive rate of HPA was related to the gene amplification of c-myc proto-oncogene (p less than 0.01), whereas the negative rate of St-439 was correlated with the gene amplification of c-erb B-2 (p less than 0.01). These data indicate the prognostic value of HPA and St-439 and also the relationships between the gene amplifications and carbohydrate structures in breast cancer cells.

Establishment and characterization of immortalized non-transplantable mouse mammary cell lines cloned from a MMTV-induced tumor cell line cultured for a long duration

During the culturing of a mouse mammary tumor cell line, MuMT73, maintained in vitro for more than a decade, we found morphological heterogeneity in its cells; some showed contact inhibition in their growth, some formed domes and some grew criss cross and piled up. In trying to clone the cell line to isolate cells showing contact inhibition or dome formation, we were able to establish six clonal cell lines. These six cell lines were categorically divided into three groups according to their phenotypical behavior, Groups A, B and C. Group A (clones 1, 5 and 7) cells had a property of contact inhibition. They induced no tumor when injected into the subcutaneous tissue of the back, nor even when injected into the mammary fat pads or under the kidney capsule of syngenic or nude mice, and therefore were thought to be non-malignant in nature. They were positively stained by anti-keratin antiserum and had mouse mammary tumor viruses (MMTVs). Group B (clone 6) cells grew in a crisscross pattern and piled up, and they induced tumors when injected into the subcutaneous tissue of the back of mice. Group C (clones 3 and 4) cells formed domes in their growth and induced some tumors in the mammary fat pads and under the kidney capsule of KSN nude mice. In Southern blots with MMTV-env probe, numerous exogenous MMTV proviruses were detected in these cell lines. The insertion patterns of these proviruses in cells of non-malignant clonal lines (Group A) resembled those of malignant lines (Group B), except one band (about 26 Kb), but were considerably different from those of intermediate lines (Group C). On the other hand, no difference was detected in Southern blots with int-1 or int-2 probes among the non-malignant, intermediate and malignant clonal cell lines.

Decrease of c-erbB-2 and c-myc RNA levels in tamoxifen-treated breast cancer

The c-myc, c-erbB-2, hst and int-2 oncogenes are frequently amplified and/or overexpressed in human breast carcinomas. We studied the effect of tamoxifen on RNA levels of these oncogenes in 19 breast cancer patients treated for 3 weeks prior to surgery as compared with 22 control patients. RNA levels were measured by in situ hybridization coupled with computer-aided quantification. c-myc and c-erbB-2 expression was high in the control population (mean values: 23.4 and 29.1 grains/cell respectively) and significantly decreased in the tamoxifen-treated population (mean values: 14.6 and 7.4 grains/cell respectively) (P = 0.018, P = 0.003 respectively); hst and int-2 RNA levels were low (2-6 grains/cell) and not significantly altered by the treatment. There was a correlation between gene amplification and expression for c-erbB-2 (P = 0.0005) and hst (P = 0.02) in the control population. Elevated c-erbB-2 RNA level was correlated with the absence of estrogen (P = 0.02) or progesterone (P = 0.05) receptors. In the ER+ population, the tamoxifen-treated group had significantly lower c-myc expression levels than the control group (P = 0.04) which is in agreement with the estrogen induction of c-myc in ER+ T47D cell line and its inhibition by antiestrogens. Surprisingly, c-erbB-2 expression in the tamoxifen-treated group was significantly diminished in the ER- (P = 0.02) and PR- (P = 0.01) populations. This effect was not observed in the ER- BT474 cell line. These results suggest that in vivo tamoxifen decreases c-myc and c-erbB-2 RNA levels in breast cancer cells via two different mechanisms. To our knowledge this is the first evidence of in vivo down regulation of a gene by tamoxifen in ER- breast cancer cells.

D11S287, a putative oncogene on chromosome 11q13, is amplified and expressed in squamous cell and mammary carcinomas and linked to BCL-1

Approximately 15 to 20% of primary breast cancers and an even higher proportion of squamous cell carcinomas of the head and neck show amplification of DNA markers on band q13 of human chromosome 11. However, known genes within the amplified region, such as the FGF-related oncogenes INT-2 and HST-1, are very rarely expressed in these tumors. Here we show that another candidate oncogene, designated D11S287, implicated in the pathogenesis of parathyroid adenomas, is also amplified in breast cancers. Significantly, it is consistently coamplified with INT-2 and HST-1 in 36 out of 202 primary tumors, including one case in which the amplified unit did not encompass the translocation breakpoint marker BCL-1. This implies that D11S287 is on the same side of the breakpoint as INT-2, and pulsed-field gel electrophoresis indicates that D11S287 is less than 250 kb from the BCL-1 marker. Since D11S287 RNA was present at elevated levels in a group of tumors and cell lines in which the 11q13 region is amplified, it may be the key oncogene on this amplified unit, and could also be activated by BCL-1 translocations.

GST pi gene is frequently coamplified with INT2 and HSTF1 proto-oncogenes in human breast cancers

The glutathione S-transferase gene (GST pi) is located on the same chromosome band (11q13) as proto-oncogenes INT2 and HSTF1 which are frequently amplified in breast cancer. Using the Southern blot technique, we looked for the amplification of the GST pi gene in 17 fresh tumors from human mammary carcinoma. The tumors were preselected because either they had an amplification of the INT2 proto-oncogene detected by dot blot, or their karyotypes exhibited or did not exhibit homogeneously staining regions, a cytogenetic character indicating amplification. Coamplification of GST pi, HSTF1 and INT2 was observed in five tumors, and coamplification of GST pi and HSTF1 without amplification of INT2 in another tumor. We also observed coamplification of GST pi, INT2, HSTF1 in the mammary carcinoma cell line MDA/MB134, whereas GST pi alone was amplified in the mammary epithelial cell line HBL100. These results indicate that INT2, HSTF1 and GST pi belong to the same large amplicon. Since GST pi is involved in intracellular detoxication and since chemotherapeutic drugs are among its substrates, it will be of interest to study GST pi gene expression as well as the response to chemotherapy in patients presenting this amplicon.

Cell transformation by Int-2--a member of the fibroblast growth factor family

The sequence similarities between Int-2 and members of the fibroblast growth factor (FGF) family have prompted functional as well as structural comparisons with other FGFs. Here we examine the ability of int-2 sequences to induced morphological transformation of NIH3T3 cells, a characteristic property of the secreted FGFs, such as FGF-5 and Hst1/kFGF. Despite encoding a short signal sequence, which directs the product to the secretory pathway, mouse int-2 DNA is incapable of inducing foci of transformation in the standard transfection assay. However, when transfected cells are enriched by co-selection with the neomycin resistance gene, a proportion of the int-2-expressing cells display a transformed phenotype, including the ability to grow as colonies in soft agar and in defined medium. Analyses of int-2 RNA and protein in these cells suggest that transformation by int-2 may require a threshold level of expression, and that the subsequent phenotype is dependent on the level of int-2 protein present in the cells.

Amplification of the int-2 gene in human head and neck squamous cell carcinomas

Head and neck squamous cell carcinomas (SCC) from 21 patients were analyzed for structurally rearranged or amplified proto-oncogenes by Southern blot hybridization. The int-2 proto-oncogene was amplified 3-5 fold in 5 (50%) of 10 laryngeal SCC and 2-3 fold in 5 (45%) of 11 nonlaryngeal SCC of the head and neck. Adjacent histologically normal tissue from the same patients had single int-2 gene copy number. Coamplification of int-2 and the epidermal growth factor receptor (c-erbB-1) gene was found in one laryngeal SCC and one SCC metastatic to the neck. No amplification or structural alterations of proto-oncogenes c-erbB-2/HER2, c-myc, H-ras-1, or K-ras-2 was detected in any of the head and neck tumors. In a survey of head and neck tumor-derived cell lines, int-2 was amplified 9 fold in a hypopharyngeal tumor cell line (FaDu), but not amplified in 3 laryngeal tumor cell lines. int-2 has been localized to the q13 band of chromosome 11. We used chromosome 11 specific probes to demonstrate that int-2 amplification was not due to complete or partial chromosome 11 duplication. int-2 amplification was localized to 11q13, but did not extend to the ets-1 locus 11q23. The results indicate that int-2 is frequently amplified in SCC of the head and neck and suggest that int-2 amplification may correlate with clinical disease progression.

Association of hst gene expression with metastatic phenotype in mouse mammary tumors

From the pregnancy-dependent mouse mammary tumor TPDMT-4, four autonomous sublines were established after its independent progression under different conditions. Despite their similar growth rates in inguinal fat pads, three sublines formed lung metastases, and one did not when they were injected i.v. into mice as a single cell suspension. The TPDMT-4 tumor and the nonmetastatic subline expressed mRNA for the orf gene of mouse mammary tumor virus, whereas all metastatic sublines did not. This suggested that the loss of its expression may have been a prerequisite for the progression toward metastatic ability. To identify the gene(s) participating in the generation and the progression of TPDMT-4, the expression of 23 different oncogenes was analyzed. The expression of int-2 was detected in TPDMT-4 and in all sublines, indicating that TPDMT-4 was generated by activation of this gene, whereas hst expression occurred only in the metastatic sublines. These results demonstrated that the hst gene may contribute to tumor progression from a nonmetastatic to a metastatic phenotype in the mouse mammary tumor system.

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.

The int-2 gene product acts as an epithelial growth factor in transgenic mice

The induction of mammary tumors by mouse mammary tumor virus (MMTV) is thought to occur through proviral activation of one or more cellular genes. One of these, int-2, encodes a 27 kd protein which exhibits striking homology to the basic fibroblast growth factor family. To assess directly the role of the int-2 protein in cell proliferation, we have established transgenic mice which carry the int-2 gene driven by the MMTV promoter/enhancer. Expression of the int-2 gene in female transgenic mice results in pronounced mammary gland hyperplasia. Interestingly, expression of the MMTV-int-2 transgene in the prostate gland of male carriers results in a benign, but dramatic, epithelial hyperplasia similar to benign prostatic hypertrophy (BPH), a common but poorly understood disorder in human populations. Together, these results indicate that the int-2 product can act as a potent growth factor in these epithelial tissues.

Proviral insertions within the int-2 gene can generate multiple anomalous transcripts but leave the protein-coding domain intact

We examined the effects of mouse mammary tumor virus integration on the multiple RNA transcripts expressed from the int-2 proto-oncogene in virally induced breast tumors. Proviral insertion either upstream or downstream of the gene could simultaneously activate transcription from three dissimilar int-2 promoters. In some tumors, the activating provirus lies within the transcription unit and disrupts the structures of the various RNAs. Insertions in the 5' region of the gene had complex effects depending on the orientation and position of the provirus relative to the three promoters and intron-exon boundaries. RNase protection experiments identified transcripts initiated in the viral long terminal repeat, at normal and cryptic sites in the int-2 sequences, and from cryptic promoters in an inverted provirus. AT the 3' end, insertions occurred within the untranslated trailer and provided alternative termination signals that substituted for one or both of the normal the poly(A) addition sites. However, in no instance, of the 20 tumors analyzed in detail, did a provirus perturb the presumed open reading frame of the gene. These data strongly implicate the normal product of the int-2 gene, which is related to the fibroblast growth factor family, as a contributory factor in virally induced mammary tumors.

BCL-1 participates in the 11q13 amplification found in breast cancer

In an attempt to probe the significance of HST and INT-2 gene amplification in human breast carcinomas, we have surveyed the amplification status of five molecular markers located on the long arm of chromosome 11 (BCL-1, HST, INT-2 & SEA on 11q13, and ETS-1 on 11q23) in a population of 297 mammary tumors. ETS-1 was rarely amplified and always independently from the other proto-oncogenes. Concerning band q13: (i) 50 tumors (approximately 17%) were co-amplified for BCL-1, HST & INT-2; (ii) in 3 cases, amplification extended to the SEA gene; (iii) in 6 carcinomas, BCL-1 was the only amplified marker. The fact that we never observed amplification of HST & INT-2 independently of BCL-1, which in turn can be amplified solely, suggests the presence, between HST/INT-2 and BCL-1, of a genetic element which could be important in the development of a subset of mammary tumors.

Characterization of int-2: a member of the fibroblast growth factor family

int-2 was discovered as a proto-oncogene transcriptionally activated by MMTV proviral insertion during mammary tumorigenesis in the mouse. Sequence analysis showed int-2 to be a member of the fibroblast growth factor family of genes. In normal breast and most other adult mouse tissues, int-2 expression was not detected except for low levels in brain and testis. However, using in situ hybridization, expression was found at a number of sites during embryonic development, from day 7 until birth. An analysis of the int-2 transcripts found in embryonal carcinoma cells revealed six major classes of RNA initiating at three promoters and terminating at either of two polyadenylation sites. Despite the transcriptional complexities, all size classes of RNA encompass the same open reading frame. Using an SV40 early promoter to drive transcription of an int-2 cDNA in COS-1 cells, several proteins were observed. These were shown to be generated by initiation from either of two codons: One, a CUG, leads to a product which localizes extensively to the cell nucleus and partially to the secretory pathway. In contrast, initiation at a downstream AUG codon results in quantitative translocation across the endoplasmic reticulum and the accumulation of products ranging in size from 27.5 x 10(3) Mr to 31.5 x 10(3) Mr in organelles of the secretory pathway. These proteins represented glycosylated and non-glycosylated forms of the same primary product with or without the signal peptide removed. These findings suggest the potential for a dual role of int-2; an autocrine function acting at the cell nucleus, and a possible paracrine action through a secreted product.

Proto-oncogene amplification and human breast tumor phenotype

Amplification of c-myc, c-erbB-2, hst and int-2 proto-oncogenes was investigated in two independently collected breast tumor series comprising 292 carcinomas. Differences in the frequencies of amplification could be observed between these two series for c-myc (9.3% vs. 20.8%) and hst/int-2 (21.5% vs. 15.6%) whereas similar values were found for c-erbB-2 (22.5% vs. 20.3%). Statistical correlations between amplification and disease parameters were also dependent on population sampling. Therefore we performed our statistical analysis on the pooled populations and focused on the 219 primary breast carcinomas from patients without therapy prior to surgery. Amplification of c-erbB-2 was strongly correlated to the absence of either estrogen (ER-, P = 0.003) or progesterone (PR-, P = 0.004) receptors. An amplified c-myc was significantly associated with PR- (P = 0.005) and was prevalent in high grade tumors. On the contrary, hst/int-2 amplification was correlated to PR+ tumors (P = 0.01) and was more frequent in ER+ and low grade tumors, and was also correlated with lymph node involvement (P = 0.04). Our data suggest that amplification of each of these proto-oncogenes could be representative of a particular subset of breast tumors. Therefore, proto-oncogene amplification may be helpful in characterizing new biological subclasses in human breast cancer.

A paradigm for oncogene complementation in human breast cancer

Multiple cellular oncogenes are amplified in malignant tumours, and it is possible to invoke gene dosage as a possible base for product activity. In vitro data have shown that two different oncogenes can cooperate in converting a normal cell into one that is tumorigenic. This suggested that multiple cooperative alterations might be involved in cancer progression. Breast cancers have a broad spectrum of clinical behaviours ranging from highly aggressive neoplasms to almost chronic diseases. Fifty months of clinical follow-up were studied in 143 patients with primary breast cancers. Uni- and multivariate analyses were performed in order to determine any synergistic effect of amplified c-myc, erbB-2 and int-2 genes on the disease-free state and overall survival. We showed that c-myc amplification was associated with early recurrence and shorter survival; in contrast, erbB-2 and int-2 extra copies resulted in later relapse events, especially in patients whose tumours showed a normal copy number of c-myc genes. This pointed out sequential activation of complex regulatory cascades within the cell. Such particular behaviour enabled us to categorize erbB-2 and int-2 oncogenes into a group showing delayed action, in contrast to c-myc involvement in rapid spread of the tumour. As expected, co-amplified c-myc and erbB-2 genes showed positive cooperation with respect to recurrence and shortening of overall survival. Finally, the harmful effects of amplified c-myc and erbB-2 oncogenes were dramatically increased in patient subgroups showing a normal copy number of the int-2 gene. Multivariate analysis was used to evaluate disease-free survival and to test for potential interactions of oncogene covariates. It pointed out multiple independent combinations which enabled us to define complementation groups with respect to clinical patient behaviour.

High incidence of coamplification of hst-1 and int-2 genes in human esophageal carcinomas

We analyzed the alteration of the hst-1 and int-2 genes in 36 cases of esophageal squamous cell carcinoma, 42 cases of gastric adenocarcinoma, and 52 cases of colorectal adenocarcinoma. Coamplification of the hst-1 and int-2 genes was observed in 19 of 36 esophageal carcinomas (52%), 16 of 34 primary tumor tissues (47%), and 10 of 10 metastatic tumors (100%). The degree of amplification ranged from 4- to 8-fold. The incidence of hst-1 and int-2 gene coamplification was significantly higher in male patients than that in female patients (P less than 0.05). The coamplification of the hst-1 and int-2 genes had a tendency to correlate with clinical stage. The progesterone receptor gene, which is mapped to chromosome 11 at band q21-23, was not amplified in these esophageal carcinomas. Coamplification of the hst-1 and int-2 gene does not seem to imply increased numbers of chromosome 11, and the hst-1 and int-2 genes appear to be in same amplification unit on chromosome 11 at band q13. No coamplification of the hst-1 and int-2 genes was detected in gastric carcinomas and colorectal carcinomas. These results suggest that amplification of chromosomal locus of the hst-1 and int-2 genes might participate in carcinogenesis, in progression, and particularly in metastasis of esophageal carcinomas.

Mesoderm-inducing properties of INT-2 and kFGF: two oncogene-encoded growth factors related to FGF

Many theories of neoplasia suggest that oncogenic transformations result from aberrations in the control mechanisms which normally regulate growth and differentiation during embryonic development. It has recently become clear that many proto-oncogenes are differentially expressed during embryonic development and may thus be important embryonic regulatory molecules. We report here that the products of two transforming oncogenes int-2 and hst/ks (now called kfgf) can, with different potencies, induce mesoderm formation in isolated Xenopus laevis animal pole explants and stimulate DNA synthesis in mammalian fibroblasts. The results suggest that these proteins may function as mesoderm inducers in mammalian embryogenesis and that similar receptor/signalling pathways may be utilized for developmental and oncogenic processes. Finally, we have shown that the Xenopus assay system used in this study provides a powerful screen for protein factors that are active in development.

The structure and function of the int-2 oncogene

The classification of int-2 as a growth factor is based primarily on the similarities between the predicted amino acid sequence and that of basic fibroblast growth factor (bFGF), as well as other members of this expanding family of related proteins. In this review, we summarise the background to the identification of int-2 as a proto-oncogene in virally induced mouse mammary tumours and describe key features of the structure and expression of both the mouse and human homologues. The normal sites of int-2 expression include specific embryonic cell types suggesting multiple inductive or morphogenetic roles. Recent progress in the characterisation of the int-2 product will be discussed in relation to the similarities and differences between int-2 and other FGFs.

Differential expression of two homologous and clustered oncogenes, Hst1 and Int-2, during differentiation of F9 cells

HST1 (or HSTF1 in human gene nomenclature) transforming gene encodes a novel heparin-binding growth factor which has 40-50% homology with fibroblast growth factors and mouse Int-2 protein. Expression of mouse Hst1 or Int-2 is rare in adult tissues, but both of them are transcribed in embryos. We found that mouse Hst1 and Int-2, like their human counterparts, were located close to each other on the genome: the distance was less than 20 kbp. Hst1 was expressed in an undifferentiated mouse teratocarcinoma cell line, F9. Upon induction of differentiation of F9 cells, the amount of Hst1 transcript was markedly decreased, while that of Int-2 transcripts increased concomitantly.