myc family gene abnormality in lung cancers and its relation to xenotransplantability

In order to study the relationship between tumor transplantability to the nude mouse and abnormality of the myc family genes (c-myc, N-myc, L-myc) in human primary lung cancers, 32 various lung cancers were analyzed for abnormality of the myc family genes by Southern blot hybridization, and were transplanted s.c. into nude mice. Southern blot analysis showed that four non-small cell carcinomas and three small cell carcinomas had amplified c-myc and L-myc genes, respectively. Allelic deletion of the L-myc gene was observed in seven cancers, of which two also had an additional band of the c-myc gene or amplification of the L-myc gene. No abnormality of the N-myc gene was observed in this series. Of 13 cancers with abnormality of the myc family genes, 11, including all tumors with myc gene amplification, were transplantable to nude mice. Of 19 tumors without any abnormalities of the myc family genes, however, only five were transplantable to nude mice (P less than 0.005). These results indicate that abnormality of the myc family genes, especially gene amplification, might promote tumorigenic ability in xenotransplantation of lung cancers and this phenomenon might be closely related to the function of the myc gene.     

Activation of myc gene family in human lung carcinomas and during heterotransplantation into nude mice.

myc gene family activation (c-myc, L-myc, and N-myc) was examined in 26 human lung carcinomas and in their corresponding xenografts in nude mice. Of the 16 neuroendocrine (NE) carcinomas studied, amplification was observed in 4 with a c-myc probe and in 1 with both L- and N-myc probes. Overexpression was found in 1 of 7 cases studied for c-myc mRNA, in 1 of 7 cases for N-myc, and in 2 of 7 cases for L-myc. Of the 10 non-small cell lung carcinomas studied, only c-myc was amplified in 1 case and overexpressed in 5 of 7 cases. These results suggest that L- and N-myc gene activation are restricted to NE carcinomas. Over-expression of the myc gene without amplification was detected in 36% of cases. During heterotransplantation, there was a 27% change in myc gene abnormality and a 57% increase in myc expression levels, mostly in NE carcinomas (5 of 7; 71%). In a total of 42 xenografted lung carcinomas studied, 45% amplification and 77% overexpression of one of the myc genes were detected with a high prevalence of L-myc overexpression in NE carcinomas (50%) and of c-myc overexpression in non-small cell lung carcinomas (66%). Finally, 19 of 26 (73%) tumors are growing in nude mice with no myc gene amplification and 43% with no myc mRNA overexpression. Thus myc gene activation is not strictly required for heterotransplantation but seems to be a favorable factor in the maintenance and progression of lung carcinomas in vivo.     

Heterogeneity of lung cancer cells with respect to the amplification and rearrangement of myc family oncogenes

Seventy lung tumors from 53 patients were analysed for alterations of myc family oncogenes, c-myc, N-myc and L-myc, to evaluate when activation of these genes occurs during tumor development. The 53 cases were 17 small cell carcinomas (SCCs), 18 adenocarcinomas, 12 squamous cell carcinomas (SqCs), 4 large cell carcinomas and 2 adenosquamous carcinomas. Either N-myc or L-myc was amplified in 4 of the 17 (one N-myc and 3 L-myc) SCCs (24%), while c-myc was amplified in 3 of the 12 SqCs (25%). In one SCC, amplification of N-myc was found in the primary tumor, a pulmonary hilar lymph node metastasis and a pleural metastasis, but not in a liver metastasis or a para-aortic lymph node metastasis. In one SqC, c-myc was amplified in a pleural metastasis and a lymph node metastasis, but not in the primary tumor. In 2 cases of SCCs, amplification or rearrangement of c-myc was detected only in the cell lines, but not in the original tumors taken from the same individuals. These results indicate that tumor cells were heterogeneous for amplification and rearrangement of myc family oncogenes, and suggest that activation of these oncogenes in SCCs and SqCs occurs not at the time of malignant transformation but during tumor progression.     

Coamplification of the L-myc and N-myc oncogenes in a neuroblastoma cell line

The L-myc, N-myc and c-myc genes are members of the myc oncogene family. In particular, L-myc is novel, and amplification of L-myc is still unknown except in small cell lung carcinoma. We examined L-myc amplification in 30 human neuroblastomas using Southern blot hybridization, and found that the L-myc gene was amplified approximately 5-fold in GOTO, a human neuroblastoma cell line. The N-myc gene was also amplified approximately 60-fold and furthermore, over-expression of L-myc and N-myc genes was observed in this cell line. In this report, we describe the coamplification of the myc gene family in the GOTO neuroblastoma cell line.     

Analysis of the activation of the myc family oncogene and of its stability over time in xenografted human lung carcinomas

In order to validate the use of the nude mouse as a model for studying lung cancers, 21 different lung cancers were xenografted onto nude mice and the tumoral DNA and RNA were analyzed for abnormality in the myc family genes (c-myc, L-myc, and N-myc). Six of 14 small cell lung cancers (SCLC) showed a 4-35-fold amplification for L-myc, 5 of 7 non-SCLC a 3-5-fold amplification for c-myc, and 1 of 14 SCLC an 80-fold amplification for N-myc. Of the 7 SCLC with amplified L- or N-myc oncogenes, 4 were of the small and large histological type, while only 5 of the 21 cases studied were of the small and large type. All xenografted tumors with amplification of one of the myc genes showed overexpression of the related mRNA. Overexpression without amplification of the myc genes was observed for 3 SCLC and 2 non-SCLC. These results indicate that the L-myc gene seems to be associated with the small and large phenotype in SCLC, whereas c-myc seems to be implicated in non-SCLC. Of the 21 lung cancers studied 14 were analyzed for myc family gene activation for serial passages into nude mice. No variation of DNA amplification was observed during long-term growth in nude mice for any of the myc oncogenes. Changes in the level of mRNA expression were observed only for c-myc; a beginning of expression in one SCLC and an increase in expression in one non-SCLC were noted in late passages when compared with early ones. The nude mouse is therefore a valuable model for the study of lung cancers "over a 4-year period at least."     

Heterogenous amplification of myc family oncogenes in small cell lung carcinoma

One hundred forty-two foci of small cell lung carcinoma (SCLC) from 47 patients were examined for amplification of myc family oncogenes (c-myc, N-myc, and L-myc), by dot blot hybridization using formalin-fixed and paraffin-embedded materials which were resected surgically or obtained at autopsy. Some selected patients were also examined by in situ hybridization. Amplification of myc family genes was detected in 11 patients (23.4%) (c-myc in one, N-myc in five, and L-myc in five). Two of the 11 patients (one with N-myc and one with L-myc) had heterogenously amplified clones. In the patient with N-myc amplification, amplification was detected in metastatic tumors in the pancreas, lung, and pleura, but not in the liver and lymph node metastases. In the primary tumor, areas with and without N-myc amplification were seen. In the patient with L-myc amplification, although amplification was not detected in the surgically resected primary lesion, mediastinal lymph node metastatic lesions obtained at autopsy showed L-myc gene amplification. These two cases, together with previously reported evidence, suggest that myc gene amplification plays an important role in malignant progression, rather than development, of SCLC. In Stage III and IV groups, patients with over ten-fold myc gene amplification were suggested to survive for a shorter time than patients without such amplification (P = 0.06).     

myc family DNA amplification in small cell lung cancer patients' tumors and corresponding cell lines

Tumor specimens procured from 38 different small cell lung cancer patients were studied for DNA amplification of the myc family of protooncogenes (c-myc, N-myc, and L-myc). Six of the 38 specimens (16%) had 4-fold or greater myc family DNA amplification (N-myc in 4 and L-myc in 2). All 6 tumors with amplification came from patients who had received combination chemotherapy. The myc family gene copy number of the DNA prepared from 9 tumor cell lines established from these 38 patients was similar to the myc family gene copy number in the DNA prepared from fresh tumor specimens from these same patients. myc family DNA amplification is present in 16% of small cell lung cancer patients' tumors and the amplification pattern in the tumor cell lines is representative of the fresh tumors obtained from the same patients.     

Gene copy numbers of erbB oncogenes in human pheochromocytoma

ErbB-1, -2, -3 and -4 proteins are growth factor receptors, encoded by the family of respective erbB protooncogenes. These receptor-encoding proto-oncogenes frequently undergo amplification, and less frequently, a deletion, in several human neoplasms. The role of the ErbB family in human endocrine neoplasms, including pheochromocytoma (PHEO), was not extensively tested and not previously established. The expression/overexpression of erbB oncogenes in pheochromocytoma tissue was determined only in a few cases, and to the best of our knowledge, their mutations (amplification or deletion) were not examined in any series of PHEO cases. We, therefore, used a double differential polymerase chain reaction (ddPCR) for determination of the amplification/deletion profiles of erbB-1, -2, -3 and -4 genes in formalin-fixed, paraffin embedded (FFPE) specimens of human PHEOs. We examined the average gene copy number (AGCN) of the genes in 36 samples of pheochromocytomas (2 extra-adrenal and 34 adrenal tumors). We found the mean AGCNs of the oncogenes equal 1.18 for erbB-1 [amplification was found in 11/35 cases (31%) and deletion in 6/35 cases (17%)], 2.00 for erbB-2 [amplification was found in 8/34 cases (24%), no deletion was found], 1.36 for erbB-3 [amplification was found in 4/36 cases (11%) and deletion in 1/36 cases (3%)], and 1.22 for erbB-4 [amplification was found in 5/30 cases (17%) and deletion in 1/30 cases (3%)]. A mutation(s) of any erbB oncogene was found in 25/36 (69%) samples tested. Some abnormalities of the erbB oncogenes showed interesting correlations with one another and with clinical features of the tumors. The frequent occurrence of amplifications and deletions of the erbB oncogenes in human pheochromocytoma implies the importance of the gene family in the development of these tumors.     

Cellular protoonocogenes are infrequently amplified in untreated non-small cell lung cancer

To examine a potential contribution of protooncogene abnormalities other than point-mutational activation of the K-ras protooncogene in the classification of non-small cell lung cancer, amplification of cellular protooncogenes was studied in 47 lung tumour specimens obtained at thoracotomy and in four lung tumour cell lines. The primary tumours included 21 adenocarcinomas, nine large-cell carcinomas, 13 epidermoid carcinomas, one carcinoid and three metastases of primaries outside the lung. The copy numbers per haploid genome of 11 protooncogenes in every tumour sample were determined: H-ras, K-ras, N-ras, c-myc, N-myc, L-myc, erbB, mos, myb, ncu (erbB-2) and ral amplifications. The c-myc gene was amplified 5-7-fold in two adenocarcinomas, the H-ras gene 3 5-fold in one adenocarcinoma, while the K-ras and the neu gene were amplified in lung metastases from a colorectal and a breast cancer primary respectively. None of the tumours with an amplified protooncogene simultaneously harboured a mutationally activated K-ras gene. We conclude that amplification of the investigated protooncogenes is a rare event in non-small cell lung cancer. In view of the two c-myc amplifications detected, a systematic study of c-myc expression levels in non-small cell lung cancers appears worthwhile.     

myc family DNA amplification in tumors and tumor cell lines from patients with small-cell lung cancer.

The myc family DNA copy number of 291 specimens (183 tumors and 108 tumor cell lines) from patients with small-cell lung cancer has been reported in 15 different studies. Thirty-five of 108 (32%) cell lines from small-cell lung cancer patients have myc family DNA amplification (16 c-myc, 7 N-myc, and 12 L-myc). Thirty-seven of 183 (20%) tumors from patients with small-cell lung cancer have myc family DNA amplification (3 c-myc, 13 N-myc, and 18 L-myc). The myc family DNA copy number in tumors from patients with small-cell lung cancer is similar in the majority of sites from the same patient. The presence of myc family DNA amplification in the tumor cell line is also typically present in the tumor from the same patient. myc family DNA amplification is present in a minority of patients with small-cell lung cancer, and the data on its association with shorter survival of patients are meager at present. Future studies on the biology of the myc family in small-cell lung cancer may require use of newer technologies that can work with small tissue samples typically available at the start of therapy.     

Oncogene amplification in squamous cell carcinoma of the oral cavity

We have determined the prevalence of amplification of c-myc, N-myc, L-myc, H-ras, Ki-ras, and N-ras oncogenes in 23 cases of squamous cell carcinoma of the oral cavity, using Southern hybridization analysis of DNA extracted from the primary tumor tissues. Nick-translated oncogene probes and oncogene inserts labeled to high specific activities were used. We observed a 5- to 10-fold amplification of one or more of c-myc, N-myc, Ki-ras and N-ras oncogenes in 56% of the tumor tissue samples, with these oncogenes not being amplified in the peripheral blood cells of the same patients. L-myc and H-ras were not amplified in any of our samples. The oncogene amplifications seemed to be associated with advanced stages of squamous cell carcinomas, with the ras and myc family oncogenes being amplified in stages 3 and 4. Hybridization with N-myc detected an additional 2.3 kb EcoRI fragment, along with the normal 2.1 kb fragment. Our data also demonstrated amplification of multiple oncogenes in the same tumor tissue sample. About 60% of the samples with amplified oncogenes showed simultaneous amplification of 2 or more oncogenes. The results showing different oncogene amplifications in similar tumors, as well as multiple oncogene amplifications in the same tumor, suggest that these oncogenes may be alternatively or simultaneously activated in oral carcinogenesis.     

Oncogene Amplification in Squamous Cell Carcinoma of the Oral Cavity

We have determined the prevalence of amplification of c- myc , N- myc , L- myc , H- ras , Ki- ras , and N- ras oncogenes in 23 cases of squamous cell carcinoma of the oral cavity, using Southern hybridization analysis of DNA extracted from the primary tumor tissues. Nick-translated oncogene probes and oncogene inserts labeled to high specific activities were used. We observed a 5- to 10-fold amplification of one or more of c- myc , N- myc , Ki- ras and N- ras oncogenes in 56% of the tumor tissue samples, with these oncogenes not being amplified in the peripheral blood cells of the same patients, L- myc and H- ras were not amplified in any of our samples. The oncogene amplifications seemed to be associated with advanced stages of squamous cell carcinomas, with the ras and myc family oncogenes being amplified in stages 3 and 4. Hybridization with N- myc detected an additional 2.3 kb Eco RI fragment, along with the normal 2.1 kb fragment. Our data also demonstrated amplification of multiple oncogenes in the same tumor tissue sample. About 60% of the samples with amplified oncogenes showed simultaneous amplification of 2 or more oncogenes. The results showing different oncogene amplifications in similar tumors, as well as multiple oncogene amplifications in the same tumor, suggest that these oncogenes may be alternatively or simultaneously activated in oral carcinogenesis.     

Expression and amplification of myc gene family in small cell lung cancer and its relation to biological characteristics

Eighteen small cell lung cancer (SCLC) lines (including nine lines established by this group) as well as 31 tumor samples from 23 SCLC patients were examined for the surface antigen phenotype and the expression and amplification of the myc gene family. The expression of NE-150 neuroendocrine, PE-35 panepithelial and OE-130 epithelial antigens corresponded well with the level of biomarkers of SCLC lines, i.e., the NE-150+/PE-35+/OE-130- phenotype corresponded to classic type, while the other phenotypes such as NE-150+/PE-35-/OE-130- to variant type. In tumor specimens, most classic SCLC (consisting of oat cell type and intermediate cell type, subtype a) showed NE-150+/PE-35+/OE-130- phenotype, while small cell-large cell carcinoma (intermediate cell type, subtype b) expressed various phenotypes. The amplification of the myc gene family was observed in nine out of 18 lines (50%) and five out of 23 patient tumors (22%). Higher levels of expression of either c-myc, N-myc, or L-myc were detected in 16 out of 18 lines (89%) and in five out of six patient tumors (83%), when compared with that of normal or fetal lung tissues. Thus, the higher expression without obvious myc gene amplification was observed. The cell lines and tumors with the amplified myc always expressed their corresponding myc genes. The results suggested that higher levels of expression of the myc gene family may play a significant role in the oncogenesis of SCLC. Amplification and/or high levels of expression of c-myc were observed not only in variant type SCLC lines, but also in classic type lines. Thus, they were not necessarily associated with distinct biomarkers of SCLC lines.     

Gene Amplification of int-2 and erbβ in Human Esophageal Cancer: Relationship to Clinicopathological Variables

Gene amplification is a relatively frequent event in human malignant tumors and is believed to play an important role in tumor progression. The int-2 and erbB genes are amplified more frequently than any other genes in human esophageal cancer. In order to investigate the correlation between these two proto-oncogenes and the clinical behavior of esophageal cancer, we examined DNA amplification of int-2 and erbB and analyzed their relationship to clinicopathological variables. Genomic DNA was extracted from 21 esophageal squamous carcinomas and normal esopfiageal mucosa, as well as from 4 metastatic tumors. We used Southern blot analysis for detection of gene amplification. Amplification of int-2 was observed in 13 of 21 cases (62%) and in all the metastatic tumors (4/4; 100%). We found a significant correlation between amplification of int-2 and the length of the primary lesion. Amplification of erbB was detected in 3 of 18 patients (17%). All patients who showed amplification of erbB also demonstrated amplification of int-2. These results suggest that amplification of int-2 or neighboring genes on 11q may participate in tumor progression and metastasis in patients with esophageal squamous cancer.     

Oncogene amplification in pediatric brain tumors

Despite a considerable amount of information concerning chromosomal and molecular abnormalities found in gliomas in adults, relatively little is known regarding these abnormalities in pediatric brain tumors. We have analyzed DNA from 37 primary brain tumors and 4 tumor-derived cell lines for oncogene amplification. Probes utilized represent 11 known oncogenes (erbB1, gli, neu, myc, L-myc, N-myc, H-ras, K-ras, N-ras, sis, and src). Of 20 primary medulloblastomas studied, only one tumor was found to have erbB1 amplification. In contrast, of the 4 medulloblastoma cell lines studied, 1 had c-myc amplification, 1 had erbB1 amplification, and 1 had amplification of N-myc. Twelve glial brain tumors were analyzed, and only 1 case with amplification of the erbB1 oncogene was found. Other tumors studied include 1 meningioma, 2 ependymomas, 1 anaplastic ependymoma, and 1 cerebral primitive neuroectodermal tumor, none of which had oncogene amplification. These results suggest that oncogene amplification is relatively uncommon in primary medulloblastomas, but the frequency and diversity of oncogene amplification is greater in tumors that can be established as cell lines. The lower frequency of erbB1 amplification in glial brain tumors in children compared to adults is consistent with the generally lower grade of glial tumor histology seen in pediatric patients. However, the case with amplification of the erbB1 oncogene represented 1 of 2 cases of glioblastoma multiforme we studied, which suggests that pediatric glioblastoma multiforme may have a similar frequency of erbB1 oncogene amplification to glioblastomas seen in adults. Our results suggest that oncogene amplification is a relatively uncommon mechanism of oncogene activation in pediatric brain tumors, and they provide molecular evidence for heterogeneity in tumors classified as medulloblastomas.     

Coamplification of the L-myc and N-myc Oncogenes in a Neuroblastoma Cell Line

The L- myc , N- myc and c- myc genes are members of the myc oncogene family. In particular, L- myc is novel, and amplification of L- tnyc is still unknown except in small cell lung carcinoma. We examined L- myc amplification in 30 human neuroblastomas using Southern blot hybridization, and found that the L- myc gene was amplified approximately 5-fold in GOTO, a human neuroblastoma cell line. The N- myc gene was also amplified approximately 60-fold and furthermore, over-expression of L- myc and N- myc genes was observed in this cell line. In this report, we describe the coampliflcation of the myc gene family in the GOTO neuroblastoma cell line.     

Establishment of a human malignant meningioma cell line with amplified c-myc oncogene

A new cell line (KT21-MG1) has been established from a human malignant meningioma transplanted into nude mice. The cultured cells showed epithelial cell-like morphology and were positive immunohistochemically for vimentin as the original tumor. They have been grown continuously in vitro for more than 2 years. The population doubling time was about 24 hours at the 30th passage. The cells are capable of proliferating in soft agar medium and produced tumors in nude mice, the histologies of which were similar to the original patient-derived tumor. Analysis of cellular oncogenes showed that myc and fps were amplified approximately tenfold and threefold, respectively, in this cell line, whereas N-myc, L-myc, N-ras, K-ras, H-ras, abl, erbB2, Blym, src, raf-1, myb, and sis were not changed significantly. The amplification of myc was accompanied by an enhanced expression. Chromosome studies of cultured cells showed the monosomy of chromosome 22 that has been reported to be a specific abnormality in meningiomas.     

Overexpression of erbB-2 or EGF receptor proteins present in early stage mammary carcinoma is detected simultaneously in matched primary tumors and regional metastases

Membrane protein levels of erbB-2 and epidermal growth factor (EGF) receptor as well as gene aberrations affecting these proto-oncogenes in human mammary cancer were determined in primary and metastatic lesions. Among 57 patients erbB-2 gene amplification was detected in 11 tumors (19%). In 10 of these patients where expression levels could be assayed gene amplification was associated with a high level of erbB-2 protein. In contrast, EGF receptor gene amplification with over-expression of the protein product was observed in 2 tumors (4%). In addition, 14 out of 53 (26%) primary tumors exhibited moderately increased erbB-2 protein levels in the absence of gene amplification. Similar aberrations resulting in overexpression of EGF receptor protein without detectable gene amplification were associated with 2 tumors (4%) among 47 patients analyzed. In 7 patients, expression level and gene copy numbers of erbB-2 or EGF receptor were similarly altered in the primary tumor and metastatic lesions derived from the same patient. Concordance of increased receptor gene expression in primary and metastatic lesions combined with the observation that such alterations are detectable as early as stage I and II mammary tumors, suggests that overexpression of erbB protooncogene family members can develop early in breast cancer and is maintained during tumor progression. Comparison of erbB-2 overexpression with clinical disease parameters revealed a correlation of this alteration with inflammatory mammary carcinoma (P = 0.042) implying an association of elevated erbB-2 protein levels with enhanced malignancy of the tumor cell in vivo.