Amplification Of C-myc Oncogene Research Articles

Metformin targets c-MYC oncogene to prevent prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related death in American men and many PCa patients develop skeletal metastasis. Current treatment modalities for metastatic PCa are mostly palliative with poor prognosis. Epidemiological studies indicated that patients receiving the diabetic drug metformin have lower PCa risk and better prognosis, suggesting that metformin may have antineoplastic effects. The mechanism by which metformin acts as chemopreventive agent to impede PCa initiation and progression is unknown. The amplification of c-MYC oncogene plays a key role in early prostate epithelia cell transformation and PCa growth. The purpose of this study is to investigate the effect of metformin on c-myc expression and PCa progression. Our results demonstrated that (i) in Hi-Myc mice that display murine prostate neoplasia and highly resemble the progression of human prostate tumors, metformin attenuated the development of prostate intraepithelial neoplasia (PIN, the precancerous lesion of prostate) and PCa lesions. (ii) Metformin reduced c-myc protein levels in vivo and in vitro. In Myc-CaP mouse PCa cells, metformin decreased c-myc protein levels by at least 50%. (iii) Metformin selectively inhibited the growth of PCa cells by stimulating cell cycle arrest and apoptosis without affecting the growth of normal prostatic epithelial cells (RWPE-1). (iv) Reduced PIN formation by metformin was associated with reduced levels of androgen receptor and proliferation marker Ki-67 in Hi-Myc mouse prostate glands. Our novel findings suggest that by downregulating c-myc, metformin can act as a chemopreventive agent to restrict prostatic neoplasia initiation and transformation. Metformin, an old antidiabetes drug, may inhibit prostate intraepithelial neoplasia transforming to cancer lesion via reducing c-MYC, an 'old' overexpressed oncogene. This study explores chemopreventive efficacy of metformin in prostate cancer and its link to cMYC in vitro and in vivo.

P2-06-01: Genomic Instability in Breast Cancers from Atomic Bomb Survivors: An Analysis of Microarray-Comparative Genomic Hybridization with Old Archival Tissues.

Abstract Background: Sixty-six years after two atomic bombs (A-bombs) explosion on Hiroshima and Nagasaki, the incidence of breast cancer in A-bomb survivors still higher than that in controlled populations. We have reported a higher incidence of HER2 and C-MYC oncogene amplification in breast cancers from A-bomb survivors, which suggested genomic instability (GIN) induced by A-bomb radiation exposure might promote breast carcinogenesis in A-bomb survivors. The purpose of this study was to clarify the effect of A-bomb radiation exposure on GIN in breast cancer using microarray-comparative genomic hybridization (aCGH). Materials and Methods: DNA was extracted from the paraffin-embedded tissues of invasive ductal cancers from 11 survivors exposed at 1.5km from the hypocenter and 9 calendar year-matched non-exposed patients followed by aCGH analysis using a high-density oligonucleotide microarray (Agilent® SurePrint G3 8×60k microarray). The total length of chromosomal aberrant region was used as an indicator of GIN, and correlation with clinicopathological factors were statistically tested. Results: The mean of the derivative log ratio spread (DLRSpread), which estimates the log ratio noise by calculating the spread of log ratio differences between consecutive probes along all chromosomes, was 0.60 (range, 0.30 to 1.05). The concordance of aCGH results with FISH results for HER2 gene amplification was 90%. Samples from A-bomb survivors had significantly more copy number aberrations (CNA) than samples from control patients (P= 0.040). Samples with C-MYC gene amplification determined by aCGH analysis tended to harbor more CNA (P= 0.20), and age at the time of diagnosis tended to be inversely associated with the total length of chromosomal aberrant regions (P= 0.13). The multivariate analysis with covariance revealed that the status of A-bomb exposure was the only independent factor which was significantly associated the total length of chromosomal aberrant regions (P= 0.0324). Conclusions: This study suggested that A-bomb radiation may affect the development of chromosomal aberrant regions including oncogene amplification by inducing GIN and may be associated with a higher histological grade in breast cancer found in A-bomb survivors. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-06-01.

Significance of genomic instability in breast cancer in atomic bomb survivors: analysis of microarray-comparative genomic hybridization

BackgroundIt has been postulated that ionizing radiation induces breast cancers among atomic bomb (A-bomb) survivors. We have reported a higher incidence of HER2 and C-MYC oncogene amplification in breast cancers from A-bomb survivors. The purpose of this study was to clarify the effect of A-bomb radiation exposure on genomic instability (GIN), which is an important hallmark of carcinogenesis, in archival formalin-fixed paraffin-embedded (FFPE) tissues of breast cancer by using microarray-comparative genomic hybridization (aCGH).MethodsTumor DNA was extracted from FFPE tissues of invasive ductal cancers from 15 survivors who were exposed at 1.5 km or less from the hypocenter and 13 calendar year-matched non-exposed patients followed by aCGH analysis using a high-density oligonucleotide microarray. The total length of copy number aberrations (CNA) was used as an indicator of GIN, and correlation with clinicopathological factors were statistically tested.ResultsThe mean of the derivative log ratio spread (DLRSpread), which estimates the noise by calculating the spread of log ratio differences between consecutive probes for all chromosomes, was 0.54 (range, 0.26 to 1.05). The concordance of results between aCGH and fluorescence in situ hybridization (FISH) for HER2 gene amplification was 88%. The incidence of HER2 amplification and histological grade was significantly higher in the A-bomb survivors than control group (P = 0.04, respectively). The total length of CNA tended to be larger in the A-bomb survivors (P = 0.15). Correlation analysis of CNA and clinicopathological factors revealed that DLRSpread was negatively correlated with that significantly (P = 0.034, r = -0.40). Multivariate analysis with covariance revealed that the exposure to A-bomb was a significant (P = 0.005) independent factor which was associated with larger total length of CNA of breast cancers.ConclusionsThus, archival FFPE tissues from A-bomb survivors are useful for genome-wide aCGH analysis. Our results suggested that A-bomb radiation may affect the increased amount of CNA as a hallmark of GIN and, subsequently, be associated with a higher histologic grade in breast cancer found in A-bomb survivors.

Incidence of Genomic Aberrations and Associated Efficacy from a Phase III Study Comparing Alemtuzumab (CAMPATH®, MABCAMPATH®) vs Chlorambucil as First Line Therapy for B-Cell Chronic Lymphocytic Leukemia (BCLL).

CAM307 is a randomized Phase III trial comparing the efficacy and safety of alemtuzumab (CAM) with chlorambucil (CHLO). The trial enrolled 297 previously untreated patients (pts) requiring therapy according to NCI-WG criteria. Pts were randomized 1:1 to CAM (n=149) vs CHLO (n=148) using standard dosing regimens. Fluorescence in situ hybridization (FISH) on interphase nuclei of lymphocytes isolated from blood was analyzed for cytogenetic abnormalities prior to the start of therapy. FISH analysis was performed using 13 DNA probes to detect chromosomal aberrations in 17p13.1 (P53), 13q14 (RB1, D13S319 and D13S25), 11q22.3-11q23 (ATM and MLL), 6q27 (subtelomere), 6q21 (chromosome 6q21/alphasatellite 6 cocktail probe), trisomy 8q24 (c-myc), trisomy 12 (CEP12) and translocations involving the locus of immunoglobulin heavy chain gene (IGH, 14q32.33). Samples were analyzed in 282 pts (95%); chromosomal aberrations were detected in 231 pts (82%) while 51 pts (18%) exhibited a normal interphase FISH pattern. The most frequent abnormalities were deletions (del) at loci 13q (49%), sole del 13q (24%), 11q (19%), 17p (7 %), 6q (4 %), and trisomies 12 (14%) and 8q (5%). Translocations IGH, 14q32.33 were detected in 10 pts (4%). An exploratory analysis was performed to correlate time to event variables (assessed by an independent response review panel) with cytogenetics.Overall 165 pts (59%) revealed combination abnormalities. The most frequently observed chromosomal associations were: del 13q + del 14q (N=20, 12%), del 11q + del 13q (N=17, 10%), del 11q + del 13q + del 14q (N=11, 7%), del 11q + del 14q (N=7, 4%), trisomy 12 + del 13q (N=5, 3%), del 13q + del 17p (N=4, 2%), del 11q + trisomy 12 (N=3, 2%) and del 17p + del 6q (N=3, 2%). Coexistence of del 17p and del 11q was not observed. Although del 13q was observed with all chromosome abnormalities, nearly half of the cases del 13q14.3 (D13S25 and D13S319) coincided with an ATM deletion (11q22.3). FISH analysis has allowed the detection of uncommon abnormalities: tetraploidy (n=1), hyperdiploidy (n=1), trisomy 18 (n=1) and c-myc oncogene amplification (>15 copies per nuclei) (n=2). The latter is a well known abnormality in solid tumors but rarely seen in leukemia. In addition, del of the IGH variable region was detected in 70 pts. The biological and clinical significance of this abnormality is to be investigated.Conclusions: Overall, 82% of treatment naïve BCLL pts revealed cytogenetic aberrations and 59% were combination abnormalities. CAM307 demonstrates a significant improvement in PFS in pts treated with CAM vs CHLO who present with del 13q as the sole abnormality; no difference in pts with del 11q. However, a trend towards improved PFS was observed in pts with trisomy 12 and del 17p, which did not reach significance due to small sample size. Further investigation of CAM therapy in high risk cytogenetic subgroups is warranted. [Display omitted]

HER2, TOP2A, CCND1, EGFR and C-MYC oncogene amplification in colorectal cancer

Aim: Recent studies had suggested substantial molecular differences between tumours from different ethnic groups. In this study, the molecular differences between the incidences of colorectal carcinoma in Saudi and Swiss...

C-myc oncogene amplification in ductal carcinoma in situ of the breast.

The c-myc oncogene is frequently activated in invasive breast cancer and has been associated with high nuclear grade, lymph node metastasis and poorer disease outcome. We have examined c-myc oncogene amplification using fluorescence in situ hybridization in a series of 96 pure DCIS. Additionally we assessed amplification and expression of the Her2 and bcl-2 oncogenes. The findings were compared with clinicopathological data, Ki-67 proliferative index and hormone receptor status. We observed c-myc oncogene amplification in 19 tumours (20%). These cases were significantly associated with an average of 38% higher proliferative activity (p = 0.045), a 43% larger tumour size (p = 0.029) and the otherwise rare micropapillary subtype (p = 0.0005). Concluding the c-myc oncogene appears to be involved in the development of a more aggressive phenotype of DCIS.

Amplification of c-myc Oncogene by Chromogenic and Fluorescence In Situ Hybridization in Archival Breast Cancer Tissue Array Samples

Fluorescence in situ hybridization (FISH) is currently considered to be the most specific and sensitive method for detection of oncogene amplifications in human tumor samples. However, FISH requires fluorescence microscopy, which is tedious and does not allow histopathologic evaluation of the cells and tissues examined. Here we compared FISH with the newly developed chromogenic in situ hybridization (CISH), which uses peroxidase enzyme for probe detection instead of fluorescent dyes. CISH was found to be highly concordant with FISH in a tissue array series of 177 archival breast cancer samples. This was true both when comparing CISH with single-color and two-color FISH, the latter including the chromosome 8 centromere probe as reference (the kappa coefficients were 0.67 and 0.76, respectively). Clinicopathologic correlations of c-myc amplification as detected by FISH and CISH were generally the same. By both methods, c-myc amplification was significantly associated with high histologic grade, negative progesterone receptor status, DNA aneuploidy, and high S-phase fraction. c-myc amplification was strongly associated with poor distant metastasis-free survival when amplification was detected by CISH (p = 0.0013), but this association was weaker when FISH was used (p = 0.16 for two-color FISH and p = 0.065 for single-color FISH). These data suggest that CISH is at least as sensitive and specific as FISH in the detection of oncogene amplification in human tumor samples. The possibility for concomitant tissue architecture evaluation using an ordinary transmitted light microscope may favor the use of CISH over FISH in oncogene amplification detection in large tumor series, and tissue arrays and, ultimately, in routine clinical diagnostics.

Determination of c-myc amplification and overexpression in breast cancer patients: evaluation of its prognostic value against c-erbB-2, cathepsin-D and clinicopathological characteristics using univariate and multivariate analysis.

C-myc and c-erbB-2 amplification and/or overexpression as well as total cathepsin-D (CD) concentration have been reported to be associated with poor prognosis in breast cancer. The prognostic significance, however, remains somewhat controversial, partly because of discrepancies among the different methodologies used. We determined the amplification and overexpression of c-myc oncogene in 152 breast cancer patients and examined its prognostic value in relation to c-erbB-2 amplification and overexpression, high concentration of CD (≥ 60 pmol mg–1 protein) and standard clinicopathological prognostic factors of the disease. High CD concentration, as well as c-myc amplification and overexpression, proved to be the best of the new variables examined for prediction of early relapse (ER; before 3 years). After multivariate analysis only CD remained significant, which suggests that the prognostic power of these variables is similar. Using univariate analysis we proved that c-myc amplification and overexpression were highly significant for disease-free survival (DFS) (P = 0.0016 and P = 0.0001 respectively) and overall survival (OS) (P < 0.0001 and P = 0.0095 respectively), although by multivariate analysis c-myc overexpression was statistically significant only for DFS (P = 0.0001) and c-myc amplification only for OS (P = 0.0006). With regard to c-erbB-2, only its overexpression appeared to be significant for DFS and OS, although after multivariate analysis its prognostic power was weaker (P = 0.030 and P = 0.024 respectively). c-myc amplification and overexpression exhibited a tendency for locoregional recurrence (LRR) (P = 0.0024 and P = 0.0075 respectively), however, their prognostic value was lower after multivariate analysis and only CD remained significant. © 1999 Cancer Research Campaign

Correlation between Amplification of c-myc Oncogene and Histophthologic Prognostic Factors in Endomentrial Cancer

Correlation between Amplification of c-myc Oncogene and Histophthologic Prognostic Factors in Endomentrial Cancer

Detection of c-myc oncogene amplification in a CML blastic phase patient with double minute chromosomes

Double minute chromosomes (dmin) are relatively rare in leukemias. Cytogenetic analysis of blood cells from a woman with blastic phase chronic myelogenous leukemia (BC-CML) showed numerous dmin chromosomes and complex abnormalities including a Philadelphia (ph 1)-chromosome. Oncogene amplification in hematopoietic malignancies is also rare. Using PCR, we retrospectively investigated the extent of c-myc gene amplification in DNA extracted from stored blood smears from the patient. To qualify the PCR products, the β-globin gene was used as the internal reference gene and it was co-amplified with the c-myc gene. The extent of amplified c-myc was about 6.8-fold. This finding suggests that the c-myc gene was amplified in dmin and that the gene amplification contributes to the progression to acute leukemia or rapid growth of leukemic cells.

Effects of sex steroids on cell growth and C-myc oncogene expression in LN-CaP and DU-145 prostatic carcinoma cell lines.

The prostate gland is dependent on androgens for the maintenance of its normal growth and functional integrity. Initially, growth of the majority of prostate tumours can be manipulated by endocrine therapy. In the present study, we evaluated the effects of sex steroids on the cell growth and expression of the C-myc oncogene in two human prostatic adenocarcinoma cell lines. We found that dihydrotestosterone increases the proliferation rate of prostatic cells, and amplification of C-myc oncogene is hormone-dependent. We also demonstrated a positive correlation between the number of cells positive for C-myc oncogene and oncoprotein in hormone-treated prostate cell lines.

C-myc oncogene amplification and cytometric DNA ploidy pattern as prognostic factors in musculoskeletal neoplasms.

The relationship between c-myc oncogene amplification in neoplastic cells as determined by means of Southern-blot analysis, and their nuclear DNA content as assessed by combined flow and image cytometry, was investigated in fresh tumor specimens from 33 patients with musculoskeletal neoplasms. Amplification, without rearrangement of the c-myc proto-oncogene, was detected in 4 out of 7 bone sarcomas and in 6 out of 26 soft-tissue sarcomas, but in none of 3 benign giant-cell bone tumors. Among the 10 cases with c-myc amplification, 2 were found to be cytometrically DNA diploid, 2 DNA tetraploid, and 6 DNA aneuploid. Conversely, there were 10 tumors displaying extremely aneuploid DNA patterns without c-myc oncogene amplification. Thus, there was no relationship between c-myc amplification and DNA ploidy; neither did the percentage of S-phase cells, as determined by means of image cytometry, correlate significantly with the occurrence of c-myc amplification. A surprising sex-bias was observed; all 6 cases of c-myc-amplified soft-tissue sarcomas occurred in females, whereas none of the 11 males with such sarcomas showed this amplification. When the clinical follow-up data of the patients were scrutinized, it was found that the DNA ploidy pattern of the neoplastic cell nuclei, in combination with the S-phase values, as well as the occurrence of c-myc amplification, yielded prognostic information, being statistically significant 2 years after the diagnosis.

Clinicopathologic correlations and short-term prognosis in musculoskeletal sarcoma with c-myc oncogene amplification.

The prognostic significance of c-myc oncogene amplification was investigated in a series of 44 patients with musculoskeletal malignancy. There were 21 bone tumors and 23 soft tissue sarcomas. Amplification of the c-myc oncogene was detected in 11 tumors: 4 bone tumors and 7 soft tissue sarcomas. In 9 of the 11 myc-amplified tumors a high grade of malignancy was revealed histologically. The relative frequency of c-myc amplification was higher in grade IV tumors. After a mean follow-up of 18 months, 6 of 11 patients with c-myc-amplified tumors and 12 of 33 patients with nonamplified tumors either exhibited recurrence or died of tumor disease. Both 3-year estimated overall survival and disease-free survival probability were lower for patients with myc-amplified tumors. Amplification of the c-myc oncogene was associated with poor short-term prognosis. Although gene amplification was encountered sporadically in musculoskeletal sarcomas, the reported data suggest that analysis of c-myc may provide valid information on prognosis.

Amplification of the c-myc proto-oncogene in soft tissue sarcomas.

Soft tissue sarcoma fresh specimens from 23 patients were screened for genetic abnormalities of 3 cellular oncogenes, i.e., c-myc and c-myb and c-Ha-ras. Southern blot hybridization analysis demonstrated amplification of the c-myc gene (4- to 8-fold) in 7 cases, i.e., 3 malignant fibrous histiocytomas, 1 liposarcoma, 1 fibrosarcoma, 1 lymphoma of the soft tissues and 1 synovial sarcoma. Amplification of the c-myc gene was not associated to other genetic alterations such as gene rearrangement. Hybridizations with c-myb and c-Ha-ras probes showed no gene abnormalities in this series. Our results indicate that c-myc oncogene amplification may play an important role in the development of certain soft tissue sarcomas as it has been found for other human malignancies. The clinical significance of these features remains to be established.

Oncogene Amplification Detected by in Situ Hybridization in Radiation-Induced Skin Cancers in Rats

Amplification of the c-myc oncogene has been detected by Southern blotting in the DNA of radiation-induced skin cancers in the rat. In the current work the localization of oncogene amplification within specific cells in the different cancers and in multiple biopsies of the same cancer was studied by in situ hybridization. The amount of amplification was measured by counting grains on tissue sections hybridized in situ to biotin-labeled human c-myc third exon, rat v-H-ras, and rat v-Ki-ras probes. The in situ estimates of c-myc amplification were generally correlated with previous findings using the Southern blot method, but within each cancer only a fraction of cells exhibited amplification. Multiple biopsies of a squamous carcinoma showed amplification of v-H-ras and c-myc but not v-Ki-ras during tumor growth, but none of these oncogenes were amplified during tumor regression. The c-myc-positive cells were distributed uniformly within the cancers and exhibited a more uniform nuclear structure in comparison to the more vacuolated c-myc-negative cells. A high [3H]thymidine labeling index was found in irradiated epidermal cells on Day 7 after exposure, and yet no evidence of c-myc oncogene amplification was found in situ. No c-myc amplification was found in unirradiated normal epidermis or in irradiated epidermal cells in the vicinity of radiation-induced cancers. The data indicate that c-myc amplification is cell-specific within radiation-induced carcinomas and does not occur in epidermal cells proliferating in response to radiation exposure.

Nucleolar organiser regions (AgNORS) in anal intraepithelial neoplasia and invasive anal squamous cell carcinoma.

To evaluate the usefulness of counting nucleolar organiser region associated proteins (AgNORs) in the management of anal squamous neoplasia. Using a silver staining technique for NOR associated proteins, 32 routinely processed paraffin wax embedded sections of anal epithelium were assessed. These consisted of normal anal epithelium (n = 9), anal intraepithelial neoplasia (AIN) grades I (n = 5), and III (n = 13), and invasive squamous neoplasia of the anus (n = 5). The median AgNOR counts for every 100 cells are as follows: normal anal epithelium 2.15 (95% CI 1.89-3.94); AIN I 3.21 (95% CI 2.89-7.14); AIN III 4.32 (95% CI 4.00-8.10); and invasive squamous cell carcinoma of the anus 5.51 (95% CI 2.48-10.62). There were significant differences between AgNOR counts in anal cancer and normal epithelium (p < 0.05; Mann-Whitney U test)), AIN III and normal anal epithelium (p < 0.005), and AIN III and AIN I (p < 0.05). No significant differences were observed between AIN I and normal anal epithelium, anal cancer and AIN I, and anal cancer and AIN III. There was a considerable degree of overlap among the different groups. Despite the strong association between AgNOR values and degree of dysplasia, the variability within pathological grade may preclude the adoption of this technique on its own as a prognostic indicator. It may, however, be useful in conjunction with other markers of neoplastic growth such as c-myc oncogene amplification or overexpression as a marker of disease progression in AIN and invasive anal squamous cell cancer.

Epstein-Barr virus (EBV) genomes and c-myc oncogene in oral Burkitt's lymphomas.

In addition to Burkitt's lymphomas, tentative evidence suggests the involvement of Epstein-Barr virus (EBV) in malignant lymphomas of T-cell origin. The c-myc proto-oncogene is strongly associated with the development of lymphoid neoplasias. In the present study, a series of 38 biopsies of oral lymphomas (29 Burkitt's lymphomas, 9 malignant lymphomas of other type) obtained from patients in Tanzania were studied using in situ hybridization (ISH) and polymerase chain reaction (PCR) for detection of EBV DNA and c-myc oncogene. In ISH applied on formalin-fixed, paraffin wax-embedded biopsies, the Bam HI W fragment of EBV DNA was used as the probe. Amplification of c-myc oncogene was studied by PCR with a primer set from Exon II area. As an internal standard beta-globin gene was simultaneously amplified. EBV DNA was disclosed by ISH in five Burkitt's lymphomas only. Using the PCR, 20 of the 29 cases (70%) of Burkitt's lymphomas showed amplification for EBV DNA. Of the other EBV-positive lymphomas, two were of the lymphocytic type (large non-cleaved cell), one histiocytic and one Burkitt's-like lymphoma. All EBV-positive cases found on the agarose gel were positive also with the dot blot, when hybridized with the 32P-labeled EBV Bam HI W-fragment probe. All lymphomas showed similar bands on the gel for c-myc and beta-globin indicating that no amplification of c-myc was present.

Acquisition of tumorigenic potential in the human myoepithelial HBL100 cell line is associated with decreased expression of HLA class I, class II and integrin β3 and increased expression of c‐myc

The human breast cell line HBL100 acquires the capacity to invade normal tissues and to replace them by proliferation in vitro only at high passage levels (HPL). These cells therefore are a useful model for studying tumor progression in vitro. We have analyzed the expression of cell-surface markers supposed to be involved in the control of the neoplastic process. Quantitative flow cytometry has revealed that: (1) spontaneous expression of HLA class-I antigens strongly decreases in HPL HBL100 cells vs. LPL cells, which parallels amplification and over-expression of c-myc oncogene; (2) HLA DR antigens can be induced by IFN-gamma in LPL but not in HPL HBL100 cells; (3) HBL100 cells secrete a soluble protein factor which specifically inhibits HLA DR induction by IFN-gamma even in heterologous cell systems; (4) 50% of LPL HBL100 cells express integrin beta 3, whereas HPL HBL100 cells lose this antigen; (5) this cell line is myoepithelial in origin, since 100% of HBL100 cells exhibit the CD10 antigen. Our data stress a role of HLA antigens, of some integrins and of c-myc in the acquisition of malignant potential by myoepithelial mammary cells of the HBL100 line.

Oncogene Expression Detected by in situ Hybridization in Human Primary Lung Cancer

By means of in situ hybridization using biotinylated oncogene probes and the immunohistochemical reaction of avidin-biotin complex-alkaline phosphatase with substrate, we investigated expression of c-myc oncogene in the formalin-fixed, paraffin-embedded tissue sections from seven patients with squamous cell carcinoma (six cases) and small cell carcinoma (one case) of primary lung origin. The expression of c-myc oncogene was greatly enhanced in all cases studied, with individual and cell-to-cell variation. In contrast, all of the specimens incubated with deoxyribonuclease after the standard pretreatment with ribonuclease T1 were negative for the expression of c-myc oncogene. The in situ hybridization permits estimation of a heterogeneous amplification of c-myc oncogene that may be related to secondary alterations occurring during the progression of the malignant lung tumors.

In vivo amplification and rearrangement of c-myc oncogene in human breast tumors.

We have studied the genomic organization of cellular myc (c-myc) proto-oncogene in 48 human primary breast tumors. Two types of alterations (amplification and rearrangement) were observed in 27 (56%) of the tumors studied. The c-myc proto-oncogene appeared to be amplified 2- to 15-fold in the DNA of 20 tumors (41%). Non-germ line c-myc-related fragments (rearrangements) of variable size were detected in 7 primary breast tumors (6 malignant, 1 benign); 4 of these tumors presented both rearrangement and amplification, and the other 3 presented rearrangement only. The majority of the tumors analyzed were invasive ductal adenocarcinomas; 58% of these showed c-myc locus genetic alterations. Although the c-myc alterations described here do not appear to correlate with the aggressive behavior of primary breast tumors, they seem to be associated with development of breast carcinoma.