Overexpression of the c-myc proto-oncogene in colorectal carcinoma is associated with a reduced mortality that is abrogated by point mutation of the p53 tumor suppressor gene

The survival of 119 colorectal cancer patients was analyzed in the light of the overexpression status of the c-myc proto-oncogene mRNA and the point mutation status of the p53 tumor suppressor gene in the primary adenocarcinoma. The presence of >3 fold overexpression of c-myc mRNA in the primary tumor was found to be associated with a better prognosis than patients who evinced no overexpression (P = 0.02, log rank analysis). Point mutation of the p53 tumor suppressor gene was found to be associated with a poorer patient prognosis (P = 0.007, log rank analysis). Endogenous levels of c-myc and point mutation of p53 both contributed independently toward a poorer patient prognosis in Cox regression modeling. The better prognosis seen in patients who overexpress c-myc was offset when c-myc overexpression was coupled with a point mutated p53 gene. These results suggest that in colorectal adenocarcinoma c-myc deregulation leads to increased apoptotic death, but that this response may be modulated by a more downstream event such as point mutation of the p53 gene.     

c-myc copy number gains in bladder cancer detected by fluorescence in situ hybridization

Amplification and overexpression of c-myc have been suggested as prognostic markers in human cancer. To assess the role of c-myc gene copy number alterations in bladder cancer, 87 bladder tumors were examined for c-myc aberrations by fluorescence in situ hybridization. Dual labeling hybridization with a repetitive pericentromeric probe specific for chromosome 8 and a probe for the c-myc locus (at 8q24) was performed to analyze c-myc copy number in relation to chromosome 8 copy number on a cell by cell basis. A clear-cut c-myc amplification (up to 40 to 150 copies per cell) was found in 3 tumors. There was a low level c-myc copy number increase in 32 of the remaining 84 tumors. There was no association of low level c-myc copy number increase with c-myc protein overexpression. This suggests that a c-myc gene copy number gain as detected by fluorescence in situ hybridization does not necessarily reflect a disturbed c-myc gene function but may indicate a structural chromosome 8 abnormality including gain of distal 8q. The strong association of low level c-myc (8q) gains with tumor grade (P < 0.0001), stage (P < 0.0001), chromosome polysomy (P < 0.0001), p53 protein expression (P = 0.0019), p53 deletion (P = 0.0403), and tumor cell proliferation (Ki67 labeling index; P = 0.0021) is consistent with a role of chromosome 8 alterations in bladder cancer progression.     

Overexpression of p53 predicts shorter survival in diffuse type gastric cancer

BACKGROUND: It has been suggested that p53 plays an important part in gastric carcinogenesis but the data remain inconclusive. METHODS: Alteration of the tumour suppressor gene p53 was prospectively investigated by immunohistochemistry in 168 primary gastric cancers. RESULTS: Positive staining, indicative of gene mutations, was detected in 34 tumours (20.2 per cent). No correlation was observed between expression of p53 and various clinicopathological factors, including age, sex, tumour site, gross type, tumour size, depth of invasion, lymph node metastases, distant metastases, and tumour node metastasis stage. However, p53 overexpression was different between intestinal and diffuse type gastric cancer. Survival analysis revealed a significant survival disadvantage of p53 expression in diffuse type gastric cancer (P=0.039) but not in the intestinal type. Multivariate analysis of all 168 patients revealed that independent predictors of recurrent disease included age, invasion depth and nodal involvement but not p53 expression. CONCLUSION: The presence of p53 overexpression may identify a subset of more aggressive tumours with a poor prognosis in diffuse type gastric cancer.     

Expression of amphiregulin, a novel gene of the epidermal growth factor family, in human gastric carcinomas

The expression of mRNA for amphiregulin (AR), a novel gene of the epidermal growth factor family, was examined in 8 human gastric carcinoma cell lines and 32 gastric carcinoma tissues as well as corresponding normal mucosa. Of the 8 gastric carcinoma cell lines, 7 expressed 1.4 kb AR mRNA at various levels. The expression of AR mRNA by TMK-1 and MKN-28 cells was increased by treatment with epidermal growth factor or transforming growth factor a. In surgical cases, all the gastric carcinoma tissues and their adjacent normal mucosa expressed AR mRNA. Interestingly, 20 (62.5%) out of 32 tumors expressed AR mRNA at higher levels than their corresponding normal mucosas (tumor/normal > or = 1.2). No obvious correlation was observed between the AR mRNA levels and the histological types or tumor staging of gastric carcinoma. Immunohistochemically, AR protein was localized to the cytoplasm and/or nucleus in tumor cells. These results suggest that AR produced by tumor cells may be involved in the pathogenesis and/or progression of human gastric carcinoma.     

The influence of carbon source on the level and composition of ceramides of the Candida lipolytica yeast

AIMS AND BACKGROUND: Altered oncogenic activity is a feature associated with many malignant and premalignant conditions. Among the many oncogenes, ras and myc are commonly altered in many tumors. This study aims to evaluate the expression of ras and c-myc oncoproteins in a total of 204 cervical tissue samples, including premalignant and malignant lesions as well as apparently normal cervical tissue. METHODS AND STUDY DESIGN: Mouse monoclonal antibodies against the three mammalian ras gene products (c-H-ras, c-K-ras, c-N-ras) and the c-myc protein were used to evaluate oncoprotein expression by immunocytochemistry. RESULTS: None of the samples analyzed displayed immunoreactivity for H-ras and K-ras. Normal cervical epithelium showed minimal immunoreactivity for N-ras with about 33% of the samples expressing the protein. More conspicuous expression in normal tissue was displayed by c-myc, with about 90% of the samples expressing the protein (mean value of cells positive=34%). The immunoreactivity for N-ras increased with increasing histological abnormality from low-grade squamous intraepithelial lesions (SIL) to invasive carcinoma. Increased immunoreactivity for N-ras was evident in the basaloid cells of malignant lesions, with the maximum value of 66% found in poorly differentiated squamous cell carcinoma (PDSCC). The percentage of nuclei positive for c-myc also showed a gradual increase from low-grade SIL onwards, the highest positivity being found in PDSCC, where the mean value was 85%. Statistical analysis revealed a good correlation between the expression of N-ras (r=0.8922, P=0.001) and c-myc (r=0.8856, P=0.001) and various histological stages of tumor progression in the cervical epithelium. CONCLUSIONS: These results therefore suggest that c-myc and N-ras oncoproteins are important during tumor progression in the uterine cervix.     

Regeneration of transplanted human liver: gene expression at the time of graft implantation

The liver tissue mRNA expression of protooncogenes c-fos, c-myc, c-Ha-ras, c-met and c-erb B1, and TGF alpha and TGF beta genes is sequentially and temporarily increased in the early stages after partial hepatectomy, ischaemia or other mitogenic stimuli. These gene expressions were studied in 38 samples of liver tissue from 24 patients who underwent orthotopic liver transplantation, at different evolution stages. Eleven samples were obtained from surgical liver biopsies before graft implantation at day 0 (Group A), 14 samples from percutaneous liver biopsies during the post-operative period from day 9 to day 48 (Group B) and 13 samples in the long-term follow-up period from day 102 to day 1,382 (Group C). Gene expression was studied using 32P-labeled cDNA and oligonucleotidic probe hybridization in slot blots. A GAPD gene was used as a control gene. All expression values of protooncogenes were related to those of the GAPD gene. After cold ischaema, the relative gene expression (quantity of specific mRNA/quantity of GAPD mRNA ratio) tended to diminish in most cases. The relative expressions of c-fos, c-myc, c-Ha-ras, c-met and TGF alpha gene were correlated at day 0. During and after the liver transplantation, an overexpression of c-fos, c-myc, c-Ha-ras, c-met and TGF alpha was observed in different pathological conditions such as cold ischaemia and conservation injury, acute rejection, and cytomegalovirus infection. In three cases the relative expression values of c-fos, c-myc and c-Ha-ras increased over long-term follow-up without any associated acute pathology. These results suggest the necessity of an intercellular mediation--by means of graft reperfusion--in induction of hepatocyte proliferation and regeneration of the transplanted liver.     

Detection of c-myc translocation in human lung cancer cells by fluorescence in situ hybridization (FISH)

c-myc gene amplification has been found in lung cancer, however, it can not explain all cases of lung cancer with c-myc gene overexpression. Gene translocation is one of the ways by which oncogene is activated. But the old methods for detecting gene mutations are not so effective for the detection of gene translocation, especially in solid tumors. Fluorescence in situ hybridization (FISH) can be used to detect gene translocation more efficiently. Using FISH, we discovered c-myc gene translocation in a lung adenocarcinoma cell line GLC-82 and SV40T-transformed human bronchial epithelial cells. In GLC-82, c-myc gene translocated to the short arm of a C group marker chromosome. In the SV40T-transformed epithelial cells, c-myc gene translocated to 14q32, which was the same as that found in Burkitt's lymphomas. Translocation was related to oncogene activation. c-myc translocation may play an important role in the carcinogenesis of lung cancer.     

Apoptosis-prone phenotype of human colon carcinoma cells with a high level amplification of the c-myc gene

Although apoptosis can be induced by the enforced expression of exogenously introduced c-myc genes, it is not clear whether overexpression resulting from the amplification of the resident c-myc gene in tumor cells is sufficient to induce apoptosis. We have investigated the relationship between c-myc gene amplification and the propensity of tumor cells to undergo apoptosis, using the SW613-12A1 and SW613-B3 cell lines, which are representatives, respectively, of tumorigenic and non-tumorigenic clones isolated from the SW613-S human colon carcinoma cell line. Tumorigenic clones are characterized by a high level of amplification and expression of the c-myc gene, whereas cells of non-tumorigenic clones have a small number of copies and a lower level of expression of this gene. Analysis of c-myc mRNA level in cells cultured under low serum conditions indicated that the expression of the gene is tightly regulated by serum growth factors in non-tumorigenic B3 cells, whereas it is poorly regulated in tumorigenic 12A1 cells, the level of mRNAs remaining relatively high in serum-starved 12A1 cells. Under these conditions, 12A1 cells showed clear evidence of apoptosis, whereas B3 cells were completely refractory to the induction of apoptosis. Moreover, the study of cell lines derived from non-tumorigenic apoptosis-resistant clones following the introduction by transfection of exogenous c-myc gene copies showed that they have acquired an apoptosisprone phenotype. Altogether, our results strongly suggest that deregulated c-myc expression due to high-level amplification confers an apoptosis-prone phenotype to tumor cells. The possible consequences of these observations for cancer therapy are discussed.     

Expression of myc family oncoproteins in small-cell lung-cancer cell lines and xenografts

A number of genes have altered activity in small-cell lung cancer (SCLC), but especially genes of the myc family (c-myc, L-myc and N-myc) are expressed at high levels in SCLC. Most studies have explored expression at the mRNA level, whereas studies of myc family oncoprotein expression are sparse. WE examined the expression of myc proto-oncogenes at the mRNA and protein level in 23 cell lines or xenografts. In the cell lines, the doubling time and the cell-cycle distribution, as determined by flow-cytometric DNA analysis, were examined to establish whether the level of myc-gene-family expression correlated with proliferative parameters. All tumours expressed at least one myc family member at the mRNA level. Exclusive c-myc mRNA expression was demonstrated in 8 tumours, L-myc in 7 and N-myc in I. Five tumours expressed both c-myc and L-myc, and 2 tumours expressed both c-myc and N-myc. In general, the level of expression of c-myc and N-myc was similar at the mRNA and the protein level. Expression of c-myc was positively correlated with the proliferative index (sum of S and G2+M phases) of cell lines, but not with the population doubling time. In general, L-myc-expressing cell lines had a low proliferative index. There was no systematic difference in myc expression between cell lines and xenografts of individual tumours.     

c-myc oncogene expression in estrogen-dependent and -independent breast cancer

We demonstrate that c-myc gene expression is essential for growth of breast cancer cells. It also plays an important role in the progression of human breast cancer. c-myc gene amplification may be important for cancer cell invasion, but perhaps not essential for nodal metastasis. We also provide compelling evidence that the c-myc oncogene is an estrogen target gene in hormone-responsive breast cancer. Hormonal progression of breast cancer could be brought about by the enhanced expression of the c-myc gene, with gene amplification and enhanced c-myc mRNA stability being two major mechanisms involved.     

Immunohistochemical detection of K-sam protein in stomach cancer

The K-sam gene, originally isolated as an amplified gene from the stomach cancer cell line KATO-III, is characterized by its preferential amplification in the undifferentiated type (diffuse type) of stomach cancer and encodes one of the receptors for heparin-binding growth factors or fibroblast growth factors. The K-sam gene has been isolated by different methods and has been designated BEK, TK14, and Cek2. The receptor for keratinocyte growth factor was also found to be encoded by the same gene. To examine the expression of the K-sam protein in stomach cancer, polyclonal antibody pK1-2 was raised against the extracellular domain of the gene product. This antibody detected K-sam proteins by Western blot and flow cytometry analyses in stomach cancer cell lines KATO-III and HSC39, in which the K-sam gene is amplified and overexpressed. By immunohistochemical analysis, 20 of 38 cases of the undifferentiated type of advanced stomach cancer were K-sam positive, whereas none of 11 cases of the differentiated or intestinal type revealed K-sam staining. The K-sam product was observed predominantly in diffusely infiltrative lesions. In one autopsy case, the K-sam protein was detected only focally in the primary tumor, whereas markedly increased staining for the K-sam product was detected diffusely in the metastasized tumor in the lymph node and liver. These results suggest that K-sam overexpression is associated with the malignant phenotype of the undifferentiated type of stomach cancer, such as infiltrative growth and metastasis.     

胃癌组织中HER2基因状态与p21蛋白表达的关系研究

Objective:We aimed to analysis the HER2 gene status and its relationship with p21 protein expression in gastric carcinoma.Methods:Fluorescence in situ hybridisation (FISH) and immunohistochemistry (IHC) techniques were used to detect HER2 gene status and p53 protein in 59 cases of gastric cancer.Results:FISH detection of HER2 gene amplification rate was 16.9% (10/59),HER2 gene amplification in 49 cases without copy number gain and gene amplification were a total of 49.2% (29/59).HER2 protein expression was 42.4% (25/59),HER2 gene amplification rates in patients with +++,++ HER2 protein expression were 3/3 and 5/8,while in patients with + HER2 protein expression,it was 2/14,there was significant difference (P < 0.05).p21 protein expression rate was 49.2% (29/59),HER2 gene amplification rates and p21 protein expression had significant difference in tumor invasion depth,lymph node metastasis (P < 0.05);had no statistical significance in histological type,age,gender differences (P > 0.05).Conclusion:HER2 gene amplification rate and gene copy number had positively correlation with p21 protein expression,HER2 gene status and expression of p21 protein combined detection can provide a reference value in gastric cancer metastasis,patient's condition development and prognosis,it also can guide clinical development of individual treatment.     

Doxorubicin-induced alterations of c-myc and c-jun gene expression in rat glioblastoma cells: role of c-jun in drug resistance and cell death

We studied the effect of doxorubicin on the expression of c-myc and c-jun in the rat glioblastoma cell line C6 and its doxorubicin-resistant variant C6 0.5, at equitoxic exposures. For quantitation, the mRNA levels of these oncogenes were related to those of two domestic genes, beta-actin and glyceraldehyde phosphate dehydrogenase. After a transient overexpression of the genes during the first hour of incubation, there was a selective, dose-dependent down-regulation of both genes by doxorubicin in the sensitive cells. In the resistant cell line, c-myc expression was also decreased in response to doxorubicin incubation, but the expression of c-jun remained unchanged over the whole range of concentrations. In contrast, vincristine had no effect on the amounts of c-myc and c-jun mRNAs in either line. The effect of doxorubicin on the mRNA levels of c-jun was also observed on the JUN proteins by immunoblotting, but the MYC protein levels remained unchanged upon doxorubicin treatment. There was a significant correlation between the levels of c-myc and c-jun gene expression and the degree of growth inhibition induced by doxorubicin. In addition, doxorubicin induced a fragmentation of DNA in sensitive cells, but not in resistant cells, thus revealing a resistance to apoptosis in this line. Doxorubicin-induced cell death did not appear to be mediated by p53 in either cell line.     

Telomerase activity and its clinicopathological significance in gastric cancer

In order to assess the role of telomerase in development of malignant gastric cancer, we measured the telomerase activity in gastric cancer tissues and normal tissues obtained from 95 patients by employing recently developed sensitive PCR (polymerase chain reaction)-based telomerase assay (telomeric repeat amplification protocol, TRAP). We also investigated how telomerase activity related to other clinicopathological findings including DNA ploidy and K-RAS gene point mutation. The telomerase activity was present in 85 of the 95 gastric cancer tissues, whereas we detected no telomerase activity in any normal tissue. The incidence of telomerase activity in gastric cancer tissues was not correlated to age, sex, tumour stage, histological grade, DNA ploidy or K-RAS mutation. Disease-free or overall survival of patients having tumours with detectable telomerase activity was not significantly different from that of those without telomerase activity. These findings suggest that telomerase may play a key role in the establishment and progression of the gastric cancer and further studies will be needed to elucidate the biological role of telomerase in gastric cancer.