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Biomedical subjects

I B Weinstein

Publications and source records attributed to I B Weinstein.

At least 19 recordsLinked to original sources
PubMed1997

Effects of cyclin D1 overexpression on G1 progression-related events.

In previous studies (W. Jiang, S. M. Kahn, P. Zhou, Y. (J. Zhang, A. M. Cacace, A. S. Infance, Y. Doi, R. M. Santella, and I. B. Weinstein 1993, Oncogene 8, 3447-3457) we reported that stable overexpression of cyclin D1 in R6 rat embryo fibroblasts shortens the G1 phase and impairs growth control. In the present study we examined the effects of cyclin D1 overexpression on other events involved in the G1 to S progression, utilizing the overexpressor cell line R6-ccnD1. We found that when compared to R6 control cells, serum-starved quiescent R6-ccnD1 cells had not only increased levels of the cyclin D1 protein but also increased levels of the cyclin E protein. The latter protein was complexed to phosphorylated cyclin-dependent kinase 2 (CDK2). However, in quiescent serum-starved R6-ccnD1 cells this cyclin E-CKD2 complex lacked in vitro kinase activity due to the presence of a heat-stable inhibitory activity, apparently reflecting the inhibitory effects of the CDK inhibitors (CDKIs) p21WAF1 and p27KIP1. Serum stimulation of the quiescent R6-ccnD1 cells was associated with a loss of this inhibitory activity and a decrease in the levels of the latter two proteins, as the cells progressed through the G1 phase. On the other hand, serum stimulation of the control R6 cells was associated with both induction of cyclin E and increased levels of phosphorylated CDK2 proteins and decreased levels of p21WAF1 and p27KIP1, as the cells progressed through the G1 phase. Thus, even though overexpression of cyclin D1 can induce the expression of cyclin E and phosphorylated CDK2, premature activation of cyclin E-CDK2 kinase activity in quiescent cells or during progression through G1 appears to be blocked by CDKIs. Nevertheless, the R6ccnD1 cells have a shorter G1 phase than the control cells presumably due to the high levels of both cyclin D1 and cyclin E. Taken together, these results indicate that overexpression of cyclin D, which is frequently seen in human tumors, can have complex effects on the expression of other genes that control cell cycle progression.

Animals↗
PubMed1997

Antisense to cyclin D1 inhibits the growth and tumorigenicity of human colon cancer cells.

Cyclin D1 plays an important role in regulating the progression of cells through the G1 phase of the cell cycle. This gene is frequently overexpressed in human colon cancer. To address the role of cyclin D1 in growth control and tumorigenesis in this disease, we have overexpressed an antisense cyclin D1 cDNA construct in the human colon cancer cell line SW480E8, which expresses high levels of cyclin D1. The integration and expression of the antisense construct was verified by Southern and Northern blot analyses, respectively, and resulted in decreased expression of the cyclin D1 protein. This was associated with decreased levels of the Rb and p27Kip1 proteins. In addition, the hypophosphorylated form of Rb was increased in these cells. The SW480E8 antisense cyclin D1 cells displayed an increased doubling time, a decrease in saturation density, decreased plating efficiency and anchorage-independent growth, and a loss of tumorigenicity in nude mice. These findings provide direct evidence that increased expression of cyclin D1 in colon tumor cells contributes to their abnormal growth and tumorigenicity. The ability to revert the transformed phenotype of these cells with antisense cyclin D1 suggests that cyclin D1 or its associated cyclin-dependent kinase 4 may be useful targets in the therapy of colon cancer.

Animals↗
PubMed1997

Increased expression of the P27KIP1 protein in human esophageal cancer cell lines that over-express cyclin D1.

In the present study we have characterized eight human esophageal squamous carcinoma cell lines for levels of expression of cyclins D1, E, A and B1; CDKs 1, 2 and 4; the CDK inhibitors p16INK4, p21WAF1 and p27KIP1; the retinoblastoma (Rb) protein; and in vitro CDK2- and CDK4-associated kinase activity; and also compared the growth properties of these cell lines. The level of the cyclin D1 protein varied by over 30-fold amongst the eight cell lines. The high level in two cell lines was associated with amplification of this gene, but in three cell lines it was due to post-transcriptional events. Amongst the eight cell lines there was a significant correlation between the levels of cyclin D1, Rb and p27KIP1 proteins, and CDK4-associated kinase activity. Furthermore, when an exogenous cyclin D1 cDNA was over-expressed in the EC109 cell line by transfection, this led to increased expression of both Rb and p27KIP1. There was, however, no correlation between the level of cyclin D1 expression and the cell doubling times, duration of the G1 phase, or colony-forming efficiency in agar. Two of the cell lines displayed a high level of the cyclin E protein, low levels of cyclin D1, lacked expression of the Rb protein and expressed high levels of the p16INK4 protein. One of these cell lines displayed amplification of the latter gene. There was no correlation between the levels of cyclins E or A and in vitro CDK2 kinase activity, but CDK2 kinase activity was inversely correlated with the duration of the G1 phase of the cell cycle. Taken together, these studies indicate marked heterogeneity in the expression of cell cycle-related proteins amongst a series of esophageal carcinoma cell lines. The correlation between the levels of the cyclin D1, Rb and p27Kip1 proteins suggest the existence of a homeostatic feedback loop between positive and negative acting components of the cell cycle machinery.

Blotting, Northern↗
PubMed1997

Effects of cyclin E overexpression on cell growth and response to transforming growth factor beta depend on cell context and p27Kip1 expression.

Human tumors often display increased expression of cyclin E, suggesting that this might contribute to their abnormal growth. However, we reported recently that overexpression of a human cyclin E cDNA in the nontransformed mouse mammary epithelial cell line HC11 resulted in increased expression of the cell cycle-inhibitory protein p27Kip1 and inhibition of cell growth. To further address the role of cell context, in the present study we analyzed in parallel the effects of cyclin E overexpression in two fibroblast cell lines (Rat1 and NIH3T3) and three nontumorigenic mammary epithelial cell lines (the human cell lines 184B5 and MCF-10F and the mouse cell line HC11). This was associated with increased cyclin E-associated kinase activity in Rat1, NIH3T3, and MCF-10F cells but not in HC11 and 184B5 cells. The derivatives of the latter two cell lines showed increased expression of the p27Kip1 protein and inhibition of cell growth. There was a shortening of the G1 phase in the derivatives of the Rat1 and MCF-10F cells but not in the derivatives of the other three cell lines. Contrary to a previous hypothesis, overexpression of cyclin E was not able to confer anchorage-independent growth in any of these cell lines. However, overexpression of cyclin E was associated with increased resistance to transforming growth factor beta-mediated growth inhibition in the 184B5 and HC11 cells and a decrease in transforming growth factor beta stimulation of the Rat1 and NIH3T3 fibroblasts. Thus, overexpression of the same cyclin E cDNA has cell type-specific effects on various growth parameters. Therefore, additional studies are required to better understand the significance of the frequent increase of cyclin E expression in human tumors.

3T3 Cells↗
PubMed1997

Molecular genetics of small bowel cancer.

Although the molecular genetic changes that take place during carcinogenesis in the large bowel have been well elucidated, very little work has been done on the carcinogenesis process in the small bowel where this phenomenon is much rarer. The few studies that have been done to suggest that certain oncogenes, i.e., erbB2, K-ras, cyclin D1, and p53, are all altered in ways and in frequency similar to these phenomena in large bowel cancer. Some tumor markers have been noted to occur in malignant carcinoid tumours as well. Given the overall similarities in the epidemiology and the role of the adenoma-carcinoma sequence for both small bowel adenocarcinoma and colorectal adenocarcinoma, it is highly likely that the same molecular genetic changes play a major role. Further work is needed to confirm this. If true, a potentially important are of future research would be to determine why these molecular genetic changes occur so much less frequently in the small bowel as compared to the large bowel.

Animals↗
PubMed1996

PKC epsilon functions as an oncogene by enhancing activation of the Raf kinase.

Previous studies have indicated that PKCepsilon behaves as an oncogene when overproduced in rodent fibroblasts (Cacace et al., 1993; Mishak et al., 1993). In the present study, Western blot analysis revealed that the hyperphosphorylated form of Raf kinase was present at a high level in PKCepsilon overproducing R6 rat fibroblasts but not in R6 fibroblasts overproducing PKCalpha or beta1. Extracts from the PKCepsilon overproducing cells also exhibited a marked increase in Raf-1 kinase and MAP-kinase activity. To investigate the significance of these findings, dominant negative mutants of ras (N17) or raf (301-1) were stably expressed in early passage control and PKCepsilon-transformed R6 fibroblasts, by transduction using retrovirus-derived constructs. Dominant negative raf expressing clones exhibited a flat morphology, a decreased saturation density, and decreased growth in soft agar. In addition, these reverted clones exhibited decreased Raf kinase activity. In contrast, dominant negative ras expressing clones remained highly transformed. In addition, PKCepsilon was detected in Raf-1 immunoprecipitates indicating that PKCepsilon forms a complex with Raf-1 in vivo. Taken together, these results suggest that PKCepsilon functions as an oncogene in R6 cells by enhancing activation of the Raf-1 kinase.

Animals↗
PubMed1996

Three-dimensional structure of human protein kinase C interacting protein 1, a member of the HIT family of proteins.

The three-dimensional structure of protein kinase C interacting protein 1 (PKCI-1) has been solved to high resolution by x-ray crystallography using single isomorphous replacement with anomalous scattering. The gene encoding human PKCI-1 was cloned from a cDNA library by using a partial sequence obtained from interactions identified in the yeast two-hybrid system between PKCI-1 and the regulatory domain of protein kinase C-beta. The PKCI-1 protein was expressed in Pichia pastoris as a dimer of two 13.7-kDa polypeptides. PKCI-1 is a member of the HIT family of proteins, shown by sequence identity to be conserved in a broad range of organisms including mycoplasma, plants, and humans. Despite the ubiquity of this protein sequence in nature, no distinct function has been shown for the protein product in vitro or in vivo. The PKCI-1 protomer has an alpha+beta meander fold containing a five-stranded antiparallel sheet and two helices. Two protomers come together to form a 10-stranded antiparallel sheet with extensive contacts between a helix and carboxy terminal amino acids of a protomer with the corresponding amino acids in the other protomer. PKCI-1 has been shown to interact specifically with zinc. The three-dimensional structure has been solved in the presence and absence of zinc and in two crystal forms. The structure of human PKCI-1 provides a model of this family of proteins which suggests a stable fold conserved throughout nature.

Amino Acid Sequence↗
PubMed1996

Increased expression of cyclin D1 and the Rb tumor suppressor gene in c-K-ras transformed rat enterocytes.

Activating mutations in the c-K-ras gene occur in about 40% of human colorectal carcinomas, yet the role of this oncogene in tumorigenesis is not known. We have developed a model cell culture system to study this problem, utilizing the immortalized but non-tumorigenic epithelial cell line IEC18, originally derived from normal rat intestine epithelium. These cells were cotransfected with the drug resistance selectable marker tk-neo and the plasmid pMIKcys, which encodes a mini human c-K-ras gene (15 kb) containing a cysteine mutation at codon 12. Drug resistant clones were isolated. Clones which also expressed the activated c-K-ras gene displayed a transformed morphology, decreased doubling time, increased level of diacylglycerol, anchorage independent growth in soft agar and an aneuploid karyotype and they were also tumorigenic when injected into nude mice. These clones also displayed increased expression, at both the mRNA and protein levels, of cyclin D1 and Rb. These findings may be of clinical relevance since human colorectal tumors also frequently display increased expression of both cyclin D1 and Rb. This model system may be useful for understanding the role and interrelationship between activation of the c-K-ras oncogene and increased expression of cyclin D1 and Rb in colorectal tumorigenesis.

Animals↗
PubMed1996

Linking protein kinase C to the cell cycle: ectopic expression of PKC eta in NIH3T3 cells alters the expression of cyclins and Cdk inhibitors and induces adipogenesis.

Protein kinase C encodes a family of enzymes implicated in cellular differentiation, growth control and tumor promotion. However, very little is known with respect to the molecular mechanisms that link protein kinase C to cell cycle control. Here we report that ectopic expression of PKC eta in NIH3T3 fibroblasts blocks the normal phosphorylation of the Rb protein in quiescent cultures restimulated to enter the cell cycle; PKC eta activates a cellular program that includes increased expression of cyclins E (but not cyclin D), as well as the induced expression of the cyclin-dependent kinase inhibitors p21WAF1 and p27KIP1. The increased expression of the latter inhibitors and their association with the cyclin E-Cdk2 complex results in decreased cyclin E associated kinase activity. Furthermore, in contrast to the control NIH3T3 cells, the cell that express PKC eta can be induced to undergo adipocyte differentiation in response to adipogenic hormones. Thus, PKC eta induces altered expression of several cell cycle related functions, which may contribute to its ability to promote cellular differentiation.

3T3 Cells↗
PubMed1996

Overexpression of cyclin E in the HC11 mouse mammary epithelial cell line is associated with growth inhibition and increased expression of p27(Kip1).

To elucidate the role of cyclin E in cell growth and tumorigenesis in mammary epithelial cells, we have used retrovirus-mediated transduction to generate derivatives of the nontransformed HC11 mouse mammary epithelial cell line that stably express a human cyclin E cDNA (HU4). These derivatives expressed two distinct forms of the exogenous cyclin E protein, which were about M(r) 50,000 and M(r) 42,000, thus corresponding to endogenous cyclin E proteins found in human cells. In contrast to results obtained previously in fibroblasts, overexpression of the HU4 cyclin E cDNA in HC11 cells was associated with an increase in cell size, lengthening of G(1), and inhibition of both anchorage-dependent and independent growth. Furthermore, when quiescent serum-starved cells were restimulated with serum, entry into the S-phase was delayed in the overexpressor cells. Under these conditions, there was also delayed induction in the expression of the endogenous cyclin E protein and in other events involved in the G(1) transition. Despite the high level of expression of the exogenous cyclin E, the derivatives did not display increased cyclin E-associated in vitro kinase activity. The HC11 cells that overexpressed the exogenous cyclin E displayed an increase in the cyclin/cyclin-dependent kinase inhibitor p27(Kip1) in both asynchronous exponentially dividing and synchronous cell populations. These findings indicate that increased expression of this cyclin E cDNA in HC11 cells inhibits rather than stimulates growth and that this may be due to increased expression of the inhibitor p27(Kip1).

Animals↗
PubMed1996

Overexpression of cyclin D1 enhances gene amplification.

Defects in cell cycle control and increased genomic instability, including gene amplification, often occur during cancer development. Cyclin D1 plays a pivotal role in G1, and this gene is frequently amplified and overexpressed in several types of human cancer. This study demonstrates that ectopic overexpression of cyclin D1 in a rat liver epithelial cell line markedly increased the yield of cells containing amplified copies of the CAD gene. This effect was associated with a loss of G1-S checkpoint control, although the cyclin D1-overexpressing cells had a normal p53 gene. The capacity of cyclin D1 to enhance gene amplification may contribute to the process of genomic instability during tumor development.

Animals↗
PubMed1996

Frequent K-ras mutations in small bowel adenocarcinomas.

The reasons for the relatively rare occurrence of small bowel adenocarcinomas when compared to the high frequency of colonic adenocarcinomas are unknown. Activating mutations in the K-ras oncogene occur in about 40% of colonic adenocarcinomas, possibly reflecting the consequences of carcinogenic exposure. To study whether the low incidence of small bowel adenocarcinomas might be due to the absence of activation of cellular oncogenes in small bowel adenocarcinomas, we examined the frequency of K-ras mutations in small bowel adenocarcinomas. K-ras mutations were determined using a polymerase chain reaction (PCR)-based method to detect codon 12 mutations by restriction fragment length polymorphism. PCR amplification was successful in six of nine small bowel adenocarcinoma samples, and revealed point mutations of K-ras at codon 12 in five of these six cases. We conclude that the small bowel might be exposed to carcinogens similar to those responsible for colorectal cancer, but may have developed protective mechanisms against cancer formation.

Adenocarcinoma↗
PubMed1996

Increased expression of cyclin D1 is an early event in multistage colorectal carcinogenesis.

BACKGROUND & AIMS: Cyclin D1 gene amplification and/or overexpression occurs in several human cancers. The level of expression of cyclin D1 protein during the multistage process of human colon carcinogenesis was determined. METHODS: Cyclin D1 protein abundance was determined by immunostaining samples of normal colonic mucosa(n=23), transitional normal mucosa adjacent to adenomas or adenocarcinomas (n=41), hyperplastic polyps (n=8), adenomatous polyps (=35), and adenocarcinomas (n=27), using a polyclonal anti-human cyclin D1 antibody. RESULTS: Cyclin D1 nuclear staining occurred in 30% of adenocarcinomas and 34% of adenomatous polyps but not in hyperplastic polyps or normal or transitional mucosa. Nuclear staining did not correlate with sex, age, size, or dysplasia of the adenomatous polyps or with differentiation and Dukes' staging of the adenocarcinomas. Left-sided colon neoplasms showed nuclear staining more frequently than those right-sided lesions. Diffuse or supranuclear cytoplasmic staining occurred in about one third of hyperplastic polyps, adenomas, and adenocarcinomas and in transitional mucosa adjacent to adenocarcinoma. CONCLUSIONS: Increased nuclear expression of cyclin D1 occurs in around one third of colonic tumors as an early event during multistage process of colon carcinogenesis. Increased expression of cyclin D1 may perturb cell-cycle control in benign adenomas and thereby enhance tumor progression.

Adenocarcinoma↗
PubMed1996

Increased expression of cyclin D1 in a murine mammary epithelial cell line induces p27kip1, inhibits growth, and enhances apoptosis.

Cyclin D1 is frequently amplified and/or overexpressed in human breast cancer and several other types of cancer. To examine the role of cyclin D1 in normal mammary epithelial cells, in the present study we have overexpressed human cyclin D1 in the mouse mammary epithelial cell line HC11, using retrovirus-mediated transduction. We found that the cyclin D1 overexpresser clones displayed a decrease in saturation density, a decrease in anchorage-independent growth, an increased fraction of cells in the G(zero)-G1 phase, and increased expression of beta-casein, when compared to the control cells. The latter finding suggested that they were more differentiated. Furthermore, the cyclin D1 overexpressers displayed a marked increase in susceptibility to induction of apoptosis by serum withdrawal or by treatment with hydroxyurea or the protein kinase C inhibitors CGP 41251 and Ro31-8220. Thus, in some mammary epithelial cells, increased expression of cyclin D1 can inhibit growth, induce differentiation, and enhance apoptosis. These effects might be due, at least in part, to the fact that these derivatives displayed increased expression of the p27kip1 inhibitory protein.

Animals↗
PubMed1996

Increased expression of the cyclin D1 gene in Barrett's esophagus.

Previous studies have found a 3-10-fold amplification and overexpression of the cyclin D1 gene in about 32% of human esophageal squamous cell carcinoma. The purpose of this study was to evaluate the prevalence of increased expression of the cyclin D1 protein in Barrett's esophagus. Using 69 formalin-fixed and paraffin-embedded human esophageal specimens, which had been removed endoscopically or obtained at surgery during 1993 and 1994, all immunohistochemical analyses were performed using an avidin-biotin complex immunoperoxidase technique. Increased nuclear expression of the cyclin D1 protein was noted in 32 of 69 samples (46%; 44% of the samples from males and 50% of the samples from females). Positive nuclear staining for the cyclin D1 protein in Barrett's disease with intestinal metaplasia was found in 38% of the male cases and 25% of the female cases, whereas in gastric metaplasia it was positive in 33% of men and 48% of women. Nuclear accumulation of the cyclin D1 protein was also found in both dysplastic and nondysplastic lesions, and it was not associated with sex, age, or cigarette or alcohol consumption. Samples from patients taking proton pump inhibitors tended to be less frequently positive (32%) for cyclin D1 nuclear staining when compared to patients taking H2 antagonists (45%) or antacids (55%). These studies suggest that increased expression of cyclin D1 is an early event in the tumorigenic process of esophageal adenocarcinomas and that the increased expression of this gene might predispose the epithelium to malignant transformation.

Adenocarcinoma↗
PubMed1996

Relevance of cyclin D1 and other molecular markers to cancer chemoprevention.

Until recently studies on mutations in cellular genes implicated in multistage carcinogenesis have concentrated mainly on dominant acting mutations in cellular proto-oncogenes, genes that normally mediate agonist-induced signal transduction pathways, and recessive mutations in cellular tumor suppressor genes, whose normal products appear to inhibit cell growth and/or control differentiation and cell-cell interactions. It seems likely, however, that a third category of cellular genes, the cyclins and cyclin-related genes, may also be critical targets during multistage carcinogenesis because of the central role that they play in controlling cell cycle progression. These proteins could, therefore, provide biomarkers for identifying individuals at high risk of developing cancer and also serve as novel targets for chemopreventive agents. This paper reviews evidence that the gene cyclin D1 is amplified and/or overexpressed in a major fraction of human tumors, and that this can occur relatively early in the carcinogenic process. Mechanistic studies indicates that this overexpression plays a critical role in tumor progression as well as the maintenance of the tumorigenic phenotype. Thus, increased cyclin D1 expression can enhance gene amplification and cell transformation and antisense to cyclin D1 can revert malignant cells. The latter findings provide direct evidence that cyclin D and related proteins might be useful markers and also targets for cancer chemoprevention.

Anticarcinogenic Agents↗
PubMed1995

Antisense to cyclin D1 inhibits growth and reverses the transformed phenotype of human esophageal cancer cells.

The cyclin D1 gene is amplified and overexpressed in a significant fraction of human esophageal tumors, and several other types of human cancer, but the functional significance of this overexpression has not been established. To further address the roles of cyclin D1 in growth control and tumorigenesis, we have overexpressed an antisense cyclin D1 cDNA construct, either constitutively or inducibly, in the HCE7 human esophageal cancer cell line in which cyclin D1 is amplified and expressed at high levels. The expression of antisense cyclin D1 led to decreased expression of cyclin D1 at both mRNA and protein levels, and this was associated with a marked inhibition of cell proliferation. Antisense cyclin D1 expressing cells displayed a decreased plating efficiency, increased doubling time, decreased saturation density, increased cell size, decreased cyclin D1-associated in vitro kinase activity, decreased anchorage-independent growth, and a loss of tumorigenicity in nude mice. These findings provide direct evidence that the overexpression of cyclin D1 in certain tumor cells contributes to their abnormal growth and tumorigenicity. The ability to revert the transformed phenotype of these cells with antisense cyclin D1 suggests that cyclin D1 may be a useful target in cancer therapy.

Cell Adhesion↗