[Cancer Research 62, 4562-4565, August 15, 2002]
© 2002 American Association for Cancer Research
Cyclin D1 Is Not an Essential Target of ß-Catenin Signaling During Intestinal Tumorigenesis, but It May Act as a Modifier of Disease Severity in Multiple Intestinal Neoplasia (Min) Mice1
Jenny Wilding,
Josef Straub,
Julie Bee,
Michael Churchman,
Walter Bodmer,
Clive Dickson,
Ian Tomlinson and
Mohammad Ilyas2
Cancer and Immunogenetics Laboratory, Cancer Research UK, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford OX3 9DS, United Kingdom [J. W., W. B.]; Bayer AG, D-42096 Wuppertal, Germany [J. S.]; Biological Resources [J. B.], Viral Carcinogenesis Laboratory [C. D.], and Molecular and Population Genetics Laboratory [I. T.], Cancer Research UK, London WC2A 3PX, United Kingdom; and Oxford Molecular Pathology Group, Level 3, The Women’s Centre, John Radcliffe Hospital, Headington, Oxford OX3 9DU, United Kingdom [M. C., M. I.]
 |
ABSTRACT
|
|---|
Deregulation of ß-catenin activity is an important step in the development of colorectal cancers. One consequence of this is transcriptional activation of cyclin D1, an oncogene known to be overexpressed in colorectal cancers. We tested the hypothesis that cyclin D1 gene activation is important for intestinal tumorigenesis. Multiple intestinal neoplasia mice (a model for human familial adenomatous polyposis) were crossed with cyclin D1 knockout (Ccnd1-/-) mice. Despite the absence of cyclin D1, intestinal tumors still developed. However, Ccnd1-/- multiple intestinal neoplasia mice developed significantly fewer tumors than Ccnd1+/- or Ccnd1+/+ mice (P = 0.003). We conclude that cyclin D1 is not essential for intestinal tumorigenesis, but it may act as a modifier gene.
|
Introduction
|
|---|
One of the first events in the development of CRC3
is mutation of the APC gene (1)
. Individuals carrying a germ-line mutation of this gene develop a condition called familial adenomatous polyposis and are prone to the development of hundreds to thousands of colorectal tumors. In addition, APC gene mutations are found in up to 80% of sporadic CRCs. Tumors usually show biallelic inactivation of APC, which results in an increase in the level and activity of ß-catenin. The importance of deregulated ß-catenin activity in intestinal tumorigenesis is underscored by the fact that of those CRCs that are wild-type for APC, up to 50% carry gain of function mutations of the ß-catenin gene (2, 3, 4)
. ß-Catenin has numerous functions including control of cell adhesion and Wnt signaling. In fulfilling the latter of these roles, it can complex in the nucleus with LEF/TCF transcription factors to induce transcriptional activation of a large number of target genes. It is uncertain which of these target genes are most important in transducing the oncogenic activity of ß-catenin. One candidate is cyclin D1 (CCND1), a gene that drives the transition from G1 to S phase during the cell cycle. CCND1 is a known oncogene in both epithelial (5)
and mesenchymal (6)
cancers, where translocation, amplification, or message stabilization results in increased protein expression. It may represent a critical target because it is known to be specifically induced by ß-catenin (7)
, and although CCND1 mutations have not been identified in CRCs, increased cyclin D1 expression is reported as an early event in colorectal tumorigenesis (8)
. In this study, we sought to ascertain the importance of cyclin D1 during intestinal tumor development. Cyclin D1 knockout mice (Ccnd1-/-; Ref. 9
) were crossed with Min mice (10)
. Min mice, which carry a germ-line Apc mutation, develop numerous intestinal tumors and are generally regarded as a model for human familial adenomatous polyposis. Min mice with three different cyclin D1 genotypes were produced (i.e., Ccnd1+/+; Apcmin/+ / Ccnd1+/-; Apcmin/+ / Ccnd1-/-; Apcmin/+) and examined for intestinal tumor development.
|
Materials and Methods
|
|---|
Mouse Breeding.
All animals were housed and bred in the animal facilities of Cancer Research UK at Clare Hall Laboratories (South Mimms, London, United Kingdom). Experiments were conducted in full accordance with the United Kingdom Home Office Animal (Scientific Procedures) Act 1986. Min mice and cyclin D1 knockout mice have been described previously (9
, 10)
. Female cyclin D1 knockout mice (Ccnd1-/-) are unable to suckle newborn pups due to the failure of mammary tissue development. Heterozygous females (Ccnd1+/-) were crossed with male Min mice (Apcmin/+). Of the F1 generation, male mice with the genotype (Ccnd1+/-; Apcmin/+) were crossed with either (Ccnd1+/-); Apcmin/+) or (Ccnd1+/-; Apc+/+) females. Only the F2 Min mice (i.e., APCmin/+) with all the Ccnd1 genotypes were included in the study (i.e., Ccnd1-/- / Ccnd1+/- / Ccnd1+/+). The F2 Min mice were sacrificed between 97 and 139 days, and the intestines were examined for the presence of tumors. Tail tissue was collected from all mice after sacrifice, and the mice were regenotyped for Apc and Ccnd1.
Genotyping of Tissue Samples.
DNA was extracted from tail snips or tumor tissue using a DNeasy Tissue kit (Qiagen) in accordance with the manufacturer’s instructions. All genotyping was done in duplicate using PCR assays. Mice were genotyped for cyclin D1 and the modifier gene, Mom-1, as described previously (9
, 11)
. Mice were genotyped for Apc using a modified version of a previously described protocol (12)
. In the current study, typing for Apc was carried out in a multiplexed PCR reaction over 35 cycles with an annealing temperature of 50°C and a Mg2+ concentration of 2.5 mM. Primers (described in Ref. 12
) were used at the following concentrations: MAPC9, 0.02 µM; and MAPCmt and MAPC15, 0.2 µM.
Preparation of Tissue Samples for Tumor Counting and Histological Analysis.
All mice underwent a thorough postmortem examination at the time of sacrifice. The intestinal tract from the stomach to the rectum was removed in toto and subdivided into four segments consisting of three equal lengths of small intestine and the whole of the large intestine. Each segment was flushed with PBS, cut longitudinally, opened flat, and fixed in 10% buffered formal saline. After overnight fixation, the tissue samples were placed in 70% ethanol and stained with 0.5% (v/v) toluidine blue dye. Staining with this dye enhanced the morphological differences between adenomas and lymphoid polyps to allow easy discrimination between the two types of polyp. Tumors were counted using a dissecting microscope at x6 magnification, and tumor diameter was measured. To eliminate interobserver error, all counts were done by a single observer blinded to the genotype of the mice. Approximately 30% of the cases were also counted by a second observer to confirm the results of the first observer. After tumor counting, intestines from approximately 30% of the study population underwent paraffin processing, and H&E-stained sections were prepared and studied.
As part of the study, individual tumors underwent further molecular analysis. In these cases, after the intestinal segments were opened, tumors were excised, and each tumor was bisected. One half was snap frozen in liquid nitrogen. The other half was fixed in formalin and then examined histologically to confirm the presence of tumor tissue.
RT-PCR Analysis of Tumors.
RNA was extracted from tumor tissue using the FastRNA Kit-Green (Q-Biogene) in accordance with the manufacturer’s instructions. Complementary DNA was produced from the RNA using the First Strand cDNA synthesis kit (MBI Fermentas) in accordance with the manufacturer’s instructions. PCR primers were designed for mouse cyclin D1 (Ccnd1; accession number NM_007631), cyclin D2 (Ccnd2; accession number NM_009829), cyclin D3 (Ccnd3; Genbank accession number NM_007632), and glyceraldehyde-3-phosphate dehydrogenase (MUSGAPDH; accession number M32599) using the Primer 3 program.4
The specificity of the primers was confirmed by sequencing the products. Primer sequences and cycling conditions are available from the authors.
Statistical Analysis.
All statistical analyses were carried out using Stata 7 (Stata Corp., College Station, TX). Tumor numbers among the three Ccnd1 genotypes were compared in two ways. First, the Mann-Whitney test for nonparametric data was used. Second, the data were log-transformed for normalization and then compared by ANOVA.
|
Results and Discussion
|
|---|
Cyclin D1 Is Not Essential for Intestinal Tumorigenesis.
Cyclin D1 is a known oncogene that is mutated in a large variety of epithelial and mesenchymal cancers. It has been shown to be a gene specifically targeted for induction by ß-catenin in both human and murine intestinal epithelial cells. Because most cyclin D1 mutations result in increased amounts of wild-type protein (rather than altered protein structure or function), it would appear, from first principles, that it represents an important target in ß-catenin-mediated tumorigenesis. We examined the role of cyclin D1 during intestinal tumorigenesis through the generation of Min mice that also carried knockout mutations of cyclin D1. A total of 75 Min mice (Apcmin/+) were generated with the three different cyclin D1 genotypes [wild-type (Ccnd1+/+/Apcmin/+; n = 17), heterozygous (Ccnd1+/-/Apcmin/+; n = 36), and null (Ccnd1-/-/Apcmin/+; n = 22; Table 1
). The genotypes in the study population were confirmed both pre- and postmortem. The intestines of the mice were examined, and tumors were found in all Min mice irrespective of the Ccnd1 genotype. Histological examination confirmed that the tumors were indeed intestinal adenomas (Fig. 1)
, and no histological differences were apparent between the tumors with differing Ccnd1 genotypes.
View larger version (120K):
[in this window]
[in a new window]
|
Fig. 1. Development of adenomatous tumors in Min mice that are null for cyclin D1 (Ccnd1-/-/Apcmin/+). The left panel is a low-power picture of a "Swiss roll" specimen of gut showing at least two tumors. The right panel is a high-power picture of one of the tumors.
|
|
Neoplastic change is frequently accompanied by complex changes in the chromatin. To exclude the possibility that revertant mutations had occurred that had restored wild-type cyclin D1, individual tumors were examined. Eight tumors were harvested (three from Ccnd1-/- mice, four from Ccnd1+/- mice, and one from a Ccnd1+/+ mouse). These were confirmed by histology to be adenomatous and were then regenotyped. All tumors showed the same Ccnd1 genotype as had been seen in the tail snips (data not shown), thereby excluding revertant mutations.
One of the accepted complications of gene knockouts is the production of hypomorphic alleles. In this situation, aberrant message splicing results in the production of low amounts of wild-type mRNA that can profoundly affect the phenotype. To exclude hypomorphic alleles, seven tumors were harvested (three Ccnd1-/-, two Ccnd1+/-, and two Ccnd1+/+ tumors), and adenomatous features were confirmed by histology. These tumors were examined by RT-PCR for expression of MUSGAPDH (a housekeeping gene to confirm template integrity) and cyclins D1/D2/D3. All tumors showed expression of cyclins D2 and D3. Expression of cyclin D1 was seen in Ccnd1+/- and Ccnd1+/+ tumors but was not seen in tumors with the Ccnd1-/-genotype (Fig. 2)
. This confirms that tumor development did not occur as a result of hypomorphic alleles.
View larger version (131K):
[in this window]
[in a new window]
|
Fig. 2. The top panel shows the unequivocal histological features of neoplasia in four tumors. The bottom panel shows the expression of cyclin D1 and cyclin D2 (by RT-PCR) in these four tumors. Tumors P4f2801 and P5f2801 are from the same mouse, which is Ccnd1-/-/Apcmin/+, and show that there is expression of cyclin D2 but no expression of cyclin D1, indicating tumor development in the absence of cyclin D1. Tumor P2h2801 is from a mouse that is Ccnd1+/-/Apcmin/+, whereas tumor P7h230801 is from a mouse that is Ccnd1+/+/Apcmin/+. In these tumors, there is expression of both cyclin D1 and cyclin D2 (CD1, cyclin D1; CD2, cyclin D2).
|
|
These data thus show that, although cyclin D1 is unequivocally and specifically up-regulated by ß-catenin signaling, it is not essential for intestinal tumorigenesis in Min mice. Thus cyclin D1 activity may not be necessary, or, if it is necessary, alternative pathways can be recruited. This is in stark contrast to mammary tumorigenesis, where Ccnd1-/- mice are resistant to H-ras- and c-neu-induced breast cancers (13)
. Therefore, although cyclin D1 has been proposed as a target for antitumor therapy, the implication from our data is that, in intestinal tumors at least, such therapy may have limitations (13
, 14)
. The nature of putative alternative pathways is uncertain; cyclins D2, D3, and E are possibilities, although previous reports have not shown increased expression in CRC (7
, 8
, 15)
. Another possibility is an increase in functional activity of cell cycle-related proteins without increasing the absolute levels. In this respect, it is noteworthy that c-myc, another target of ß-catenin, has been shown to increase cyclin E-cyclin-dependent kinase 2 activity (16
, 17)
.
It could be argued that the results are not surprising because the fact that Ccnd1-/- mice are viable indicates innate redundancy. However, tumor development depends on key mutations occurring in the appropriate context. Mice deficient in p53 protein can develop normally due to redundancy within the system. In the presence of key mutations, that redundancy cannot compensate, and tumors develop (18)
. In this model, because cyclin D1 is a target gene for ß-catenin, the precise context of tumor initiation has been recreated, and cyclin D1 has been appropriately tested.
Cyclin D1 May Act as a Modifier Gene.
As part of the postmortem examination, the total number of small and large intestinal tumors was counted. There was a large range of tumor numbers in each of the Ccnd1 genotypes, probably indicating the presence of powerful modifier genes that are unlinked to Ccnd1 (Fig. 3A
; Table 1
). In the study population overall, the small intestinal tumor numbers ranged from 1 to 129. Further analysis showed that the modifier effect was not due to known modifying loci because no animals carried the Mom1R allele (Fig. 3B)
.
View larger version (57K):
[in this window]
[in a new window]
|
Fig. 3. A, distribution of tumors in Min mice with each of the three cyclin D1 genotypes studied. WT, wild-type (Ccnd1+/+); Het, heterozygous (Ccnd1+/-); Null, homozygous knockout (Ccnd1-/-). B, analysis for the modifier gene Mom1. A PCR reaction generates a product of 500 bp. The Mom1R allele carries a BamHI restriction site that cleaves the product into 400- and 100-bp fragments. A mutation present in the Mom1S allele results in loss of the restriction site. * represents a positive control homozygous for the Mom1R allele. Lanes 1–8 are samples from the study population.
|
|
To analyze the effect of cyclin D1, the Ccnd1+/- and Ccnd1+/+ groups were combined, and tumor numbers were compared with the Ccnd1-/- group. This showed that, despite the wide range in tumor numbers and our data showing that cyclin D1 is not essential for tumorigenesis, the lack of cyclin D1 in tissues did have an apparent effect on tumor development. Significantly fewer tumors developed in the Ccnd1-/- mice when compared with the combined Ccnd1+/- and Ccnd1+/+ groups (P < 0.005, Mann-Whitney t test; P < 0.003, ANOVA test after log transformation). There was no difference in tumor size between the various cyclin D1 genotypes (data not shown).
The differences in tumor number are intriguing, although the data must be interpreted with caution. Cyclin D1 knockout mice are known to be smaller than heterozygous or wild-type mice, and this feature was also seen in our sample. However there was no association between tumor number and animal weight (data not shown). When the tumor counts were also corrected for length of the intestines, the differences between the genotypes were still significant (Ccnd1-/- mice, mean 0.54 tumors/cm gut; combined Ccnd1+/- and Ccnd1+/+ groups, mean 1.11 tumors/cm gut; P < 0.02, ANOVA). The most likely explanation for the reduction in tumor number in the Ccnd1-/- mice is that Ccnd1 has some modifier activity, although effects from variation at linked loci cannot be entirely excluded. However, the results do support recent data in humans showing an earlier onset of CRC in patients with a protein stabilizing polymorphism in the cyclin D1 gene (19
, 20)
. This implies that, in both mice and humans, cyclin D1 may have a role as a disease-modifying gene in intestinal tumorigenesis.
|
ACKNOWLEDGMENTS
|
|---|
We thank Tracy Crafton, Mike Bradburn, and George Elia for technical assistance with animal husbandry, assistance with statistical analysis, and preparation of histological sections, respectively.
|
FOOTNOTES
|
|---|
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 Supported by the Medical Research Council (United Kingdom) and Cancer Research UK. 
2 To whom requests for reprints should be addressed, at Oxford Molecular Pathology Group, Level 3, The Women’s Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom. Phone: 44-1865-221021; Fax: 44-1865-769141; E-mail: mohammad.ilyas{at}obs-gyn.ox.ac.uk
3 The abbreviations used are: CRC, colorectal cancer; Min, multiple intestinal neoplasia; RT-PCR, reverse transcription-PCR; APC, adenomatous polyposis coli.
4 http://www-genome.wi.mit.edu/cgi-bin/primer/primer3.cgi.
Received 5/13/02.
Accepted 6/26/02.
|
REFERENCES
|
|---|
- Ilyas M., Straub J., Tomlinson I. P. M., Bodmer W. F. Genetic pathways in colorectal and other cancers. Eur. J. Cancer, 35: 335-351, 1999.
- Ilyas M., Tomlinson I. P. M., Rowan A., Pignatelli M., Bodmer W. F. ß-Catenin mutations in cell lines established from human colorectal cancers. Proc. Natl. Acad. Sci. USA, 94: 10330-10334, 1997.[Abstract/Free Full Text]
- Morin P. J., Sparks A. B., Korinek V., Barker N., Clevers H., Vogelstein B., Kinzler K. W. Activation of ß-catenin-Tcf signaling in colon cancer by mutations in ß-catenin or APC. Science (Wash. DC), 275: 1787-1790, 1997.[Abstract/Free Full Text]
- Sparks A. B., Morin P. J., Vogelstein B., Kinzler K. W. Mutational analysis of the APC/ß-catenin/Tcf pathway in colorectal cancer. Cancer Res., 58: 1130-1134, 1998.[Abstract/Free Full Text]
- Dickson C., Fantl V., Gillett C., Brookes S., Bartek J., Smith R., Fisher C., Barnes D., Peters G. Amplification of chromosome band 11q13 and a role for cyclin D1 in human breast-cancer. Cancer Lett., 90: 43-50, 1995.[Medline]
- Rosenberg C. L., Wong E., Petty E. M., Bale A. E., Tsujimoto Y., Harris N. L., Arnold A. Prad1, a candidate Bcl1 oncogene: mapping and expression in centrocytic lymphoma. Proc. Natl. Acad. Sci. USA, 88: 9638-9642, 1991.[Abstract/Free Full Text]
- Tetsu O., McCormick F. ß-Catenin regulates expression of cyclin D1 in colon carcinoma cells. Nature (Lond.), 398: 422-426, 1999.[Medline]
- Arber N., Hibshoosh H., Moss S. F., Sutter T., Zhang Y., Begg M., Wang S. B., Weinstein I. B., Holt P. R. Increased expression of cyclin D1 is an early event in multistage colorectal carcinogenesis. Gastroenterology, 110: 669-674, 1996.[Medline]
- Fantl V., Stamp G., Andrews A., Rosewell I., Dickson C. Mice lacking cyclin D1 are small and show defects in eye and mammary-gland development. Genes Dev., 9: 2364-2372, 1995.[Abstract/Free Full Text]
- Su L. K., Kinzler K. W., Vogelstein B., Preisinger A. C., Moser A. R., Luongo C., Gould K. A., Dove W. F. Multiple intestinal neoplasia caused by a mutation in the murine homolog of the Apc gene. Science (Wash. DC), 256: 668-670, 1992.[Abstract/Free Full Text]
- Gould K. A., Luongo C., Moser A. R., McNeley M. K., Borenstein N., Shedlovsky A., Dove W. F., Hong K., Dietrich W. F., Lander E. S. Genetic evaluation of candidate genes for the Mom1 modifier of intestinal neoplasia in mice. Genetics, 144: 1777-1785, 1996.[Abstract]
- Dietrich W. F., Lander E. S., Smith J. S., Moser A. R., Gould K. A., Luongo C., Borenstein N., Dove W. Genetic identification of Mom-1, a majormodifier locus affecting Min-induced intestinal neoplasia in the mouse. Cell, 75: 631-639, 1993.[Medline]
- Yu Q. Y., Geng Y., Sicinski P. Specific protection against breast cancers by cyclin D1 ablation. Nature (Lond.), 411: 1017-1021, 2001.[Medline]
- Arber N., Doki Y., Han E. K. H., Sgambato A., Zhou P., Kim N. H., Delohery T., Klein M. G., Holt P. R., Weinstein I. B. Antisense to cyclin D1 inhibits the growth and tumorigenicity of human colon cancer cells. Cancer Res., 57: 1569-1574, 1997.[Abstract/Free Full Text]
- Bartkova J., Zemanova M., Bartek J. Abundance and subcellular localisation of cyclin D3 in human tumours. Int. J. Cancer, 65: 323-327, 1996.[Medline]
- Dang C. V., Resar L. M. S., Emison E., Kim S., Li Q., Prescott J. E., Wonsey D., Zeller K. Function of the c-Myc oncogenic transcription factor. Exp. Cell Res., 253: 63-77, 1999.[Medline]
- He T. C., Sparks A. B., Rago C., Hermeking H., Zawel L., da Costa L. T., Morin P. J., Vogelstein B., Kinzler K. W. Identification of c-MYC as a target of the APC pathway. Science (Wash. DC), 281: 1509-1512, 1998.[Abstract/Free Full Text]
- Jacks T., Remington L., Williams B. O., Schmitt E. M., Halachmi S., Bronson R. T., Weinberg R. A. Tumor spectrum analysis in p53-mutant mice. Curr. Biol., 4: 1-7, 1994.[Medline]
- Kong S. M., Amos C. I., Luthra R., Lynch P. M., Levin B., Frazier M. L. Effects of cyclin D1 polymorphism on age of onset of hereditary nonpolyposis colorectal cancer. Cancer Res., 60: 249-252, 2000.[Abstract/Free Full Text]
- Kong S. M., Wei Q. Y., Amos C. I., Lynch P. M., Levin B., Zong J. H., Frazier M. L. Cyclin D1 polymorphism and increased risk of colorectal cancer at young age. J. Natl. Cancer Inst. (Bethesda), 93: 1106-1108, 2001.[Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
U. Dougherty, A. Sehdev, S. Cerda, R. Mustafi, N. Little, W. Yuan, S. Jagadeeswaran, A. Chumsangsri, J. Delgado, M. Tretiakova, et al.
Epidermal Growth Factor Receptor Controls Flat Dysplastic Aberrant Crypt Foci Development and Colon Cancer Progression in the Rat Azoxymethane Model
Clin. Cancer Res.,
April 15, 2008;
14(8):
2253 - 2262.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Schneikert and J. Behrens
The canonical Wnt signalling pathway and its APC partner in colon cancer development
Gut,
March 1, 2007;
56(3):
417 - 425.
[Full Text]
[PDF]
|
|
|
|
|
|
|
O. J. Sansom, K. R. Reed, M. van de Wetering, V. Muncan, D. J. Winton, H. Clevers, and A. R. Clarke
Cyclin D1 Is Not an Immediate Target of {beta}-Catenin following Apc Loss in the Intestine
J. Biol. Chem.,
August 5, 2005;
280(31):
28463 - 28467.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
O. M. Sieber, K. M. Howarth, C. Thirlwell, A. Rowan, N. Mandir, R. A. Goodlad, A. Gilkar, B. Spencer-Dene, G. Stamp, V. Johnson, et al.
Myh Deficiency Enhances Intestinal Tumorigenesis in Multiple Intestinal Neoplasia (ApcMin/+) Mice
Cancer Res.,
December 15, 2004;
64(24):
8876 - 8881.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M D Crabtree, C Fletcher, M Churchman, S V Hodgson, K Neale, R K S Phillips, and I P M Tomlinson
Analysis of candidate modifier loci for the severity of colonic familial adenomatous polyposis, with evidence for the importance of the N-acetyl transferases
Gut,
February 1, 2004;
53(2):
271 - 276.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. C. Faux, J. L. Ross, C. Meeker, T. Johns, H. Ji, R. J. Simpson, M. J. Layton, and A. W. Burgess
Restoration of full-length adenomatous polyposis coli (APC) protein in a colon cancer cell line enhances cell adhesion
J. Cell Sci.,
January 22, 2004;
117(3):
427 - 439.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. M. Rowlands, I. V. Pechenkina, S. J. Hatsell, R. G. Pestell, and P. Cowin
Dissecting the roles of {beta}-catenin and cyclin D1 during mammary development and neoplasia
PNAS,
September 30, 2003;
100(20):
11400 - 11405.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
T. Yamada, Y. Mori, R. Hayashi, M. Takada, Y. Ino, Y. Naishiro, T. Kondo, and S. Hirohashi
Suppression of Intestinal Polyposis in Mdr1-deficient ApcMin/+ Mice
Cancer Res.,
March 1, 2003;
63(5):
895 - 901.
[Abstract]
[Full Text]
[PDF]
|
|
|
Top
ABSTRACT
Introduction
