Evidence for a p27 tumor suppressive function independent of its role regulating cell proliferation in the prostate

Anti gC1qR/p32/HABP1 Antibody Therapy Decreases Tumor Growth in an Orthotopic Murine Xenotransplant Model of Triple Negative Breast Cancer

gC1qR is highly expressed in breast cancer and plays a role in cancer cell proliferation. This study explored therapy with gC1qR monoclonal antibody 60.11, directed against the C1q binding domain of gC1qR, in a murine orthotopic xenotransplant model of triple negative breast cancer. MDA231 breast cancer cells were injected into the mammary fat pad of athymic nu/nu female mice. Mice were segregated into three groups (n = 5, each) and treated with the vehicle (group 1) or gC1qR antibody 60.11 (100 mg/kg) twice weekly, starting at day 3 post-implantation (group 2) or when the tumor volume reached 100 mm³ (group 3). At study termination (d = 35), the average tumor volume in the control group measured 895 ± 143 mm³, compared to 401 ± 48 mm³ and 701 ± 100 mm³ in groups 2 and 3, respectively (p < 0.05). Immunohistochemical staining of excised tumors revealed increased apoptosis (caspase 3 and TUNEL staining) in 60.11-treated mice compared to controls, and decreased angiogenesis (CD31 staining). Slightly decreased white blood cell counts were noted in 60.11-treated mice. Otherwise, no overt toxicities were observed. These data are the first to demonstrate an in vivo anti-tumor effect of 60.11 therapy in a mouse model of triple negative breast cancer.

Deletion of Cdkn1b in ACI rats leads to increased proliferation and pregnancy-associated changes in the mammary gland due to perturbed systemic endocrine environment

Mammary epithelial progenitors are the normal cell-of-origin of breast cancer. We previously defined a population of p27⁺ quiescent hormone-responsive progenitor cells in the normal human breast whose frequency associates with breast cancer risk. Here, we describe that deletion of the Cdkn1b gene encoding the p27 cyclin-dependent kinase inhibitor in the estrogen-induced mammary tumor-susceptible ACI rat strain leads to a decrease in the relative frequencies of Cd49b⁺ mammary luminal epithelial progenitors and pregnancy-related differentiation. We show by comprehensive gene expression profiling of purified progenitor and differentiated mammary epithelial cell populations that p27 deletion has the most pronounced effects on luminal progenitors. Cdkn1b^-/- females have decreased fertility, but rats that are able to get pregnant had normal litter size and were able to nurse their pups implying that loss of p27 in ACI rats does not completely abrogate ovarian function and lactation. Reciprocal mammary gland transplantation experiments indicate that the p27-loss-induced changes in mammary epithelial cells are not only caused by alterations in their intrinsic properties, but are likely due to altered hormonal signaling triggered by the perturbed systemic endocrine environment observed in Cdkn1b^-/- females. We also observed a decrease in the frequency of mammary epithelial cells positive for progesterone receptor (Pr) and FoxA1, known direct transcriptional targets of the estrogen receptor (Erα), and an increase in phospho-Stat5 positive cells commonly induced by prolactin (Prl). Characterization of genome-wide Pr chromatin binding revealed distinct binding patterns in mammary epithelial cells of Cdkn1b^+/+ and Cdkn1b^-/- females and enrichment in genes with known roles in Notch, ErbB, leptin, and Erα signaling and regulation of G1-S transition. Our data support a role for p27 in regulating the pool size of hormone-responsive luminal progenitors that could impact breast cancer risk.

The frequency and proliferation of tissue-specific stem and progenitor cells is associated with the risk of malignancy. Thus, regulators of the pool size and proliferation of progenitor cells determine cancer risk. p27 is a key regulator of cellular proliferation and is required for the terminal differentiation of a number of cell types. Here we show that genetic deletion of Cdkn1b in ACI rats susceptible to estrogen-induced mammary tumors decreases the relative fraction of Cd49b⁺ luminal progenitors identifying p27 as a key regulator of the proliferation and pool size of these cells. Progesterone, acting via the progesterone receptor (Pr), is an important regulator of mammary epithelial cell proliferation and differentiation. Based on ChIP-seq we found that Pr targets different sets of genes in Cdkn1b^+/+ and Cdkn1b^-/- mammary epithelium and that this is associated with differences in proliferation and differentiation states. Thus, p27 regulates breast cancer risk and tumor development via regulating the pool size and hormonal-responsiveness of luminal progenitors.

Overexpression of ADAM9 Promotes Colon Cancer Cells Invasion

INTRODUCTION

ADAM9 is a membrane-anchored metalloprotease that is markedly upregulated in several human carcinomas. We previously showed that ADAM9 staining was increased in colon cancer tissues. In the present work, we investigated the expression pattern of ADAM9 in colon cell lines, and the effects of overexpression ADAM9 on colon cancer proliferation and invasion.

MATERIALS AND METHODS

ADAM9 mRNA expression was determined in colon cancer tissues by RT-PCR assay, meanwhile, ADAM9 DNA and protein levels were measured in colon cancer cell lines by PCR and western blot, respectively. ADAM9 transfection was carried out in HT-29 colon cancer cells, and cell growth was measured by MTT assay, cell invasion ability was assessed by Matrigel assay.

RESULTS

ADAM9 mRNA was upregulated in colon cancer tissues, ADAM9 DNA and protein was overexpressed in Lovo cell lines, while the ADAM9 expression levels in HT-29, HCT-8, and Ls174t cells were below the levels of detection. Enhanced ADAM9 expression by ADAM9 transfection in HT-29 cells promoted cell invasion without increasing cell proliferation.

CONCLUSIONS

These results suggest that ADAM9 contributes to cell invasion and progression in colon cancer.

Increased number of multi-oocyte follicles (MOFs) in juvenile p27Kip1 mutant mice: potential role of granulosa cells

STUDY QUESTION

Why are female mice that lack a functional p27 protein infertile?

SUMMARY ANSWER

The absence of a functional p27 leads to a dramatic increase in the number of multi-oocyte follicles (MOFs) in juvenile female mice; p27 would promote the individualization of follicles favoring the development of fertile eggs.

WHAT IS KNOWN ALREADY

p27-/- female mice are infertile. p27 suppresses excessive follicular endowment and activation and promotes follicular atresia in mice.

MATERIALS AND METHODS

Ovaries from wild type (WT) and p27Kip1 mutant mice aged 2, 4 and 12 weeks were subjected to immunohistochemistry/immunofluorescence. The slides with whole organs serially sectioned were scanned and examined by image analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared with WT, p27Kip1 mutant pre-pubertal mice had a greater number of oocytes, a greater number of growing follicles and a greater number of MOFs. These differences were statistically significant (P < 0.05), particularly in the case of MOFs (P > 0.001). The unusually large number of MOFs in juvenile p27-deficient mice is a novel observation. In WT mice p27 protein remains present in the oocyte nucleus but gradually decreases in the ooplasm during follicular growth, while granulosa cells show dynamic, follicle stage-related changes.

LIMITATIONS, REASONS FOR CAUTION

These results have been obtained in mice and they cannot be directly extrapolated to humans.

WIDER IMPLICATIONS OF THE FINDINGS

The dramatic increase in the numbers of MOFs in juvenile p27 mutants has not been previously reported. The number of MOFs declines sharply as the mice become sexually mature, pointing to their negative selection. These findings open a new approach to the study of sterility.

STUDY FUNDING/COMPETING INTERESTS

This study has been funded by the Basque Government, Dept. of Health grant 2007111063 and Dept. of Industry (Saiotek) grant S-PC11UN008. Jairo Perez-Sanz was the recipient of a grant from Fundación Jesús de Gangoiti Barrera. The authors have no conflicts of interest to declare.

p27kip1 protein levels reflect a nexus of oncogenic signaling during cell transformation

SV40 small t-antigen (ST) collaborates with SV40 large T-antigen (LT) and activated rasv12 to promote transformation in a variety of immortalized human cells. A number of oncogenes or the disruption of the general serine-threonine phosphatase protein phosphatase 2A (PP2A) can replace ST in this paradigm. However, the relationship between these oncogenes and PP2A activity is not clear. To address this, we queried the connectivity of these molecules in silico. We found that p27 was connected to each of those oncogenes that could substitute for ST. We further determined that p27 loss can substitute for the expression of ST during transformation of both rodent and human cells. Conversely, knock-in cells expressing the degradation-resistant S10A and T187A mutants of p27 were resistant to the transforming activities of ST. This suggests that p27 is an important target of the tumor-suppressive effects of PP2A and likely an important target of the multitude of cellular oncoproteins that emulate the transforming function of ST.

p27(Kip1) deficiency promotes prostate carcinogenesis but does not affect the efficacy of retinoids in suppressing the neoplastic process

BACKGROUND

p27 is a cell cycle suppressor gene, whose protein is a negative regulator of cyclin/cdk complexes. p27 is also a potential target of retinoids in cancer prevention studies. In benign prostate hyperplasia (BPH), and in most carcinomas, p27(Kip1) is down-regulated, suggesting its potential resistance to retinoids. To test this hypothesis, we examined the efficacy of 9-cis retinoic acid (9cRA) to suppress prostate cell proliferation (PECP) and carcinogenesis in p27(Kip1) deficient mice.

METHODS

p27(Kip1) deficient (-/-), heterozygous (+/-) and homozygous (+/+) mice were treated for 7 days with testosterone, 9cRA, or with both, and cell proliferation in dorsolateral prostate (DLP) was determined by BrdU labeling. Prostate carcinogenesis was induced by N-Methyl-N-Nitrosourea (MNU) and hormone stimulation.

RESULTS

PECP in DLP of two-month-old mice of all genotypes was similar but significantly increased in old p27-/- mice only. Testosterone treatment increased PECP in all three p27 genotypes with the highest values in p27-/- mice. p27(Kip1) deficiency did not affect the response of PEC to 9cRA and to 9cRA+testosterone. The decrease of p27(Kip1) in p27+/- and p27-/- mice progressively increased the incidence and frequency of PIN and tumors. 9cRA suppressed PIN in all three p27 genotypes and this was associated with decreased PECP and increased cellular senescence.

CONCLUSIONS

This data indicates that p27(Kip1) deficiency promotes prostate cell proliferation and carcinogenesis but does not affect 9cRA's potential to suppress prostate carcinogenesis, suggesting that patients with PIN and carcinomas lacking or having a low level of p27(Kip1) expression may also benefit from clinical trials with retinoids.

Defective DNA double-strand break repair underlies enhanced tumorigenesis and chromosomal instability in p27-deficient mice with growth factor-induced oligodendrogliomas

The tumor suppressive activities of the Kip-family of cdk inhibitors often go beyond their role in regulating the cell cycle. Here, we demonstrate that p27 enhances Rad51 accumulation during repair of double-strand DNA breaks. Progression of PDGF-induced oligodendrogliomas was accelerated in mice lacking the cyclin-cdk binding activities of p27^kip1. Cell lines were developed from RCAS-PDGF infection of nestin-tv-a brain progenitor cells in culture. p27 deficiency did not affect cell proliferation in early passage cell lines; however, the absence of p27 affected chromosomal stability. In p27 deficient cells, the activation of Atm and Chk2, and the accumulation of γH2AX was unaffected compared to wild type cells, and the number of phospho-histone H3 staining mitotic cells was decreased, consistent with a robust G2/M checkpoint activation. However, the percentage of Rad51 foci positive cells was decreased, and the kinase activity that targets the C-terminus of BRCA2, regulating BRCA2/Rad51 interactions, was increased in lysates derived from p27 deficient cells. Increased numbers of chromatid breaks in p27 deficient cells that adapted to the checkpoint were also observed. These findings suggest that Rad51-dependent repair of double stranded breaks was hindered in p27 deficient cells, leading to chromosomal instability, a hallmark of cancers with poor prognosis.

Inhibition of PI-3K restores nuclear p27Kip1 expression in a mouse model of Kras-driven lung cancer

Reduced expression of the CDK inhibitor p27(Kip1) (p27) in human lung cancer correlates with tumor aggressiveness and poor prognosis. However, the regulation of p27 expression and the role of p27 during lung cancer are poorly understood. Urethane-induced lung tumors in mice frequently harbor mutations in the Kras oncogene, and in this study, we use this model to address the regulation of p27 during tumorigenesis. The Ras effector Akt is known to regulate p27 mRNA abundance by phosphorylating and inactivating the FOXO transcription factors. Phosphorylated Akt and FOXO proteins were both increased in lung tumors, correlating with a reduction in p27 mRNA transcript. Akt also directly phosphorylates p27 and regulates its nuclear/cytoplasmic localization. Tumors showed a reduced nuclear/cytoplasmic ratio of p27 protein, together with an increase in phosphorylated Thr197 p27 in the cytoplasmic pool. Treatment of lung tumor-bearing mice with the phosphoinositol-3 kinase inhibitor LY294002 induced a rapid decrease in phosphorylated Akt and phosphorylated p27, concomitant with an increase in nuclear p27. Germline p27 deficiency accelerated both the growth and malignant progression of urethane-induced lung tumors, and did so in a cell autonomous manner, confirming a causal role of p27 in tumor suppression. These results show that p27 is a potent barrier to the growth and malignant progression of Kras-initiated lung tumors. Further, the reduction of nuclear p27 in tumors is mediated by oncogene signaling pathways, which can be reversed by pharmacological agents.

National Academy of Clinical Biochemistry Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers

Background: Updated National Academy of Clinical Biochemistry (NACB) Laboratory Medicine Practice Guidelines for the use of tumor markers in the clinic have been developed.

Methods: Published reports relevant to use of tumor markers for 5 cancer sites—testicular, prostate, colorectal, breast, and ovarian—were critically reviewed.

Results: For testicular cancer, α-fetoprotein, human chorionic gonadotropin, and lactate dehydrogenase are recommended for diagnosis/case finding, staging, prognosis determination, recurrence detection, and therapy monitoring. α-Fetoprotein is also recommended for differential diagnosis of nonseminomatous and seminomatous germ cell tumors. Prostate-specific antigen (PSA) is not recommended for prostate cancer screening, but may be used for detecting disease recurrence and monitoring therapy. Free PSA measurement data are useful for distinguishing malignant from benign prostatic disease when total PSA is &lt;10 μg/L. In colorectal cancer, carcinoembryonic antigen is recommended (with some caveats) for prognosis determination, postoperative surveillance, and therapy monitoring in advanced disease. Fecal occult blood testing may be used for screening asymptomatic adults 50 years or older. For breast cancer, estrogen and progesterone receptors are mandatory for predicting response to hormone therapy, human epidermal growth factor receptor-2 measurement is mandatory for predicting response to trastuzumab, and urokinase plasminogen activator/plasminogen activator inhibitor 1 may be used for determining prognosis in lymph node–negative patients. CA15-3/BR27–29 or carcinoembryonic antigen may be used for therapy monitoring in advanced disease. CA125 is recommended (with transvaginal ultrasound) for early detection of ovarian cancer in women at high risk for this disease. CA125 is also recommended for differential diagnosis of suspicious pelvic masses in postmenopausal women, as well as for detection of recurrence, monitoring of therapy, and determination of prognosis in women with ovarian cancer.

Conclusions: Implementation of these recommendations should encourage optimal use of tumor markers.

Phase II trial of docetaxel with rapid androgen cycling for progressive noncastrate prostate cancer

PURPOSE

We evaluated rapid androgen cycling in combination with docetaxel for men with progressive noncastrate prostate cancers.

PATIENTS AND METHODS

Noncastrate patients with 150 ng/dL) and an undetectable prostate-specific antigen (PSA;

RESULTS

A higher proportion of patients achieved the undetectable PSA outcome at 18 months in cohort 2 relative to cohort 1 (13% v 0%). The 16% incidence of febrile neutropenia was higher than that observed in patients was castration-resistant disease, which may have been related to a 50% reduction in overall docetaxel clearance in the noncastrate group. There was no alteration in CYP3A4 activity (P = .87) or docetaxel clearance (P = .88) between cycles.

CONCLUSION

The undetectable PSA end point allows for a rapid screening of interventions for further study. Increasing the number of docetaxel cycles after a shorter period of testosterone repletion, and a longer duration of testosterone depletion, increased the proportion of men who achieved an undetectable PSA. The higher-than-expected incidence of febrile neutropenia may have been related to the reduced overall docetaxel clearance in patients with noncastrate versus castrate testosterone levels.

Collapse

Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Antineoplastic Combined Chemotherapy Protocols/administration & dosage
• Cytochrome P-450 CYP3A
• Cytochrome P-450 Enzyme System/metabolism
• Docetaxel
• Humans
• Leuprolide/administration & dosage
• Male
• Middle Aged
• Prostate-Specific Antigen/blood
• Prostatic Neoplasms/drug therapy
• Prostatic Neoplasms/metabolism
• Taxoids/administration & dosage
• Taxoids/pharmacokinetics
• Testosterone/administration & dosage
• Testosterone/metabolism

Collapse

Grants

• P30 CA006973-48 NCI NIH HHS
• P30 CA006973 NCI NIH HHS
• P50-CA92629 NCI NIH HHS
• P50 CA092629 NCI NIH HHS
• PC051382 NCI NIH HHS

Collapse

Affiliation(s)

Dana Rathkopf Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Michael A. Carducci Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Michael J. Morris Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Susan F. Slovin Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Mario A. Eisenberger Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Roberto Pili Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Samuel R. Denmeade Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Moshe Kelsen Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Tracy Curley Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA
Regina Priet Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Connie Collins Prostate Cancer Program, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD, USA
Martin Fleisher Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
Glenn Heller Department of Clinical Chemistry, Memorial Sloan-Kettering Cancer Center, New York, New York, USA
Sharyn D. Baker Pharmaceutical Sciences Department, St. Jude Children’s Research Hospital, Memphis, TN, USA
Howard I. Scher Genitourinary Oncology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA and Department of Medicine, Joan and Sanford Weill College of Medicine, New York, New York, USA

Collapse

Enhanced expression of Rab27A gene by breast cancer cells promoting invasiveness and the metastasis potential by secretion of insulin-like growth factor-II

In addition to the functions of transporting melanosome in melanocytes and releasing contents of lytic granules in CTLs, Rab27A was recently shown to be involved in exocytosis of insulin and chromaffin granules in endocrine cells; it was also reported to be expressed in an exceptionally broad range of specialized secretory cells. As autocrine and paracrine cytokines are essential for invasion and metastasis in some solid tumors, blocking them may be an effective strategy to prevent tumor dissemination. In the present study, we show that Rab27A is associated with invasive and metastatic potentials of human breast cancer cells. The overexpression of Rab27A protein redistributed the cell cycle and increased the invasive and metastatic abilities in breast cancer cells both in vitro and in vivo. We also certified that Rab27A conferred the invasive and metastatic phenotypes on breast cancer cells by promoting the secretion of insulin-like growth factor-II (IGF-II), which regulates the expression of p16, vascular endothelial growth factor, matrix metalloproteinase-9, cathepsin D, cyclin D1, and urokinase-type plasminogen activator. These data provide functional evidence that Rab27A acts as a novel mediator of invasion and metastasis promotion in human breast cancer cells, at least in part, through regulating the secretion of IGF-II, suggesting that synergistic suppression of Rab27A and IGF-II activities holds a promise for preventing breast cancer invasion and metastasis.

DNA damage signaling in hematopoietic cells: a role for Mre11 complex repair of topoisomerase lesions

The Mre11 complex promotes DNA double-strand break repair and regulates DNA damage signaling via activation of the ataxia-telangiectasia mutated (ATM) kinase. The hypermorphic Rad50(S) allele encodes a variant of Rad50, a member of the Mre11 complex. Cells expressing Rad50(S) experience constitutive ATM activation, which leads to precipitous apoptotic attrition in hematopoietic cells. In this study, we show that ATM activation by the Rad50S-containing Mre11 complex enhances the proliferation of LSK cells, a population consisting of hematopoietic stem cells and multipotent progenitor cells. In Rad50(S/S) mice, enhanced LSK proliferation triggers apoptotic attrition. This phenotype is mitigated when Rad50(S/S) is combined with mutations that alter either LSK cell quiescence (myeloid elf-1-like factor/ELF4-deficient mice) or hematopoietic differentiation (p21- and p27-deficient mice), indicating that the LSK population is a primary target of Rad50(S) pathology. We show that cells from Rad50(S/S) mice are hypersensitive to camptothecin, a topoisomerase I inhibitor that causes DNA damage primarily during DNA replication. On this basis, we propose that apoptotic attrition of Rad50(S/S) hematopoietic cells results from enhanced proliferation in the context of topoisomerase-associated DNA damage. Impairment of apoptosis in Rad50(S/S) mice promotes hematopoietic malignancy, suggesting that primitive hematopoietic cells serve as a reservoir of potentially oncogenic lesions in Rad50(S/S) mice. These data provide compelling evidence that the Mre11 complex plays a role in the metabolism of topoisomerase lesions in mammals, and further suggest that such lesions can accumulate in primitive hematopoietic cells and confer significant oncogenic potential.

SV40 reporter viruses

Three simian virus 40 (SV40) reporter viruses were constructed in this study. One expresses the green fluorescent protein (GFP) as a fusion protein with the first exon of large-T (LT) antigen and is useful for live-cell imaging. A second reporter virus has a FLAG epitope tag at the C-terminus of large-T antigen (vC-LT(FLAG)), and a third has the FLAG tag at the N-terminus of LT (vN-LT(FLAG)). The vC-LT(FLAG) construct grows to titers near those of wild-type (WT) virus and functions well as a reporter virus for SV40 infection. The vN-LT(FLAG) construct, while viable, has a defect in the production and spread of infectious particles. All three viruses are useful in detecting superinfecting virus in cells in which nuclear LT is already present, such as persistently infected human mesothelial cells.

Susceptibility of p27 kip1 knockout mice to urinary bladder carcinogenesis induced by N-butyl-N-(4-hydroxybutyl)nitrosamine may not simply be due to enhanced proliferation

Deregulated proliferation is one of the fundamental characteristics of carcinogenesis. p27 is one of the most well characterized negative cell cycle regulator. In our previous study, expression of p27 protein was found to be dramatically suppressed on stimulation of cell proliferation by calculi in the rodent urinary bladder, withdrawal of the insult resulting in re-expression of p27 and regression of urothelial hyperplastic lesions. In the present study, to evaluate how loss of function impacts on urinary bladder carcinogenesis, N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), a bladder carcinogen was given to p27 knockout mice. Males and females with either null, hetero or wild-type p27 alleles were divided into 2 groups, one given drinking water containing 0.05% BBN for 10 weeks and the other receiving distilled water, then, killed at week 20. The experiment was repeated for confirmation of the outcome. In the second experiment, performed with a larger number of animals, the incidence of urinary bladder carcinomas was significantly higher in female p27-null mice than in their wild-type counterparts. p27 deficiency also resulted in their increase of relative weights of urinary bladders and section areas of carcinomas in BBN-treated mice. Interestingly, while BrdU labeling indices generally increased with progression of mucosal proliferative lesions, from normal epithelium, through hyperplasia to carcinoma, there was no significant variation with the p27 genotype, in tumors as well as normal urothelium. These findings suggest that p27 deficient mice have elevated susceptibility to BBN-induction of urinary bladder carcinogenesis through a mechanism which might be independent of acceleration of cell cycling.

Inactivation of p27Kip1 promotes chemical mouse liver tumorigenesis in the resistant strain C57BL/6J

The biochemical function of p27Kip1 as an inhibitor of cyclin-dependent kinases is well-established, but the role of p27 as a tumor suppressor depends on specific cellular contexts. Previous studies using p27 knockout mice on mixed C57BL/6J x 129/Sv strain background did not find a tumor suppressor role of p27 in the liver. An important feature of mouse liver tumorigenesis is strain-dependent tumor susceptibility. Here, we determined the role of p27 in liver tumorigenesis in C57BL/6J mice, a liver tumor resistant strain, in response to a diethylnitrosamine (DEN) and phenolbarbital (PB) two-stage carcinogenesis protocol. At 6 mo of age, while livers of DEN-PB treated p27+/+ and p27-/- C57BL/6J mice appeared morphologically normal, p27-/- livers, but not p27+/+ livers, contained readily detectable glucose-6-phosphatase (G6Pase)-deficient foci. At the 9-mo time point, p27-/- mice developed significantly enhanced liver tumor phenotypes than p27+/+ mice as demonstrated by increased numbers and sizes of liver surface nodules, increased liver-to-body weight ratios, and increased numbers of G6Pase-deficient nodules and histologically diagnosed foci and adenomas in liver sections. Hepatic lesions in p27-/- livers contained more proliferating hepatocytes than lesions in p27+/+ livers, while the numbers of apoptotic cells appeared similar in lesions of both genotypes. Unexpectedly, tumors in p27-/- livers contained only slightly elevated Cdk2 kinase activity compared with normal livers. These results reveal a liver tumor suppressor role of p27 in this resistant mouse strain, and the need to further study the role of Cdk2 kinase in liver tumor promotion by p27 inactivation.

Somatic cell type specific gene transfer reveals a tumor-promoting function for p21(Waf1/Cip1)

How proteins participate in tumorigenesis can be obscured by their multifunctional nature. For example, depending on the cellular context, the cdk inhibitors can affect cell proliferation, cell motility, apoptosis, receptor tyrosine kinase signaling, and transcription. Thus, to determine how a protein contributes to tumorigenesis, we need to evaluate which functions are required in the developing tumor. Here we demonstrate that the RCAS/TvA system, originally developed to introduce oncogenes into somatic cells of mice, can be adapted to allow us to define the contribution that different functional domains make to tumor development. Studying the development of growth-factor-induced oligodendroglioma, we identified a critical role for the Cy elements in p21, and we showed that cyclin D1T286A, which accumulates in the nucleus of p21-deficient cells and binds to cdk4, could bypass the requirement for p21 during tumor development. These genetic results suggest that p21 acts through the cyclin D1–cdk4 complex to support tumor growth, and establish the utility of using a somatic cell modeling system for defining the contribution proteins make to tumor development.

A two-stage binomial test approach of gene identification in oligonucleotide arrays

Most statistical approaches summarize the probe-level expression data into gene-level measures, which then are used for downstream statistical analyses. However, there are some limitations in using the gene level data for analysis, such as nonhomogeneous probe effects and the interaction effect (e.g., alternative splicing). In this paper, we consider a two-stage binomial test with a weighted probe rank approach to determine differentially expressed genes. Using a series of benchmark gene array datasets, we show the two-stage binomial test approach yielded a higher positive predictivity and a higher sensitivity than the conventional RMA, GCRMA, Dchip, and ANOVA approaches. In data application, the two-stage binomial test identified a subset of genes strongly related to cell proliferation in the prolactin study, and a subset of genes associated with lymph node metastasis in the breast cancer dataset. In addition, by exploring the proportion of probes with expression changes and the probe expression plot, the two-stage binomial test helped detect an alternative splicing form of the prolactin gene in the prolactin study. In the breast cancer dataset, the approach also identified one potential alternative splicing gene.

Cooperation between p27 and p107 during endochondral ossification suggests a genetic pathway controlled by p27 and p130

Pocket proteins and cyclin-dependent kinase (CDK) inhibitors negatively regulate cell proliferation and can promote differentiation. However, which members of these gene families, which cell type they interact in, and what they do to promote differentiation in that cell type during mouse development are largely unknown. To identify the cell types in which p107 and p27 interact, we generated compound mutant mice. These mice were null for p107 and had a deletion in p27 that prevented its binding to cyclin-CDK complexes. Although a fraction of these animals survived into adulthood and looked similar to single p27 mutant mice, a larger number of animals died at birth or within a few weeks thereafter. These animals displayed defects in chondrocyte maturation and endochondral bone formation. Proliferation of chondrocytes was increased, and ectopic ossification was observed. Uncommitted mouse embryo fibroblasts could be induced into the chondrocytic lineage ex vivo, but these cells failed to mature normally. These results demonstrate that p27 carries out overlapping functions with p107 in controlling cell cycle exit during chondrocyte maturation. The phenotypic similarities between p107(-/-) p27(D51/D51) and p107(-/-) p130(-/-) mice and the cells derived from them suggest that p27 and p130 act in an analogous pathway during chondrocyte maturation.

Rapid androgen cycling as treatment for patients with prostate cancer

PURPOSE

To investigate the safety and feasibility of rapid androgen cycling for men with progressive prostate cancer.

EXPERIMENTAL DESIGN

Schedule 1 included a 4-week induction of androgen depletion, followed by 4-week treatment cycles of a monthly gonadotropin-releasing hormone agonist, testosterone on days 1 to 7, and an estrogen patch on days 8 to 21. Schedule 2 included a 12-week induction of androgen depletion followed by 4-week cycles of gonadotropin-releasing hormone agonist and testosterone, but no estrogens for patients with a prostate-specific antigen (PSA) nadir <1 ng/mL after induction. The primary end point was serially declining PSA trough values over six treatment cycles.

RESULTS

Thirty-six patients were treated; 27 were evaluable after cycling, of whom 8 of 12 (67%) and 9 of 15 (60%) on schedules 1 and 2, respectively, reached the end point. Five patients with PSA >1 ng/mL following induction did not cycle. No patient progressed radiographically or clinically during cycling. Three posttherapy PSA patterns were observed: a decline followed by a rapid increase in trough levels, a sustained decline with a plateau at a detectable nadir, and a decline to an undetectable nadir. Mean testosterone levels were castrate at the time of trough and in the normal physiologic range following androgen repletion. Major toxicities included grades 1 and 2 fatigue, hepatitis, gynecomastia, and hot flashes.

CONCLUSIONS

Rapid hormonal cycling is feasible and well tolerated, and successive declines in PSA troughs are achievable. Although the sample size was small, the proportion of patients achieving declining PSA at the end of six cycles was comparable with that reached with continuous androgen depletion therapy.

Cancer statistics, 2007

Each year, the American Cancer Society (ACS) estimates the number of new cancer cases and deaths expected in the United States in the current year and compiles the most recent data on cancer incidence, mortality, and survival based on incidence data from the National Cancer Institute, Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries and mortality data from the National Center for Health Statistics. This report considers incidence data through 2003 and mortality data through 2004. Incidence and death rates are age-standardized to the 2000 US standard million population. A total of 1,444,920 new cancer cases and 559,650 deaths for cancers are projected to occur in the United States in 2007. Notable trends in cancer incidence and mortality rates include stabilization of the age-standardized, delay-adjusted incidence rates for all cancers combined in men from 1995 through 2003; a continuing increase in the incidence rate by 0.3% per year in women; and a 13.6% total decrease in age-standardized cancer death rates among men and women combined between 1991 and 2004. This report also examines cancer incidence, mortality, and survival by site, sex, race/ethnicity, geographic area, and calendar year, as well as the proportionate contribution of selected sites to the overall trends. While the absolute number of cancer deaths decreased for the second consecutive year in the United States (by more than 3,000 from 2003 to 2004) and much progress has been made in reducing mortality rates and improving survival, cancer still accounts for more deaths than heart disease in persons under age 85 years. Further progress can be accelerated by supporting new discoveries and by applying existing cancer control knowledge across all segments of the population.

Differential gene expression of p27Kip1 and Rb knockout pituitary tumors associated with altered growth and angiogenesis

Mice lacking the p27Kip1 Cdk inhibitor, like mice lacking Rb, develop pituitary tumors involving pars intermedia melanotrophs, yet p27(Kip1) tumors are genetically distinct from Rb derived tumors as they exhibit haploid insufficiency. We compared tumors from mice with p27( Kip1) constitutive and tissue specific null mutations to tumors arising in tissue specific Rb knockout mice with the aim of determining whether they are distinguished by quantitative or qualitative differences. The rate of p27Kip1 knockout tumor development was strongly influenced by strain background due to polygenic strain modifiers in the C57BL/6J versus 129S4 strains but, unlike a prior report of Rb mutants, this impacted tumor incidence but not the tumor spectrum. p27Kip1 tumors were oligoclonal or polyclonal based on studies of X-chromosomal inactivation of Dock11. In contrast, Rb null tissue developed monoclonal neoplasms even in the absence of a requirement for Rb mutant clonal selection. Rb null tumors exhibited a higher proliferation rate and developed ischemic necrosis associated with an aberrant vasculature. p27Kip1 null tumors maintained normal vascular density, through a tumor cell dependent mechanism, but were more often hemorrhagic. Gene expression profiles distinguished p27Kip1 from Rb null tumors including significant differences in expression of Rb and E2F signature genes. Rb null tumors expressed higher levels of VEGF which, in other systems, is associated with dilated vessels, ineffective perfusion and tissue hypoxia. Mouse models lacking p27Kip1 and Rb may help us better understand the pathophysiology of MEN syndromes, retinoblastoma and other cancers that disrupt these important cell cycle inhibitors.

A pathway regulated by cell cycle inhibitor p27Kip1 and checkpoint inhibitor Smad3 is involved in the induction of T cell tolerance

Peripheral tolerance is essential for immunological homeostasis. Tolerant T cells are thought to arise after T cell receptor ligation in conditions that are nonpermissive for replication. Here we have investigated the function of the cell cycle inhibitor p27(Kip1) in tolerance induction in vivo using naive T cell receptor-transgenic cells lacking the cyclin-dependent kinase (Cdk)-binding domain of p27(Kip1)(p27delta). Wild-type but not p27delta cells underwent tolerization. Tolerized wild-type cells had impaired Cdk2 and Cdc2 kinase activity and failed to phosphorylate the checkpoint inhibitor Smad3, leading to enhanced expression of the Cdk inhibitor p15. In contrast, p27delta cells proliferated in tolerizing conditions because of Cdk kinase activation and phosphorylation of Smad3, which resulted in no upregulation of p15. Smad3 'knockdown' prevented tolerance induction, whereas expression of a Smad3 mutant resistant to Cdk-mediated phosphorylation recapitulated molecular and functional events of tolerance. Thus, p27(Kip1) is required during induction of tolerance and Smad3 regulates T cell responses 'downstream' of p27(Kip1).

Promoter SNPs in G1/S checkpoint regulators and their impact on the susceptibility to childhood leukemia

Mutations leading to the alteration of cell-cycle checkpoint functions are a common feature of most cancers. Because of the highly regulated nature of the cell cycle, it seems likely that variation in gene dosage of key components due to functional regulatory polymorphisms could play an important role in cancer development. Here we provide evidence of the involvement of promoter single-nucleotide polymorphisms (pSNPs) in the cyclin-dependent–kinase inhibitor genes CDKN2A, CDKN2B, CDKN1A, and CDKN1B in the etiology of childhood pre-B acute lymphoblastic leukemia (ALL). A case-control study, conducted in 240 patients with pre-B ALL and 277 healthy controls, combined with a family-based analysis using 135 parental trios, all of French-Canadian origin, were used to evaluate single-site genotypic as well as multilocus haplotypic associations for a total of 10 pSNPs. Using both study designs, we showed evidence of association between variants CDKN2A −222A, CDKN2B −593A, and CDKN1B −1608A, and an increased risk of ALL. These findings suggest that variable expression levels of cell-cycle inhibitor genes CDKN2A, CDKN2B, and CDKN1B due to regulatory polymorphisms could indeed influence the risk of childhood pre-B ALL and contribute to carcinogenesis.

Molecular markers in the diagnosis of prostate cancer

The genetic alterations leading to prostate cancer are gradually being discovered. A wide variety of genes have been associated with prostate cancer development as well as tumor progression. Knowledge of gene polymorphisms associated with disease aid in the understanding of important pathways involved in this process and may result in the near future in clinical applications. Urinary molecular markers will soon be available to aid in the decision of repeat prostate biopsies. Recent findings suggest the importance of androgen signaling in disease development and progression. The further understanding of interaction of inflammation, diet, and genetic predisposition will improve risk stratification in the near future.

ADAM12 is highly expressed in carcinoma-associated stroma and is required for mouse prostate tumor progression

The interaction between stromal cells and tumor cells is emerging as a critical aspect of tumor progression. Yet there is a paucity of molecular markers for cells participating in such interactions, and only few genes are known to play a critical role in this process. Here, we describe the identification of ADAM12 (a disintegrin and metalloprotease 12) as a novel marker for a subpopulation of stromal cells that are adjacent to epithelial tumor cells in three mouse carcinoma models (models for prostate, breast and colon cancer). Moreover, we show that ADAM12 is essential for tumor development and progression in the W10 mouse model for prostate cancer. These results suggest that ADAM12 might be a useful marker for stromal cells in mouse tumors that are likely to participate in stromal/tumor cell crosstalk, and that ADAM12 is a potential target for design of drugs that prevent carcinoma growth.

Regulation of cell proliferation in a stratified culture system of epithelial cells from prostate tissue

Mechanisms controlling epithelial proliferation and differentiation in the prostate have been primarily investigated in mouse models. The regulation of proliferation and differentiation is poorly understood in human prostate epithelial cells. In vivo, the glandular prostate epithelium consists of a p63-positive proliferating basal cell layer and a post-mitotic p27-positive secretory cell layer. We have established an organized stratified culture system of human primary prostate epithelial cells to gain insight into mechanisms regulating proliferation and differentiation. In this system, expression of p63 is observed in the bottom layer. In addition, BrdU incorporation persists even though cells are confluent. In contrast, in the upper layer, p63 expression is greatly diminished, p27 is expressed, and the cells are growth arrested. Overexpression of cyclin D1 or knockdown of p27 does not increase proliferation. After inactivation of the nuclear phosphoprotein Rb, the cell layers remain organized and cell proliferation increases only in the bottom layer. Furthermore, the expression of p63 remains confined to the bottom layer after Rb inactivation. Altogether, this in vitro model recapitulates certain aspects of in vivo growth regulation and differentiation and suggests that the loss of Rb family proteins in human cells trigger hyperplasia but is not sufficient for transformation.

Gene therapy for BCR-ABL+ human CML with dual phosphorylation resistant p27Kip1 and stable RNA interference using an EBV vector

BACKGROUND

BCR-ABL-mediated chronic myelogenous leukemia (CML) CD34(+) cell proliferation mostly depends on the nucleo-cytoplasmic ratio of the cyclin-dependent kinase inhibitor p27. The ubiquitin-ligase SCF(Skp2) promotes degradation of phosphorylated p27 at T187 in the nucleus, resulting in G1/S progression of the cells. On the other hand, phosphatidylinositol-3-kinase (PI3K)-directed T157 nuclear localization signal (NLS) phosphorylation results in cytoplasmic sequestration of p27, leading to abnormal integrin-mediated proliferation of CD34(+) CML cells.

METHODS

We demonstrate the generation of an engineered Epstein-Barr virus (EBV) vector with a BAC backbone that has the unique capacity to carry doubly modified (DM) p27 (i.e. T187A, T157A p27) along with the BCR-ABL siRNA expression construct. The HSV-tk suicide gene has also been incorporated in the same vector, which promotes apoptosis in a BCR-ABL-independent pathway.

RESULTS

Expression of DM p27 markedly inhibits proliferation of BCR-ABL(+) primary human CML cells. Moreover, DM p27 strongly inhibits the growth of imatinib-resistant CML cells, compared to the T157A p27 (SM p27). The CML growth inhibition is found to be the result of significant G1/S arrest with concomitant increase in hypophosphorylated retinoblastoma (Rb). Moreover, the EBV vector mediated stable RNA interference induces apoptosis in K562 cells and reduces myeloid colony forming units.

CONCLUSIONS

We therefore propose a multi-gene delivery strategy for BCR-ABL(+) CML cells by targeting not only the fusion transcript, but also the downstream signaling, to overcome drug resistance in the acute phase of CML.

Critical function for ADAM9 in mouse prostate cancer

ADAM9 is a membrane-anchored metalloprotease that is markedly up-regulated in several human carcinomas. Here, we show that ADAM9 is similarly up-regulated in mouse models for prostate, breast, and intestinal carcinoma. To assess whether ADAM9 is critical for the pathogenesis of prostate carcinoma, one of the most common cancers in men, we evaluated how loss of ADAM9 affects tumorigenesis in W(10) mice, a mouse model for this disease. In the absence of ADAM9, most tumors in 50-week-old W(10) mice were well differentiated, whereas littermate controls expressing wild-type ADAM9 had predominantly poorly differentiated, and in some cases significantly larger, tumors. Moreover, gain-of-function experiments in which ADAM9 was overexpressed in mouse prostate epithelium resulted in significant abnormalities, including epithelial hyperplasia at 4 to 6 months of age, and prostatic intraepithelial neoplasia after 1 year. A potential underlying mechanism for the role of ADAM9 in prostate cancer emerged from cell-based assays: ADAM9 can cleave and release epidermal growth factor and FGFR2iiib from cells, both of which have pivotal functions in the pathogenesis of this disease. Taken together, these results suggest that ADAM9 contributes to the pathogenesis of prostate cancer and potentially also other carcinomas, raising the possibility that ADAM9 might be a good target for antitumor drugs.