Deregulation of p27 by oncogenic signaling and its prognostic significance in breast cancer

Presence of HER4 associates with increased sensitivity to Herceptin in patients with metastatic breast cancer

INTRODUCTION

HER2 overexpression, or rather HER2 gene amplification, is indicative for Herceptin therapy in both metastatic and pre-metastatic breast cancer patients. Patient's individual sensitivity to Herceptin treatment, however, varies enormously and spans from effectual responsiveness over acquired insensitivity to complete resistance from the outset. Thus no predictive information can be deduced from HER2 determination so that molecular biomarkers indicative for Herceptin sensitivity or resistance need to be identified. Both ErbB receptor-dependent signalling molecules as well as HER2-related ErbB receptor tyrosine kinases, known to mutually interact and to cross-regulate each other are prime candidates to be involved in cellular susceptibility to Herceptin.

METHODS

Using immunohistochemistry and fluorescence in situ hybridisation, we retrospectively investigated primary breast cancer tissues from 48 patients who were under Herceptin treatment. We quantified the gene copy numbers of all HER receptors and evaluated their coexpression profile. Moreover the HER2 phosphorylation state, the ratio of native to truncated HER2, p27(kip1) and PTEN expression were objects of this study.

RESULTS

Above all markers investigated in this study Kaplan-Meier and Cox regression analysis revealed a significant positive impact of HER4 (co-)expression on overall survival from beginning of antibody therapy. Both HER4 expression and HER4 gene amplification emerged as independent prognostic markers in Herceptin-treated breast cancer patients and responsiveness to Herceptin turned out to be more efficient if tumour cells show HER4 expression.

CONCLUSIONS

Although HER4 is known to potentially exert a tumour cell killing activity and in turn to have a favourable impact in breast cancer patients we demonstrate here the first time that HER4 expression prolongs overall survival in Herceptin-treated patients. Elucidating HER4 receptor function in the context of Herceptin treatment will advance the design of highly efficient receptor targeting. By then we need to extend the analysis of breast cancer by allowing for HER2/HER4 coexpression by which valuable additional prognostic and predictive information might possibly be revealed.

Polymorphic loci of E2F2, CCND1 and CCND3 are associated with HER2 status of breast tumors

Overexpression of the human epidermal growth factor receptor 2 (HER2) in breast tumors is associated with bad prognosis. Therefore, it is highly relevant to further improve understanding of the regulatory mechanisms of HER2 expression. In addition to gene amplification, transcriptional regulation plays a crucial role in HER2 overexpression. In this study, we analyzed 3 polymorphisms E2F2_-5368_A>G, CCND1_870_A>G and CCND3_-677_C>T located in genes involved in cell cycle regulation in the GENICA population-based and age-matched breast cancer case-control study from Germany. We genotyped 1,021 cases and 1,015 controls by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Statistical analyses were performed by conditional logistic regression. We observed no differences in genotype frequencies between breast cancer cases and controls. Subgroup analysis showed associations between carriers of the E2F2_-5368_G allele (OR: 0.60, 95% CI: 0.42-0.85), carriers of the CCND1_870_G allele (OR: 0.66, 95% CI: 0.45-0.96) and carriers of the CCND3_-677_T allele (OR: 1.72, 95% CI: 1.20-2.49) and HER2 expression in breast tumors. This finding points to an association of an increased expression of these cell cycle regulators with lower expression of HER2. An explanation for this observation might be that low expression of E2F2, CCND1 and CCND3 decrease levels of factors down-regulating HER2. We conclude that the analyzed polymorphisms located in E2F2, CCND1 and CCND3 are potential markers for HER2 status of breast tumors.

Stemming resistance to HER-2 targeted therapy

Although the development of trastuzumab and lapatinib has improved the outlook for women with HER-2 positive breast cancer, resistance to HER-2 targeted therapy is a growing clinical dilemma. Recent evidence indicates that the HER-2 pathway may play an important role in the maintenance of cancer stem cells (CSCs). The success of HER-2 targeted therapies may, in part, be explained by their direct activity against HER-2 positive CSCs. Our understanding of the mechanisms involved in resistance to trastuzumab, including loss or blockade of the trastuzumab binding site, activation of alternative signaling pathways, and induction of epithelial-mesenchymal transition (EMT), suggests that CSCs may be at the root of resistance of HER-2 targeted therapy. A variety of novel HER-2 targeted approaches have demonstrated promising preliminary clinical activity. Future clinical trials should involve the integration of technologies to assess the impact of novel HER-2 targeted therapies on HER-2 positive CSCs.

EGCG stabilizes p27kip1 in E2-stimulated MCF-7 cells through down-regulation of the Skp2 protein

Loss of p27Kip1 is associated with a poor prognosis in breast cancer. According to previous findings, a decrease in p27Kip1 levels is mainly the result of enhanced proteasome-dependent degradation mediated by its specific ubiquitin ligase subunit S-phase kinase protein 2 (Skp2). Epigallocatechin-3-gallate (EGCG), the main constituent of green tea, was found to stabilize p27Kip1 levels in breast cancer, but whether this effect is mediated through changes in Skp2 expression remains unclear. Here we investigated the mechanisms involved in EGCG's growth inhibition of estrogen-responsive human breast cancer MCF-7 cells. In our results, EGCG increased p27Kip1 and decreased Skp2 in a time- and dose-dependent manner, suggesting that p27Kip1 and Skp2 may be involved in the growth inhibition by EGCG in estrogen-stimulated MCF-7 cells. Interestingly, mRNA levels of p27Kip1 and Skp2 did not significantly change in estrogen-stimulated MCF-7 cells after EGCG treatments. Moreover, overexpression of Skp2 in MCF-7 cells prevented accumulation of p27Kip1 and promoted resistance to the antiproliferative effects of EGCG. This suggests that the down-regulation of the F-box protein Skp2 is the mechanism underlying p27Kip1 accumulation. Furthermore, both tamoxifen and paclitaxel significantly and synergistically enhanced the growth inhibition of MCF-7 cells by EGCG through the down-regulation of Skp2 protein. However, the down-regulation of Skp2 was not always correlate with the up-regulation of p27, suggesting that EGCG-dependent Skp2 down-regulation can influence cell growth in several ways. The therapeutic strategies designed to reduce Skp2 may therefore play an important clinical role in treatment of breast cancer cells.

Effects of common germline genetic variation in cell cycle control genes on breast cancer survival: results from a population-based cohort

INTRODUCTION

Somatic alterations have been shown to correlate with breast cancer prognosis and survival, but less is known about the effects of common inherited genetic variation. Of particular interest are genes involved in cell cycle pathways, which regulate cell division.

METHODS

We examined associations between common germline genetic variation in 13 genes involved in cell cycle control (CCND1, CCND2, CCND3, CCNE1, CDK2 [p33], CDK4, CDK6, CDKN1A [p21, Cip1], CDKN1B [p27, Kip1], CDKN2A [p16], CDKN2B [p15], CDKN2C [p18], and CDKN2D [p19]) and survival among women diagnosed with invasive breast cancer participating in the SEARCH (Studies of Epidemiology and Risk factors in Cancer Heredity) breast cancer study. DNA from up to 4,470 women was genotyped for 85 polymorphisms that tag the known common polymorphisms (minor allele frequency > 0.05) in the genes. The genotypes of each polymorphism were tested for association with survival using Cox regression analysis.

RESULTS

The rare allele of the tagging single nucleotide polymorphism (SNP) rs2479717 is associated with an increased risk of death (hazard ratio = 1.26 per rare allele carried, 95% confidence interval: 1.12 to 1.42; P = 0.0001), which was not attenuated after adjusting for tumour stage, grade, and treatment. This SNP is part of a large linkage disequilibrium block, which contains CCND3, BYSL, TRFP, USP49, C6ofr49, FRS3, and PGC. We evaluated the association of survival and somatic expression of these genes in breast tumours using expression microarray data from seven published datasets. Elevated expression of the C6orf49 transcript was associated with breast cancer survival, adding biological interest to the finding.

CONCLUSION

It is possible that CCND3 rs2479717, or another variant it tags, is associated with prognosis after a diagnosis of breast cancer. Further study is required to validate this finding.

Endothelin-1 couples betaPix to p66Shc: role of betaPix in cell proliferation through FOXO3a phosphorylation and p27kip1 down-regulation independently of Akt

The phosphorylation of forkhead transcription factor FOXO3a by Akt is critical regulator of cell proliferation induced by serum. We show that endothelin-1 (ET-1) stimulation of primary human mesangial cells (HMCs) induces betaPix and p66Shc up-regulation, resulting in the formation of the betaPix/p66Shc complex. In transformed HMCs, ET-1 induces a biphasic phosphorylation of p66Shc and FOXO3a. The second phase leads to p27(kip1) down-regulation independently of Akt. Depletion of betaPix blocks the second phase of p66Shc and FOXO3a phosphorylation and prevents p27(kip1) down-regulation induced by ET-1. Depletion of either betaPix or p66Shc inhibits ET-1-induced cell proliferation. The expression of beta(1)Pix induces FOXO3a phosphorylation through activation of Rac1, ERK1/2, and p66Shc. Using either p66Shc- or Akt-depleted cells; we show that beta(1)Pix-induced FOXO3a phosphorylation requires p66Shc but not Akt. beta(1)Pix-induced p27(kip1) down-regulation was blocked by U0126 but not by wortmannin. Endogenous betaPix and FOXO3a are constitutively associated with endogenous p66Shc. FOXO3a and p66Shc binding requires beta(1)Pix homodimerization. Expression of beta(1)Pix homodimerization deficient mutant abrogates beta(1)Pix-induced p27(kip1) down-regulation and cell proliferation. Our results identify p66Shc and FOXO3a as novel partners of beta(1)Pix and represent the first direct evidence of beta(1)Pix in cell proliferation via Erk/p66Shc-dependent and Akt-independent mechanisms.

Cell cycle machinery: links with genesis and treatment of breast cancer

Loss of normal growth control is a hallmark of cancer. Thus, understanding the mechanisms of tissue-specific, normal growth regulation and the changes that occur during tumorigenesis may provide insights of both diagnostic and therapeutic importance. Control of cell proliferation in the normal mammary gland is steroid hormone (estrogen and progestin)-dependent, involves complex interactions with other hormones, growth factors and cytokines and ultimately converges on activation of three proto-oncogenes (c-Myc, cyclin D1 and cyclin E1) that are rate limiting for the G1 to S phase transition during normal cell cycle progression. Mammary epithelial cell-specific overexpression of these genes induces mammary carcinoma in mice, while cyclin D1 null mice have arrested mammary gland development and are resistant to carcinoma induced by the neu/erbB2 and ras oncogenes. Furthermore, c-Myc, cyclins D1, E1 and E2 are commonly overexpressed in primary breast cancer where elevated expression is often associated with a more aggressive disease phenotype and an adverse patient outcome. This may be due in part to overexpression of these genes conferring resistance to endocrine therapies since in vitro studies provide compelling evidence that overexpression of c-Myc and to a lesser extent cyclin D1 and cyclin E1, attenuate the growth inhibitory effects of SERMS, antiestrogens and progestins in breast cancer cells. Thus, abnormal regulation of the expression of cell cycle molecules, involved in the steroidal control of cell proliferation in the mammary gland, are likely to be directly involved in the development, progression and therapeutic responsiveness of breast cancer. Furthermore, a more detailed understanding of these pathways may identify new targets for therapeutic intervention particularly in endocrine-unresponsive and endocrine-resistant disease.

Overview of resistance to systemic therapy in patients with breast cancer

Breast cancer is the most common cancer and the second leading cause of cancer death in American women. It was the second most common cancer in the world in 2002, with more than 1 million new cases. Despite advances in early detection and the understanding of the molecular bases of breast cancer biology, about 30% of patients with early-stage breast cancer have recurrent disease. To offer more effective and less toxic treatment, selecting therapies requires considering the patient and the clinical and molecular characteristics of the tumor. Systemic treatment of breast cancer includes cytotoxic, hormonal, and immunotherapeutic agents. These medications are used in the adjuvant, neoadjuvant, and metastatic settings. In general, systemic agents are active at the beginning of therapy in 90% of primary breast cancers and 50% of metastases. However, after a variable period of time, progression occurs. At that point, resistance to therapy is not only common but expected. Herein we review general mechanisms of drug resistance, including multidrug resistance by P-glycoprotein and the multidrug resistance protein family in association with specific agents and their metabolism, emergence of refractory tumors associated with multiple resistance mechanisms, and resistance factors unique to host-tumor-drug interactions. Important anticancer agents specific to breast cancer are described. Breast cancer is the most common type of cancer and the second leading cause of cancer death in American women. In 2002, 209,995 new cases of breast cancer were registered, and 42,913 patients died of it. In 5 years, the annual prevalence of breast cancer will reach 968,731 cases in the United States. World wide, the problem is just as significant, as breast cancer is the most frequent cancer after nonmelanoma skin cancer, with more than 1 million new cases in 2002 and an expected annual prevalence of more than 4.4 million in 5 years. Breast cancer treatment currently requires the joint efforts of a multidisciplinary team. The alternatives for treatment are constantly expanding. With the use of new effective chemotherapy, hormone therapy, and biological agents and with information regarding more effective ways to integrate systemic therapy, surgery, and radiation therapy, elaborating an appropriate treatment plan is becoming more complex. Developing such a plan should be based on knowledge of the benefits and potential acute and late toxic effects of each of the therapy regimens. Despite advances in early detection and understanding of the molecular bases of breast cancer biology, approximately 30% of all patients with early-stage breast cancer have recurrent disease, which is metastatic in most cases. The rates of local and systemic recurrence vary within different series, but in general, distant recurrences are dominant, strengthening the hypothesis that breast cancer is a systemic disease from presentation. On the other hand, local recurrence may signal a posterior systemic relapse in a considerable number of patients within 2 to 5 years after completion of treatment. To offer better treatment with increased efficacy and low toxicity, selecting therapies based on the patient and the clinical and molecular characteristics of the tumor is necessary. Consideration of these factors should be incorporated in clinical practice after appropriate validation studies are performed to avoid confounding results, making them true prognostic and predictive factors. A prognostic factor is a measurable clinical or biological characteristic associated with a disease-free or overall survival period in the absence of adjuvant therapy, whereas a predictive factor is any measurable characteristic associated with a response or lack of a response to a specific treatment. The main prognostic factors associated with breast cancer are the number of lymph nodes involved, tumor size, histological grade, and hormone receptor status, the first two of which are the basis for the AJCC staging system. The sixth edition of the American Joint Committee on Cancer staging system allows better prediction of prognosis by stage. However, after determining the stage, histological grade, and hormone receptor status, the tumor can behave in an unexpected manner, and the prognosis can vary. Other prognostic and predictive factors have been studied in an effort to explain this phenomenon, some of which are more relevant than others: HER-2/neu gene amplification and protein expression, expression of other members of the epithelial growth factor receptor family, S phase fraction, DNA ploidy, p53 gene mutations, cyclin E, p27 dysregulation, the presence of tumor cells in the circulation or bone marrow, and perineural and lymphovascular space invasion. Systemic treatment of breast cancer includes the use of cytotoxic, hormonal, and immunotherapeutic agents. All of these agents are used in the adjuvant, neoadjuvant, and metastatic setting. Adjuvant systemic therapy is used in patients after they undergo primary surgical resection of their breast tumor and axillary nodes and who have a significant risk of systemic recurrence. Multiple studies have demonstrated that adjuvant therapy for early-stage breast cancer produces a 23% or greater improvement in disease-free survival and a 15% or greater increase in overall survival rates. Recommendations for the use of adjuvant therapy are based on the individual patient's risk and the balance between absolute benefit and toxicity. Anthracycline-based regimens are preferred, and the addition of taxanes increases the survival rate in patients with lymph node-positive disease. Adjuvant hormone therapy accounts for almost two thirds of the benefit of adjuvant therapy overall in patients with hormone-receptor-positive breast cancer. Tamoxifen is considered the standard of care in premenopausal patients. In comparison, the aromatase inhibitor anastrozole has been proven to be superior to tamoxifen in postmenopausal patients with early-stage breast cancer. The adjuvant use of monoclonal antibodies and targeted therapies other than hormone therapy is being studied. Interestingly, some patients have an early recurrence even though they have a tumor with good prognostic features and at a favorable stage. These recurrences have been explained by the existence of certain cellular characteristics at the molecular level that make the tumor cells resistant to therapy. Selection of resistant cell clones of micrometastatic disease has also been proposed as an explanation for these events. Neoadjuvant systemic therapy, which is the standard of care for patients with locally advanced and inflammatory breast cancer, is becoming more popular. It reduces the tumor volume, thus increasing the possibility of breast conservation, and at the same time allows identification of in vivo tumor sensitivity to different agents. The pathological response to neoadj uvant systemic therapy in the breast and lymph nodes correlates with patient survival. Use of this treatment modality produces survival rates identical to those obtained with the standard adjuvant approach. The rates of pathological complete response (pCR) to neoadjuvant systemic therapy vary according to the regimen used, ranging from 6% to 15% with anthracycline-based regimens to almost 30% with the addition of a noncross-resistant agent such as a taxane. In one study, the addition of neoadjuvant trastuzumab in patients with HER-2-positive breast tumors increased the pCR rate to 65%. Primary hormone therapy has also been used in the neoadjuvant systemic setting. Although the pCR rates with this therapy are low, it significantly increases breast conservation. Currently, neoadjuvant systemic therapy is an important tool in not only assessing tumor response to an agent but also studying the mechanisms of action of the agent and its effects at the cellular level. However, no tumor response is observed in some cases despite the use of appropriate therapy. The tumor continues growing during treatment in such cases, a phenomenon called primary resistance to therapy. The use of palliative systemic therapy for metastatic breast cancer is challenging. Five percent of newly diagnosed cases of breast cancer are metastatic, and 30% of treated patients have a systemic recurrence. Once metastatic disease develops, the possibility of a cure is very limited or practically nonexistent. In this heterogeneous group of patients, the 5-year survival rate is 20%, and the median survival duration varies from 12 to 24 months. In this setting, breast cancer has multiple clinical presentations, and the therapy for it should be chosen according to the patient's tumor characteristics, previous treatment, and performance status with the goal of improving survival without compromising quality of life. Treatment resistance is most commonly seen in such patients. They initially may have a response to different agents, but the responses are not sustained, and, in general, the rates of response to subsequent agents are lower. Table 1 summarizes metastatic breast cancer response rates to single-agent systemic therapy.

Relocalized p27Kip1 tumor suppressor functions as a cytoplasmic metastatic oncogene in melanoma

The p27 tumor suppressor negatively regulates G1 cell cycle progression. However, human malignancies rarely select for deletion/inactivation of p27, a hallmark of tumor suppressor genes. Instead, p27 is degraded or relocalized to the cytoplasm in aggressive malignancies, supporting the notion that p27 sequestration from its nuclear cyclin:cyclin-dependent kinase (cdk) targets is critical. However, emerging cell biology data suggest a novel cdk-independent cytoplasmic function of p27 in cell migration. Here, we find cytoplasmic p27 in 70% of invasive and metastatic melanomas. In contrast, no cytoplasmic p27 was detected in noninvasive, basement membrane-confined melanoma in situ, suggesting a late oncogenic role for cytoplasmic p27 in metastasis. Targeted cytoplasmic expression of wild-type or non-cdk-binding p27 at subphysiologic levels induced melanoma motility and resulted in numerous metastases to lymph node, lung, and peritoneum. These observations point to a prominent role of cytoplasmic p27 in metastatic disease that is independent of cyclin:cdk regulation or mere nuclear loss.

Mechanism of the anti-cancer activity of Zizyphus jujuba in HepG2 cells

The Zizyphus jujuba fruit has been used as a traditional Chinese medicinal herb and considered to affect various physiological functions in the body for thousands of years. However, its anti-cancer activity and mechanism of action remain to be elucidated. We investigated the anti-cancer activity of Zizyphus jujuba Mill and its underlining mechanisms of action in human hepatoma cells (HepG2) and found that the extract of Z. jujuba decreased the viability of the cells. Further extraction of the initial Z. jujuba extract with organic solvents revealed that the chloroform fraction (CHCl(3)-F) was the most effective. Interestingly, the CHCl(3)-F induced not only apoptosis but also G1 arrest at a low concentration (100 mug/ml) and G2/M arrest at a higher concentration (200 mug/ml) by cell cycle assay. Apoptosis, an increase in intracellular ROS (reactive oxygen species) level, a decline of mitochondrial membrane potential at low Z. jujuba concentrations, and a ROS-independent mitochondrial dysfunction pathway at high concentrations were all observed. CHCl(3)-F-induced G1 arrest in HepG2 cells was associated with an increase in hypohosphorylation of Rb and p27(Kip1), and a decrease of phosphorylated Rb. However, CHCl(3)-F-induced G2/M arrest in HepG2 cells correlated with a decrease of the p27(Kip1) levels and generation of the phosphorylation of p27(Kip1), however the hypohosphorylation of Rb protein remained. Collectively, our findings suggest that the CHCl(3)-F extract of Z. jujuba extract induced a concentration dependent effect on apoptosis and a differential cell cycle arrest in HepG2 cells.

Polymorphisms cMyc-N11S and p27-V109G and breast cancer risk and prognosis

BACKGROUND

cMyc and p27 are key genes implicated in carcinogenesis. Whether polymorphisms in these genes affect breast cancer risk or prognosis is still unclear. In this study, we focus on a rare non-synonymous polymorphism in cMyc (N11S) and a common polymorphism in p27 (V109G) and determine their role in risk and prognosis using data collected from the Ontario Breast Cancer Family Registry.

METHODS

Risk factor data was collected at baseline on a large group of women (cases = 1,115 and population-based controls = 710) and clinical data (including treatment and follow-up) were collected prospectively by periodic review of medical records for a subset of cases (N = 967) for nearly a decade. A centralized pathology review was conducted. Unconditional logistic regression was used to determine the association of polymorphisms with breast cancer risk and the Cox proportional hazards model was used to determine their association with survival.

RESULTS

Our results suggest that while cMyc-N11S can be considered a putatively functional polymorphism located in the N-terminal domain, it is not associated with risk, tumor characteristics or survival. The p27-G109 allele was associated with a modest protective effect in adjusted analyses and higher T stage. We found no evidence to suggest that p27-V109G alone or in combination with cMyc-N11S was associated with survival. Age at onset and first-degree family history of breast or ovarian cancer did not significantly modify the association of these polymorphisms with breast cancer risk.

CONCLUSION

Further work is recommended to understand the potential functional role of these specific non-synonymous amino acid changes and a larger, more comprehensive investigation of genetic variation in these genes (e.g., using a tagSNP approach) in combination with other relevant genes is needed as well as consideration for treatment effects when assessing their potential role in prognosis.

Human pheochromocytomas show reduced p27Kip1 expression that is not associated with somatic gene mutations and rarely with deletions

Pheochromocytomas are neuroendocrine tumors arising in the neural crest-derived chromaffin cells of the adrenal gland or in extra-adrenal sympathetic ganglia (paragangliomas). In a rat model of multiple endocrine neoplasia (MEN), absence of functional p27Kip1 protein predisposes to pheochromocytoma and paraganglioma development. As no data is available regarding the involvement of p27Kip1 in human pheochromocytoma and/or paraganglioma, we set out to determine the expression pattern of p27Kip1 in those tumor types. A panel of 25 pheochromocytomas and 23 paragangliomas was collected. Two pheochromocytomas were from MEN2 patients. The paragangliomas included 15 tumors that developed at the carotid bifurcation, three in the jugulo-tympanic area, and five at other sites. Except for the MEN2 cases, all others were apparently sporadic. Immunohistochemistry for p27Kip1 and the proliferation marker Ki67 was performed. We found that p27Kip1 expression is reduced/lost in 56% of pheochromocytomas, but only in 18.1% of paragangliomas. Downregulation of p27Kip1 was not associated with increased proliferation. Cases showing reduced/lost p27Kip1 expression were screened for the presence of somatic mutations in CDKN1B (p27Kip1) and for allelic imbalance at the p27Kip1 locus. Three cases had allelic imbalance but none had mutations. In conclusion, pheochromocytomas display extreme reduction/loss of p27Kip1 expression at high frequency.

Prognostic significance of p27Kip1 expression in bladder cancer

The importance of markers in urological cancer is well recognised and many attempts are being made to find one which will be of prognostic significance. Authors from New York found that low expression of p27Kip1 in patients with bladder cancer was a significant predictor of pelvic recurrence, progression to metastasis and death. Authors from Switzerland examined patients with a primary solitary distal ureteric TCC; they found that distal ureteric resection in such patients is feasible, and that the long-term oncological outcome appears to be comparable to more radical treatment of this condition.

OBJECTIVE

To define the prognostic significance of p27(Kip1) expression in bladder cancer for overall, disease-specific, metastasis-free and pelvic recurrence-free survival, and to identify clinical and pathological correlates of p27(Kip1) immunophenotypes.

PATIENTS AND METHODS

Tumour samples from 128 evaluable patients with bladder cancer were assessed by immunohistochemistry for p27(Kip1) and E2F-1 expression. Immunoreactivity of p27(Kip1) was correlated with clinicopathological variables, E2F-1 immunoreactivity, and outcome. Multivariate analysis was used to assess predictors of outcome. The median follow-up was 30.9 months overall and 105.7 months in the 32 patients alive at the last follow-up.

RESULTS

The fraction of tumour cells with p27(Kip1) nuclear immunoreactivity was <5% in 15, 5-25% in 30, 25-50% in 19, 50-75% in 51, and > or = 75% in 13 patients. High-grade tumours and those with lower E2F-1 nuclear reactivity had a lower mean percentage p27(Kip1) reactivity (P = 0.047 and 0.011, respectively). On multivariate analysis, the percentage p27(Kip1) reactivity was a significant independent predictor of pelvic recurrence (P = 0.017), progression to metastases (P = 0.046), death from disease (P = 0.008), and death from any cause (P = 0.017), with a low expression portending a worse prognosis. Suspicion of vascular invasion was a significant independent predictor of progression to metastases (P = 0.002), death from disease, and death from any cause (both P < 0.001). Lymph node involvement was a significant independent predictor of progression to metastases (P = 0.006).

CONCLUSIONS

Low expression of p27(Kip1) was a significant independent predictor of pelvic recurrence, progression to metastasis, death from disease and death from any cause, in patients with bladder cancer.

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.

Characterization of columnar cell lesions of the breast: immunophenotypic analysis of columnar alteration of lobules with prominent apical snouts and secretions

Columnar cell lesions of the breast are detected with increasing frequency in routine pathology practice, in part as a result of the widespread biopsy of nonpalpable breast abnormalities detected by screening mammography. Immunohistochemical investigation of the lesions in relation to the normal breast or to other breast pathologies is not well characterized, and the malignant potential of this spectrum of lesions has not been examined clinically. In this study, a cohort of 45 breast specimens containing columnar cell lesions, in particular, columnar alteration of lobules with prominent apical snouts and secretions (CAPSS), was investigated for expression of a series of breast tumor biomarkers. Using a semiquantitative immunohistochemical scoring system, up-regulation of estrogen, progesterone, and androgen receptors in CAPSS lesions to levels not significantly different from that in in situ or invasive breast tumors was identified. In four cases where CAPSS within a specimen lacked expression of a steroid hormone receptor, the coexisting in situ or invasive carcinoma also lacked expression of that receptor. In 81% of CAPSS lesions, E-cadherin immunostaining was reduced in isolated foci of cells or was decreased in intensity in all cells within the lesion. Quantitation of Ki-67 immunostaining demonstrated that proliferation of cells within CAPSS lesions was increased, compared with normal breast epithelium, but was lower than that detected in in situ or invasive cancers within the same specimens. Results of these analyses indicate that CAPSS shares immunophenotypic alterations with other premalignant lesions, the clinical implications of which may be investigated using established breast tumor biomarkers.

Targeting the ubiquitin-proteasome pathway in breast cancer therapy

The ubiquitin-proteasome pathway (UPP) is the major eukaryotic mechanism for regulated intracellular proteolysis. Targeting this pathway with proteasome inhibitors has been validated as a rational strategy against hematologic malignancies, but for most solid tumor populations, including breast cancer, such agents have not shown encouraging activity. However, there is an increasing body of evidence showing that UPP dysregulation plays an important role in mammary tumorigenesis. Moreover, modulation of ubiquitin-proteasome function is emerging as a rational strategy to enhance chemosensitivity and overcome chemoresistance. Taken together, these facts suggest that we are only beginning to appreciate the relevance of this pathway for the current and future therapy of patients with breast cancer. This review provides an overview of the biology of the UPP, its role in the malignant process, the current state of knowledge regarding clinical heat shock protein and proteasome inhibition, and some likely future directions that may enhance our ability to exploit this pathway therapeutically.

Semi-quantitative scoring of potentially predictive markers for endocrine treatment of breast cancer: a comparison between whole sections and tissue microarrays

AIM

To assess whether immunohistochemically stained tissue microarrays (TMA) of 2 mm cores from paraffin embedded tumour tissue may replace whole sections in semi-quantitative evaluation of selected potential markers for endocrine treatment.

METHODS

Whole sections and 2 mm cores on TMA were used for immunohistochemical staining of potential markers for endocrine treatment. The Allred scoring system was used for the markers with nuclear localisation: the oestrogen receptor, the progesterone receptor, p27 and the oestrogen receptor co-regulator amplified in breast cancer 1 (AIB1). The Allred scoring system was also used for the non-nuclear markers Bcl-2, pS2 and cyclooxygenase 2 (COX-2); the membrane receptors HER-2, insulin-like growth factor I receptor (IGF-IR) and epidermal growth factor receptor were quantified according to the guidelines for the Herceptest.

RESULTS

The data and statistical analyses showed that the semi-quantitative evaluation of oestrogen receptor, progesterone receptor, AIB1, COX-2, HER-2 and IGF-IR on TMA blocks was comparable with analysis on whole sections.

CONCLUSIONS

This study shows that semi-quantitative scoring of 2 mm cores on TMA is feasible for several potential markers for endocrine therapy. Considering the small size of many breast tumours, the speed and cost-effectiveness of immunohistochemistry on TMA compared with whole sections, and the importance of the expression level of the proteins, semi-quantitative scoring on TMA has great potential in both retrospective and prospective studies aiming at improving the prediction of response to endocrine treatment.

PI3K/Akt signaling regulates p27(kip1) expression via Skp2 in PC3 and DU145 prostate cancer cells, but is not a major factor in p27(kip1) regulation in LNCaP and PC346 cells

BACKGROUND

We compared the involvement of PI3K/PTEN/Akt signaling in the regulation of the cell-cycle regulator p27(kip1) and investigated the mechanism of PI3K/PTEN/Akt modulation of p27(kip1) in the prostate cancer cell lines LNCaP, PC346, PC3, and DU145.

METHODS

PI3K/PTEN/Akt signaling was manipulated by wortmannin or specific siRNA. The effects on PI3K/Akt downstream effectors and p27(kip1) expression were monitored on RNA and protein levels.

RESULTS

PI3K/Akt inhibition in LNCaP and PC346 cells hardly affected p27(kip1) expression. As shown in LNCaP cells, p27(kip1) expression inversely correlated with Skp2 expression, but Skp2 was not regulated by Akt. Blocking PI3K/Akt signaling in PC3 cells resulted in decreased Skp2 protein expression and increased p27(kip1). Downregulation of PTEN in DU145 cells also showed PTEN/Akt-dependent regulation of Skp2 and p27(kip1).

CONCLUSIONS

In PC3 and DU145 cells, Skp2 is the main determinant in the PI3K/Akt-dependent regulation of p27(kip1). In LNCaP and PC346 cells, PI3K/Akt signaling is not a major factor in p27(kip1) regulation.

Effect of p27(KIP1) on cell cycle and apoptosis in gastric cancer cells

AIM

To elucidate the effect of p27(KIP1) on cell cycle and apoptosis regulation in gastric carcinoma cells.

METHODS

The whole length of p27(KIP1) cDNA was transfected into human gastric cancer cell line SCG7901 by lipofectamine. Expression of p27(KIP1) protein or mRNA was analyzed by Western blot and RNA dot blotting, respectively. Effect of p27(KIP1) on cell growth was observed by MTT assay and anchorage-independent growth in soft agar. Tumorigenicity in nude mice was used to assess the in vivo biological effect of p27(KIP1). Flow cytometry, TUNEL, and electron microscopy were used to assess the effect of p27(KIP1) on cell cycle and apoptosis.

RESULTS

Expression of p27(KIP1) protein or mRNA increased evidently in SCG7901 cells transfected with p27(KIP1). The cell growth was reduced by 31% at 48 h after induction with zinc determined by cell viability assay. The alteration of cell malignant phenotype was evidently indicated by the loss of anchorage-independent growth ability in soft agar. The tumorigenicity in nude mice was reduced evidently (0.55+/-0.14 cm vs 1.36+/-0.13 cm, P<0.01). p27(KIP1) overexpression caused cell arrest with 36% increase (from 33.7% to 69.3%, P<0.01) in G1 population. Prolonged p27(KIP1) expression induced apoptotic cell death reflected by pre-G1 peak in the histogram of FACS, which was also confirmed by TUNEL assay and electron microscopy.

CONCLUSION

p27(KIP1) can prolong cell cycle in G1 phase and lead to apoptosis. p27(KIP1) may be a good candidate for cancer gene therapy.

Tamoxifen may prevent both ER+ and ER- breast cancers and select for ER- carcinogenesis: an alternative hypothesis

INTRODUCTION

Breast Cancer Prevention Trial (BCPT) and Multiple Outcomes of Raloxifene (MORE) data have been interpreted to indicate that tamoxifen reduces the risk of ER+ but not ER- breast carcinogenesis. We explored whether these data also support an alternative hypothesis, that tamoxifen influences the natural history of both ER+ and ER- cancers, that it may be equally effective in abrogating or delaying ER- and ER+ carcinogenesis, and place selection pressure, in some cases, for the outgrowth of ER- cancers.

METHODS

BCPT and MORE data were used to investigate whether: first, tamoxifen could reduce equally the emergence of ER- and ER+ tumors; and second, tamoxifen could select a fraction of emerging ER+ cancers and promote their transformation to ER- cancers. Assuming that some proportion, Z, of ER+ tumors becomes ER- after tamoxifen exposure and that the risk reduction for both ER- and ER+ tumors is equal, we solved for both the transformation rate and the risk reduction rate.

RESULTS

If tamoxifen equally reduces the incidence of ER+ and ER- tumors by 60%, the BCPT results are achieved with a transformation of approximately Z = 20% of ER+ to ER- tumors. Validation with MORE data using an equal risk reduction of 60% associated with tamoxifen produces an almost identical transformation rate Z of 23%.

CONCLUSION

Data support an alternative hypothesis that tamoxifen may promote ER- carcinogenesis from a precursor lesion that would otherwise have developed as ER+ without tamoxifen selection.

The tumor suppressors Ink4c and p53 collaborate independently with Patched to suppress medulloblastoma formation

Recurrent genetic alterations in human medulloblastoma (MB) include mutations in the sonic hedgehog (SHH) signaling pathway and TP53 inactivation (approximately 25% and 10% of cases, respectively). However, mouse models of MB, regardless of their initiating lesions, generally depend upon p53 inactivation for rapid onset and high penetrance. The gene encoding the cyclin-dependent kinase inhibitor p18(Ink4c) is transiently expressed in mouse cerebellar granule neuronal precursor cells (GNPs) as they exit the cell division cycle and differentiate. Coinactivation of Ink4c and p53 provided cultured GNPs with an additive proliferative advantage, either in the presence or absence of Shh, and induced MB with low penetrance but with greatly increased incidence following postnatal irradiation. In contrast, mice lacking one or two functional Ink4c alleles and one copy of Patched (Ptc1) encoding the Shh receptor rapidly developed MBs that retained wild-type p53. In tumor cells purified from double heterozygotes, the wild-type Ptc1 allele, but not Ink4c, was inactivated. Therefore, when combined with Ptc1 mutation, Ink4c is haploinsufficient for tumor suppression. Methylation of INK4C (CDKN2C) was observed in four of 23 human MBs, and p18(INK4C) protein expression was extinguished in 14 of 73 cases. Hence, p18(INK4C) loss may contribute to MB formation in children.

Paclitaxel and carboplatin as first-line chemotherapy combined with gefitinib (IRESSA) in patients with advanced breast cancer: a phase I/II study conducted by the Hellenic Cooperative Oncology Group

Paclitaxel (Taxol) and carboplatin are an effective combination regimen for treating advanced breast cancer. Gefitinib (IRESSA) is the first epidermal growth factor receptor tyrosine kinase inhibitor to be approved for cancer treatment. This multicenter phase II trial treated 68 patients with advanced breast cancer with paclitaxel (175 mg/m(2) over 3 h) and 3-weekly carboplatin (area under the curve of 6) for six cycles, and 250 mg/day gefitinib orally. Median age was 57 (range 35-77) years, patients had performance status 0 (69.1%), 1 (27.9%) 2 (2.9%), 82.4% of patients had visceral metastases and 63.2% had received adjuvant chemotherapy. Forty-eight (70.6%) patients completed six cycles of chemotherapy and 20 (29.4%) patients discontinued treatment (seven [10.3%] due to disease progression, seven [10.3%] due to toxicity, five [7.4%] withdrew consent and one [1.5%] died after the first cycle). Sixty-three (92.7%) patients were evaluable for response; nine (13.2%) had complete responses, 30 (44.1%) had partial responses, 21 (30.9%) had stable disease and three (4.4%) had disease progression. Grade 3/4 adverse events in > or =5% of patients except of alopecia, included neutropenia (17.7%), anemia (10.3%), diarrhea (7.4%), thrombocytopenia (5.9%) and peripheral neuropathy (5.9%). Of those tumor biopsies available for immunohistochemical analysis (n=60), 5.0% were positive and 35.0% negative for expression of all HER-family receptors. Comparable numbers of tumor biopsies were nuclear p27(kipl) positive and negative (39.7 and 42.7%, respectively), with the majority (72.1%) negative for cytoplasmic p27(kipl). The observed efficacy data in this study were similar to those reported for the combination of paclitaxel and carboplatin alone.

Potentiation of ceramide-induced apoptosis by p27kip1 overexpression

The cyclin-dependent kinase inhibitor p27kip1 (p27) has been implicated in the regulation of cell cycle and apoptosis. Recently, we have demonstrated that ceramide induces apoptotic cell death associated with increase in the level of p27 in HL-60 cells. In the present study, we showed that overexpression of p27 increases ceramide-induced apoptotic cell death in HL-60 cells. Furthermore, overexpression of p27 accelerated DNA fragmentation, PARP cleavage and cytochrome c release induced by ceramide. In addition, ceramide induced Bax expression independent of p27. These findings indicate that enhanced effect on apoptosis by p27 is associated with mitochondrial signaling which involves cytochrome c release.

Effect of the cyclin-dependent kinases inhibitor p27 on resistance of ovarian cancer multicellular spheroids to anticancer chemotherapy

PURPOSE

A low proliferating fraction in solid tumors limits the effectiveness of cell-cycle-dependent chemotherapeutic agents. To understand the molecular basis of such resistance, we examined the expression of the cyclin-dependent kinases inhibitor p27, and relationship with drug resistance and P-gp expression in ovarian cancer multicellular spheroids.

METHODS

We cultured ovarian cancer cells (A2780 and CAOV3) as multicellular spheroids and examined the expression of p27 and P-glycoprotein (P-gp) by western blot, flow cytometry and confocal. We also analyzed the cell-cycle distribution by flow cytometry. In addition, trypan blue exclusion testing and cell apoptosis analysis were used to detect the sensitivity to Taxol.

RESULTS

When transferred from monolayer to three-dimensional culture, a consistent upregulation of p27 protein and P-gp protein was observed in ovarian cancer cell lines. Compared with monolayer cells, there was a significant increase of G0-G1 phase cells and decrease of S and G2-M phase cells in spheroid cells. Aggregates of cells showed higher cell viability than monolayer cells. Antisense oligodeoxynucleotide (ASON) -mediated downregulation of p27 reduced intercellular adhesion, increased cell proliferation, downregulated P-gp expression and sensitized cells to Taxol.

CONCLUSIONS

Our results implicate that p27 serves as a regulator of drug resistance in ovarian tumors. ASON-mediated alteration of p27 reverses resistance of ovarian cancer to anticancer agents that are associated with increased sensitivity of ovarian cancer cells to chemotherapeutic agents.

Survey of genetically engineered mouse models for prostate cancer: analyzing the molecular basis of prostate cancer development, progression, and metastasis

Genetically engineered mouse models have been generated to study the molecular basis of prostate cancer (PCa) development, progression, and metastasis. Selection of a prostate-specific promoter, such as the probasin (PB) and prostate specific antigen (PSA) promoters, is critical for generating sufficient levels of transgene expression to elicit a phenotypic response. To date, target genes have included growth factors, cell cycle regulators, pro- and anti-apoptotic proteins, steroid hormone and growth factor receptors, oncogenes, tumor suppressors, and homeobox genes. The experimental approaches used to generate these mouse models include overexpression of the transgene, knock-out/knock-in of transgene expression and conditional regulation of expression using Cre/lox technology. This review summarizes the promoters, which have been utilized to create genetically engineered mouse models for PCa. Furthermore, the effects of gene disruption on promoting low- and high-grade intraepithelial neoplasia (LGPIN and HGPIN, respectively), locally invasive carcinoma and metastatic lesions will be discussed. To date, the PB-Cre4 x PTENloxp/loxp model appears to be the only model that represents the entire continuum of prostate adenocarcinoma development, tumor progression, and metastasis, although models that develop prostatic neuroendocrine (NE) cancer can be generated by disrupting one genetic event. Indeed, analysis of bigenic mouse models indicates that two genetic events are generally required for progression from HGPIN to locally invasive adenocarcinoma and that two to five genetic events can promote metastasis to distant sites. Studying the effects of genetic perturbation on PCa biology will increase our understanding of the disease process and potentially provide targets for developing novel therapeutic approaches.

Possible role of Stat5a in rat mammary gland carcinogenesis

Signal transducer and activator of transcription (Stat) 5a is a transcription factor mediating the action of specific cytokines, growth factors and hormones on gene expression. In the mammary gland, Stat5a is well recognized for its function in prolactin signaling, lobuloalveolar development, and milk protein expression during pregnancy and lactation. Latent cytoplasmic Stat5a is activated by tyrosine phosphorylation and following dimerization undergoes nuclear import. In the current study, Stat5a expression was examined immunohistochemically in carcinomas induced by the chemical carcinogens 7,12-dimethylbenz[a]anthracene and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. A high percentage of carcinomas showed nuclear labeling of Stat5a [44 of 68 (65%)] with Stat5a nuclear labeling index ranging from 18 to 77%. In contrast, control normal mammary gland tissue displayed cytosolic expression. Carcinomas with different Stat5a staining patterns (cytoplasmic or nuclear) showed a statistical difference for the proliferating cell nuclear antigen (PCNA) labeling, tumor differentiation, nuclear grade, mitotic activity, and tumor size. High Stat5a nuclear expression was closely correlated with the higher-grade carcinomas. Stat5a nuclear expression was also detected in intraductal proliferations (10 of 21 lesions) and in ductal carcinomas in situ (13 of 15 lesions). Immunohistochemical analysis was further carried out in human breast cancers. Stat5a nuclear expression was detected in ductal and lobular carcinomas and DCIS at a frequency of 48% (15/31), 33% (2/6), and 40% (2/5), respectively. Nuclear expression of Stat5a in human breast cancers also correlated with the PCNA nuclear labeling index. The findings implicate activated Stat5a in mammary gland cancer development in the rat and human.

Expression of protein gene product 9.5 (PGP9.5)/ubiquitin-C-terminal hydrolase 1 (UCHL-1) in human myeloma cells

The neuron cytoplasmic protein gene product 9.5 (PGP9.5)/ubiquitin-C-terminal hydrolase 1 (UCHL-1) protein is a thiol protease that recognizes and hydrolyzes a peptide bond at the C-terminal of ubiquitin, and is involved in the processing of ubiquitin precursors and ubiquinated proteins. Although this molecule is known as a specific tissue marker for the neuroendocrine system, many reports have indicated that PGP9.5 is a marker for certain tumour types, such as cancer of the lung, colon, and pancreas. The expression of PGP9.5 in myeloma cells was examined. PGP9.5 seemed to be expressed specifically in myeloma cells as compared with other haematological malignant cells. In addition, in myeloma cells subjected to growth-factor starvation, the upregulation of PGP9.5 was observed in association with that of p27(Kip1), a cyclin-dependent-kinase inhibitor, although the upregulation caused by irradiation was milder. In contrast, the hypoxic culture of myeloma cells induced down-regulation of PGP9.5. These results suggested that PGP9.5 may be a good marker for myeloma among haematological malignancies. In addition, it may indicate certain cellular features of myeloma cells, such as sensitivity to proteasome inhibitors.

Lactoferrin down-regulates G1 cyclin-dependent kinases during growth arrest of head and neck cancer cells

The molecular mechanism of lactoferrin-induced cell growth inhibition is incompletely understood. Studying head and neck cancer cells treated with human lactoferrin, we observed growth arrest in three of four cell lines tested. This growth arrest was caused by cell cycle inhibition at the G0-G1 checkpoint. Lactoferrin-induced growth inhibition was associated with a large increase in p27 protein, accompanied by decreased phosphorylation of retinoblastoma protein, and suppression of cyclin E. Decreased levels of phosphorylated Akt were also observed in lactoferrin-sensitive cell lines after treatment. These findings suggest that in head and neck cancer cells the growth inhibitory effects of lactoferrin are mediated through a p27/cyclin E-dependent pathway that may be modulated in part by changes in Akt phosphorylation.

Regulation of hematopoietic stem cell growth

Hematopoietic stem cells (HSC) must balance self-renewal and differentiation to provide sufficient primitive cells to sustain hematopoiesis, while generating more mature cells with specialized capabilities. The enhanced self-renewal capacity of primitive HSCs enables their ability to sustain hematopoiesis throughout decades of life and their ability to repopulate a host when used therapeutically in bone marrow transplantation. However, hematopoietic cell perturbations resulting in unchecked self-renewal participate in leukemogenesis. While mechanisms governing self-renewal are still being uncovered, they are thought to bear relationship to the malignant process in a variety of tumor types and may therefore provide useful therapeutic targets in putative cancer stem cells. This review discusses molecular mechanisms recently defined to participate in HSC governance and highlights features of stem cell interactions with the microenvironment that may help guide therapies directed at HSCs.

Essential function for ErbB3 in breast cancer proliferation

The overexpression of the ErbB family of tyrosine kinase receptors is thought to be important in the development of many breast tumours. To date, most attention has focused on the ErbB2 receptor. Now, in a recent report, it has been shown that ErbB3 is a critical partner for the transforming activity of ErbB2 in breast cancer cells. Importantly, the proliferative signals from this transforming complex appear to act via the PI-3 kinase pathway.

Foxm1b transcription factor is essential for development of hepatocellular carcinomas and is negatively regulated by the p19ARF tumor suppressor

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths worldwide. Here, we provide evidence that the Forkhead Box (Fox) m1b (Foxm1b or Foxm1) transcription factor is essential for the development of HCC. Conditionally deleted Foxm1b mouse hepatocytes fail to proliferate and are highly resistant to developing HCC in response to a Diethylnitrosamine (DEN)/Phenobarbital (PB) liver tumor-induction protocol. The mechanism of resistance to HCC development is associated with nuclear accumulation of the cell cycle inhibitor p27(Kip1) protein and reduced expression of the Cdk1-activator Cdc25B phosphatase. We showed that the Foxm1b transcription factor is a novel inhibitory target of the p19(ARF) tumor suppressor. Furthermore, we demonstrated that conditional overexpression of Foxm1b protein in osteosarcoma U2OS cells greatly enhances anchorage-independent growth of cell colonies on soft agar. A p19(ARF) 26-44 peptide containing nine D-Arg to enhance cellular uptake of the peptide was sufficient to significantly reduce both Foxm1b transcriptional activity and Foxm1b-induced growth of U2OS cell colonies on soft agar. These results suggest that this (D-Arg)(9)-p19(ARF) 26-44 peptide is a potential therapeutic inhibitor of Foxm1b function during cellular transformation. Our studies demonstrate that the Foxm1b transcription factor is required for proliferative expansion during tumor progression and constitutes a potential new target for therapy of human HCC tumors.

The V109G Polymorphism of the p27 Gene CDKN1B Indicates a Worse Outcome in Node-Negative Breast Cancer Patients

Although p27 plays a central role in cell cycle regulation, its role in breast cancer prognosis is controversial. Furthermore, the p27 gene CDKN1B carries a polymorphism with unknown functional relevance. This study was designed to evaluate p27 expression and p27 genotyping with respect to early breast cancer prognosis. 279 patients with infiltrating metastasis-free breast cancer were included in this study. p27 expression was determined in tumor tissue specimens from 261 patients by immunohistochemistry. From 108 patients, the CDKN1B genotype was examined by PCR and subsequent direct sequencing. 55.2% of the tumors were considered p27 positive. p27 expression did not correlate with any of the established parameters except for nodal involvement but significantly correlated to prolonged disease-free survival. In 35% of the tumors analyzed, the CDKN1B gene showed a polymorphism at codon 109 (V109G). The V109G polymorphism correlated with greater nodal involvement. In the node-negative subgroup, V109G correlated significantly with a shortened disease-free survival. In conclusion, the determination of the CDKN1B genotype might be a powerful tool for the prognosis of patients with early breast cancer.