Decreasing of p27(Kip1)and cyclin E protein levels is associated with progression from superficial into invasive bladder cancer

The p27(Kip1)(p27) protein is a cyclin-dependent kinase inhibitor of the transition from G1 to S phase. It has been reported that decreased p27 protein level is a negative prognostic indicator in human tumours including bladder cancer. We studied the relationship between protein levels of p27, cyclin E and Ki-67 and clinicopathological features of 145 consecutive Japanese patients with transitional cell carcinoma of the bladder using immunohistochemical staining. Low protein levels of p27 were associated with low staining of cyclin E (P = 0.0302), high Ki-67 index (P = 0.0306), poorly differentiated grade (P = 0.0006), muscle invasion (P = 0.0019) and lymph node metastsis (P = 0.0002). Low staining of cyclin E and high Ki-67 index correlated with poorly differentiated grade, muscle invasion and lymph node metastsis. Cyclin E protein levels was inversely related with Ki-67 index (P = 0.0002). Kaplan-Meier plots of survival rate in patients with low versus high p27 staining showed that low protein levels of p27 were associated with a shortened disease-free and overall survival (P< 0.0001 and P< 0.0001, respectively). Similarly, low staining of cyclin E and high Ki-67 index correlated with a shortened disease-free and overall survival. On multivariate analysis using Cox proportional hazards model, low protein levels of p27 and high Ki-67 index were independent predictors of shortened disease-free (P< 0.0001, P = 0.0031, respectively), and low protein levels of p27, low staining of cyclin E and high Ki-67 index of overall survival (P = 0.0017, P = 0.0009, P = 0.0003, respectively). In superficial bladder tumours (Ta, T1; 86 patients), significant correlations were observed between low p27 staining and high Ki-67 index and early recurrence (P = 0.0048, P = 0.0178, respectively). Among the recurrenced superficial tumours (35 patients), the tumours which remained at a low stage showed high protein levels of p27 and cyclin E, and the tumours which progressed to invasive disease showed a gradual decrease in p27 and cyclin E protein levels over time. Our findings suggest that decreased protein levels of p27 and cyclin E play a role in the progression of bladder cancer and to evaluate these protein levels may be useful in management of the diseases.     

Adhesion control of cyclin D1 and p27Kip1 levels is deregulated in melanoma cells through BRAF-MEK-ERK signaling

Mutations in BRAF, a component of extracellular signal-regulated kinases 1 and 2 (ERK) cascade, are frequent in melanoma. It is important to understand how BRAF mutations contribute to malignant traits including anchorage- and growth factor-independence. We have previously shown that efficient activation of ERK in normal human epidermal melanocytes (NHEM) requires both adhesion to the extracellular matrix and growth factors. Mutant V599E BRAF is sufficient to promote ERK activation independent of adhesion and growth factors. Here, we analysed regulation of G1 cell cycle events in NHEM and human melanoma cells. We show that S phase entry in NHEM requires both adhesion and growth factor signaling through the MEK-ERK pathway. This control correlates with induction of cyclin D1 and downregulation of p27Kip1, two key G1 cell cycle events. In melanoma cells expressing V599E BRAF, cyclin D1 was constitutively expressed independent of adhesion but dependent upon MEK activation and nuclear accumulation of ERK. Reduction of cyclin D1 levels by RNA interference inhibited S phase entry in melanoma cells. Importantly, expression of V599E BRAF in NHEM was sufficient to promote cyclin D1 promoter activity in the absence of adhesion. Additionally, p27Kip1 levels were downregulated in V599E BRAF-expressing melanoma cells and active BRAF was sufficient to downregulate p27Kip1 in serum-starved NHEM. Thus, adhesion-growth factor cooperation, leading to efficient activation of ERK, regulates cyclin D1 and p27Kip1 levels in human melanocytes and mutant BRAF overrides adhesion-growth factor control of these two G1 cell cycle proteins in melanomas. These findings provide important insight into how BRAF mutations contribute to aberrant human melanocyte proliferation.     

Retinoic acid-mediated growth inhibition of small cell lung cancer cells is associated with reduced myc and increased p27Kip1 expression

Human lung cancer cells, including small cell lung carcinoma (SCLC), frequently lose expression of retinoic acid receptor beta (RAR-beta) and are resistant to the growth inhibitory activity of all-trans retinoic acid (RA). To elucidate the role of RAR-beta in the growth regulation of SCLC by retinoids, we restored RAR-beta expression in RAR-beta-negative H209 SCLC cells by retroviral transduction (H209-RAR-beta). We found that H209-RAR-beta, but not parental H209 cells, underwent growth inhibition upon RA treatment. RA-treated H209-RAR-beta cells arrested in G1 and displayed reduced L-myc expression and cyclin-dependent kinase 2 (cdk2) activity compared with untreated cells. RA treatment of H209-RAR-beta cells was also accompanied by increased expression of the cdk inhibitor p27Kip1, whereas no differences in the expression of L-myc or p27Kip1 were detected upon RA treatment of parental H209 cells. The RA-induced growth arrest of H82 SCLC cells, which express endogenous RAR-beta, was also associated with reduced c-myc and increased p27Kip1 expression. We found that ectopic expression of p27Kip1 induced growth inhibition in both H209 and H82 cells, and that sustained myc expression in H209-RAR-beta cells promoted the induction of apoptosis upon RA addition. Our observations indicate that RAR-beta gene transfer can restore RA sensitivity in SCLC cells and suggest that myc and p27Kip1 may represent critical mediators of the RA-induced cell cycle arrest in SCLC cells expressing RAR-beta.     

Cyclin D1 is necessary for tamoxifen-induced cell cycle progression in human breast cancer cells

Despite the success of tamoxifen in treating hormone-responsive breast cancer, its use is limited by the development of resistance to the drug. Understanding the pathways involved in the growth of tamoxifen-resistant cells may lead to new ways to treat tamoxifen-resistant breast cancer. Here, we investigate the role of cyclin D1, a mediator of estrogen-dependent proliferation, in growth of tamoxifen-resistant cells using a cell culture model of acquired resistance to tamoxifen. We show that tamoxifen and 4-hydroxytamoxifen (OHT) promoted cell cycle progression of tamoxifen-resistant cells after growth-arrest mediated by the estrogen receptor down-regulator ICI 182,780. Down-regulation of cyclin D1 with small interfering RNA blocked basal cell growth of tamoxifen-resistant cells and induction of cell proliferation by OHT. In addition, pharmacologic inhibition of phosphatidylinositol 3-kinase/Akt or mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 pathways decreased basal cyclin D1 expression and impaired OHT-mediated cyclin D1 induction and cell cycle progression. These findings indicate that cyclin D1 expression is necessary for proliferation of tamoxifen-resistant cells and for tamoxifen-induced cell cycle progression. These results suggest that therapeutic strategies to block cyclin D1 expression or function may inhibit development and growth of tamoxifen-resistant tumors.     

Expression of p27Kip1 and cyclin D1 proteins is inversely correlated and is associated with poor clinical outcome in human gastric cancer.

BACKGROUND AND OBJECTIVES: p27Kip1 is an inhibitor of cyclin-dependent kinases and is speculated to be a potential prognostic indicator in numerous human cancers. We investigated expression of p27Kip1 along with cyclin D1 in gastric cancer to estimate the clinical utility of p27Kip1. METHODS: Immunohistochemical assay for p27Kip1 and cyclin D1 proteins was performed in 64 patients with primary gastric cancer. Correlation between p27Kip1 expression and clinical-biological parameters including patient survival was analyzed. RESULTS: p27Kip1 expression was suppressed in 40 (62.5%) of 64 gastric cancer patients and cyclin D1 was overexpressed in 22 (34.4%) out of 64. Expression of p27Kip1 was significantly reduced in poorly differentiated cancers (82.1%, 23/28; P = 0.015) and was also reduced in the tumors with high S-phase fraction (86.7%, 26/30) compared with tumors showing low S-phase fraction (41.2%, 14/34; P = 0.0002). Expression of p27Kip1 and cyclin D1 was inversely correlated (P = 0.021). In univariate analysis, extent of the disease (P < 0.001), expression of cyclin D1 (P = 0.0001), and reduced expression of p27Kip1 (P = 0. 0006), were statistically significant to predict patient's outcome, but depth of invasion (P = 0.008) and pathologic stage (P = 0.009) emerged as significant prognostic indicators in multivariate analysis. CONCLUSION: Expression of p27Kip1 is closely linked with cell proliferation and differentiation of human gastric cancer. p27Kip1 seems to have potential as a prognostic marker in the management of gastric cancer patients.     

Antiestrogen regulation of cell cycle progression and cyclin D1 gene expression in MCF-7 human breast cancer cells

The molecular mechanisms by which antiestrogens inhibit breast cancer cell proliferation are not well understood. Using cultured breast cancer cell lines, we studied the effects of antiestrogens on proliferation and cell cycle progression and used this information to select candidate cell cycle regulatory genes that are potential targets for antiestrogens. Under estrogen- and serum-free conditions antiestrogens inhibited proliferation of MCF-7 cells stimulated with insulin. Cells were blocked at a point in G₁ phase. These effects are comparable with those in serum- and estrogen-containing medium and were also seen to a lesser degree in nude mice bearing MCF-7 tumors. Similar observations with other peptide mitogens suggest that the process inhibited by antiestrogens is common to estrogen and growth factor activated pathways. Other studies have identified G₁ cyclins as potential targets for growth factor and steroid hormone/steroid antagonist regulation of breast epithelial cell proliferation. In MCF-7 cells growing in the presence of fetal calf serum, cyclin D1 mRNA was rapidly down-regulated by steroidal and nonsteroidal antiestrogens by an apparently estrogen receptor mediated mechanism. Cyclin D1 gene expression was maximally inhibited before effects on entry into S phase and inhibition was therefore not merely a consequence of changes in cell cycle progression. Together with data on the effects of antiestrogens in serum-free conditions [1], these results suggest down-regulation of cyclin D1 by antiestrogens may be a general phenomenon in estrogen receptor-positive breast cancer cells, independent of culture conditions and class of antiestrogen. These observations are compatible with the hypothesis that reductions in cyclin D1 levels may mediate in part the action of antiestrogens in blocking entry of cells into S phase.     

KIS induces proliferation and the cell cycle progression through the phosphorylation of p27Kip1 in leukemia cells

CEM, MOLT4 and SUP-B15 cells were transduced with lentivirus-mediated siRNA KIS gene. The mRNA expressions of KIS were successfully reduced in all cell lines. On the other hand, the mRNA expressions of p27(Kip1) in CEM, MOLT4 and SUP-B15 cells were not affected by the transduction with siRNA KIS gene. We showed that KIS protein directly interacted with p27(Kip1) protein, and reduction of KIS inhibited the S10 phosphorylation of p27(Kip1) in leukemia cells. On these cells transfected with siRNA KIS, the inhibition of S10 phosphorylation of p27(Kip1) was strongly suppressed cell proliferation in a time-dependent manner. Moreover, the inhibition of S10 phosphorylation of p27(Kip1) increased a significant population in G0/G1 fraction. These data demonstrated that the KIS activity was induced during G0/G1, and it promotes cell cycle progression by phosphorylation of S10 on p27(Kip1). We showed that KIS mRNA expression was increased in primary leukemia specimens (acute myelogenous leukemia (AML); 37, myelodysplastic syndrome (MDS); 72, acute lymphoblastic leukemia (ALL); 23), and the mean ratios of KIS to G3PDH in AML, MDS and ALL specimens were 3.62+/-0.68, 3.27+/-0.73 and 3.17+/-0.58, respectively. Moreover, we found that KIS protein was overexpressed in all 132 adults cases of various leukemias, including 37 AML (8 M1, 12 M2, 2 M3, 7 M4, 8 M5), 72 MDS (42 RAEB-I, 30 REAB-II) and 23 ALL (23 L2). This study demonstrates that the elevated levels of KIS protein in leukemia cells promote the cell cycle progression in leukemia cells.     

Jun activation domain binding protein 1 expression is associated with low p27(Kip1)levels in node-negative breast cancer.

PURPOSE: The purpose is to evaluate expression levels of Jun activation domain-binding protein 1 (JAB1) in breast cancer tissue and adjacent normal tissue, to determine whether JAB1 expression is associated with p27(Kip1) expression in invasive breast carcinomas, and to evaluate the prognostic significance of JAB1 and p27(Kip1) in node-negative breast cancer. EXPERIMENTAL DESIGN: JAB1 levels were measured in 10 matched pairs of invasive breast tumor tissue and adjacent normal tissue using Western blot analysis. We also investigated the immunoreactivity of JAB1 and p27(Kip1) levels in paraffin-embedded tissue specimens from 220 patients with node-negative breast cancer who had not received adjuvant systemic therapy. The median follow-up was 15 years. RESULTS: JAB1 was expressed at higher levels in invasive tumors than in adjacent normal tissue (P = 0.01). JAB1 overexpression was observed in 57% of invasive breast cancers. Low levels of p27(Kip1) were noted in 70% of the tumor specimens. We found an inverse correlation between JAB1 and p27(Kip1) expression levels (P = 0.01). JAB1 overexpression was associated with patient age of at least 50 years (P = 0.03) and tumor size of 相似文献   

Functional analysis of cyclin D2 and p27(Kip1) in cyclin D2 transgenic mouse mammary gland during development

Two mammary gland phenotypes were detected in pregnant MMTV-cyclin D2 transgenic mice; line D2-53 exhibited a lack of alveologenesis and failure to nurse, whereas line D2-58 featured a reduction in alveologenesis, but retained normal nursing behavior. In pregnant mammary glands, cyclin D2 protein levels were twofold (P<0.107) and 3.8-fold (P<0.0076) higher in line D2-58 and D2-53, respectively, compared to wild type. Concomitantly with the increase in cyclin D2 was a fivefold decrease in cyclin D1 hyper-phosphorylated isoform in mammary glands of pregnant cyclin D2-58 mice. Because cyclin D1 is a critical molecule in normal mammary lobuloalveolar development, these data suggest that overexpression of cyclin D2 may block mammary lobuloalveolar development through inhibition of cyclin D1 phosphorylation. During mammary gland development, p27(kip1) protein level oscillated in a similar profile in wild type and cyclin D2 transgenic mice, but was consistently higher in the cyclin D2 mice suggesting that p27(kip1) functions downstream of cyclin D2. The ratio of p27(kip1)-cdk4/p27(kip1)-cdk2 was 6.5-fold (P<0.0003) higher in cyclin D2 mammary glands compared to wild type in pregnant animals. This ratio reversed to 2.2-fold (P<0.005) higher in wild type compared to cyclin D2 mammary glands in involution suggesting that overexpression of cyclin D2 moderately induced apoptosis during pregnancy but accelerated involution. Collectively, the effects of cyclin D2 overexpression on mammary gland development during pregnancy and involution are attributed to two major factors, altered p27(kip1) protein level and inhibition of cyclin D1 phosphorylation.     

Cdk2 is dispensable for cell cycle inhibition and tumor suppression mediated by p27(Kip1) and p21(Cip1)

p27(Kip1) and p21(Cip1) are thought to suppress tumor growth and prevent cell cycle progression by inhibiting Cdk2-cyclin E/A kinases. Since Cdk2 is dispensable for mitotic cell division, we analyzed the activity of these inhibitors in Cdk2-deficient cells. Ectopic expression of p27(Kip1) or p21(Cip1) efficiently inhibits cell cycle progression of Cdk2(-/-) fibroblasts. Loss of p27(Kip1) or p21(Cip1) confers similar proliferative advantages to Cdk2(+/+) and Cdk2(-/-) cells. Moreover, Cdk2 is dispensable for p21(Cip1)-induced cell cycle arrest after DNA damage. Finally, ablation of Cdk2 in p27(Kip1) null mice does not suppress their phenotypic defects, including development of pituitary tumors. These results indicate that Cdk2 is not an essential target for p27(Kip1) and p21(Cip1) in cell cycle inhibition and tumor suppression.     

Prognostic implication of cyclin E expression and its relationship with cyclin D1 and p27Kip1 expression on tissue microarrays of node negative breast cancer

BACKGROUND AND OBJECTIVES: Altered expression of cell-cycle regulators is prevalent in clinical breast cancer. This study was performed to analyze the impact of cyclin E expression to the outcome of breast cancer together with cyclin D1 and p27Kip1. METHODS: The correlation between cyclin D1/E and p27Kip1 expression was analyzed in tissue arrays of 175 node-negative breast cancers treated by the same chemotherapy composed of fluorouracil, cyclophosphamide, and methotrexate. Data from the immunohistochemical assays of three molecules were correlated and were analyzed with clinical outcome of the patients. RESULTS: Cyclin E expression was observed in 48 (27.4%) of 175 breast carcinomas. Cyclin E expression was significantly increased in young age patients and poorly differentiate tumors. Expression of cyclin E was significantly increased in cyclin D1 expressing tumors (P = 0.034). p27Kip1 expression was preserved above the 50% level in 87 tumors (49.7%) and was inversely correlated with cyclin E expression (P = 0.042). Ki67 labeling index was significantly increased in cyclin E-expressing tumors (P = 0.033) and was inversely related with p27Kip1 expression. In multivariate survival analysis, cyclin E expression was significant for the prediction of poor survival of the patients. CONCLUSIONS: Cyclin E expression was associated with poor prognosis and intimately correlated with the expression of cyclin D1 and p27Kip1. Integration of TMA technology allowed a high-throughput analysis for correlating molecular in situ findings with clinico-pathologic information.     

PTEN induces G(1) cell cycle arrest and decreases cyclin D3 levels in endometrial carcinoma cells

Inactivating mutations in the PTEN tumor suppressor gene occur in approximately 30-50% of endometrial carcinomas. PTEN is a phosphatase that negatively regulates the phosphoinositide 3-kinase signaling pathway, including the downstream effector AKT. To evaluate the role of PTEN in endometrial growth regulation, we expressed wild-type or mutant PTEN in endometrial carcinoma cell lines. As expected, expression of exogenous PTEN decreased levels of activated AKT in all cell lines examined. However, PTEN induced a G(1) cell cycle arrest specifically in endometrial carcinoma cells that lack endogenous wild-type PTEN. Growth of cells containing wild-type PTEN was unaffected by exogenous PTEN expression. Growth arrest required a functional phosphatase domain but not the PDZ interaction motif of PTEN. Overall levels of CIP/KIP and INK4 family members, the known inhibitory regulators of the G(1) phase of the cell cycle, were unchanged. However, PTEN induced a specific reduction of cyclin D3 levels and an associated increase in the amount of the inhibitor p27(KIP1) complexed with CDK2. Enforced expression of cyclin D3 abrogated the PTEN-induced cell cycle arrest. Although PTEN signaling directly regulates p27(KIP1) levels in some settings, in endometrial carcinoma cells, PTEN expression indirectly regulated p27(KIP1) activity by modulating levels of cyclin D3. These data support multiple mechanisms of PTEN-induced cell cycle arrest.     

Caffeic acid phenethyl ester induced cell cycle arrest and growth inhibition in androgen-independent prostate cancer cells via regulation of Skp2, p53, p21Cip1 and p27Kip1

Prostate cancer (PCa) patients receiving the androgen ablation therapy ultimately develop recurrent castration-resistant prostate cancer (CRPC) within 1–3 years. Treatment with caffeic acid phenethyl ester (CAPE) suppressed cell survival and proliferation via induction of G1 or G2/M cell cycle arrest in LNCaP 104-R1, DU-145, 22Rv1, and C4–2 CRPC cells. CAPE treatment also inhibited soft agar colony formation and retarded nude mice xenograft growth of LNCaP 104-R1 cells. We identified that CAPE treatment significantly reduced protein abundance of Skp2, Cdk2, Cdk4, Cdk7, Rb, phospho-Rb S807/811, cyclin A, cyclin D1, cyclin H, E2F1, c-Myc, SGK, phospho-p70S6kinase T421/S424, phospho-mTOR Ser2481, phospho-GSK3α Ser21, but induced p21^Cip1, p27^Kip1, ATF4, cyclin E, p53, TRIB3, phospho-p53 (Ser6, Ser33, Ser46, Ser392), phospho-p38 MAPK Thr180/Tyr182, Chk1, Chk2, phospho-ATM S1981, phospho-ATR S428, and phospho-p90RSK Ser380. CAPE treatment decreased Skp2 and Akt1 protein expression in LNCaP 104-R1 tumors as compared to control group. Overexpression of Skp2, or siRNA knockdown of p21^Cip1, p27^Kip1, or p53 blocked suppressive effect of CAPE treatment. Co-treatment of CAPE with PI3K inhibitor {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 or Bcl-2 inhibitor ABT737 showed synergistic suppressive effects. Our finding suggested that CAPE treatment induced cell cycle arrest and growth inhibition in CRPC cells via regulation of Skp2, p53, p21^Cip1, and p27^Kip1.     

Jun activation domain-binding protein 1 expression in breast cancer inversely correlates with the cell cycle inhibitor p27(Kip1)

The Jun activation domain-binding protein 1 (JAB1), aside from being an activator protein 1 coactivator, is involved in degradation of the cyclin-dependent kinase inhibitor p27. We examined JAB1 and p27 protein expression in invasive breast carcinoma specimens and the association of this expression with clinical outcome. JAB1 was detected immunohistochemically in 43 of 53 (81%) tumors; 32 (60%) breast carcinomas showed high JAB1 expression (>50% of cells positive) and reduced or absent p27 levels (P = 0.02, Mann-Whitney U test). Tumors with high p27 expression were rarely positive for JAB1. All eight patients with JAB1-negative tumors had no evidence of relapse or disease progression at a median follow-up of 70 months. Immunoblotting showed strong JAB1 expression in breast carcinoma samples but not in paired normal breast epithelial samples. Targeted overexpression of JAB1 by regulated adenovirus in breast cancer cell lines also reduced p27 levels by accelerating degradation of p27. Thus, the JAB1:p27 ratio may be a novel indicator of aggressive, high-grade tumor behavior, and control of JAB1 could be a novel target for experimental therapies.     

Prognostic role of p27Kip1 and apoptosis in human breast cancer

Human breast carcinoma is biologically heterogeneous, and its clinical course may vary from an indolent slowly progressive one to a course associated with rapid progression and metastatic spread. It is important to establish prognostic factors which will define subgroups of patients with low vs high risk of recurrence so as to better define the need for additional therapy. Additional characterization of the molecular make-up of breast cancer phenotypes should provide important insights into the biology of breast cancer. In the present study, we investigated apoptosis, expression of p27Kip1 and p53 retrospectively in 181 human breast cancer specimens. In addition, their relevance to the biological behaviour of breast cancer was examined. Our studies found a significant association among high histological grade, high p53, low apoptosis and low p27. Our results also demonstrated that, in human breast cancer, low levels of p27 and apoptotic index (AI) strongly correlated with the presence of lymph node metastasis and decreased patient survival. In node-negative patients, however, p27 also had prognostic value for relapse-free and overall survival in multivariate analysis. Furthermore p27 and AI had predictive value for the benefits of chemotherapy. These latter observations should prompt prospective randomized studies designed to investigate the predictive role of p27 and AI in determining who should receive chemotherapy in node-negative patients.     

Expression of cell cycle associated proteins cyclin A, CDK-2, p27kip1 and p53 in equine sarcoids

Equine sarcoids are benign fibroblastic skin tumours affecting equids worldwide. Whilst the pathogenesis is not entirely understood, infection with Bovine Papillomavirus (BPV) types 1 and 2 has been implicated as a major factor in the disease process, however the mechanism by which BPV infection contributes to sarcoid pathology is not clear. In this study, we show that the majority of sarcoids express the BPV-1 major transforming gene E6. Further, we demonstrate that sarcoid lesions are not associated with high levels of cellular proliferation as assessed by Ki67 expression or with expression of cell cycle regulators CDK-2, cyclin A and p27kip1. Our analysis of p53 shows that a subset of sarcoids are associated with abnormal cytoplasmic and nuclear expression of p53 and that the transactivation function of p53 is compromised in cells with cytoplasmic p53.     

Inactivation of PTEN is associated with a low p27Kip1 protein expression in breast carcinoma

BACKGROUND: It was previously demonstrated that PTEN protein expression is reduced in 67 of 236 (28%) breast carcinomas. Recent experimental studies suggested that the cell cycle inhibitor p27Kip1 (p27) is a downstream mediator through which PTEN negatively regulates cell cycle progression. METHODS: The immunohistochemic expression of p27 and PTEN protein expression was evaluated in a series of 228 invasive ductal carcinomas of the breast. RESULTS: PTEN protein expression was found to have decreased in 65 of 228 (29%) cases, while the nuclear accumulation of p27 protein was low in 99 of 228 (43%) cases. A reduced PTEN protein expression correlated significantly (P = 0.0214) with a low p27 protein expression. Univariate analysis indicated that the patients demonstrating a combined decrease in PTEN and p27 protein expression have a significantly (P = 0.0044) worse disease-free survival (DFS) than those with other combinations of these two protein expression patterns, while multivariate analysis indicated that the lymph node status, MIB-1 counts, and the combination of PTEN/p27 protein expression (P = 0.0452) are independently significant prognostic factors for DFS. CONCLUSIONS: A reduced PTEN protein expression correlated significantly with a low p27 protein expression in breast carcinoma. The finding that the patients with a combined decrease in both protein expressions had a poor prognosis thus suggests that a combined loss of PTEN and p27 function is associated with an aggressive phenotype in breast carcinoma.