A prospective multicentre phase III validation study of AZGP1 as a biomarker in localized prostate cancer

Background

Prostate cancers (PCs) with similar characteristics at the time of diagnosis can have very different disease outcomes. Conventional biomarkers of PC still lack precision in identifying individuals at high risk of PC recurrence. While many candidate biomarkers are proposed in the literature, few are in clinical practice as they lack rigorous validation. This study prospectively enrolled an independent phase III cohort to evaluate the clinical utility of zinc-alpha 2-glycoprotein (AZGP1) as a prognostic biomarker in localized PC.

Patients and methods

In our multicentre, prospective phase III study, AZGP1 status in 347 radical prostatectomy specimens was assayed by immunohistochemistry in a NATA-accredited laboratory. The AZGP1 score was assessed in a multivariable model incorporating established prognostic factors. We also report extended outcomes from our previous phase II study. The primary endpoint was biochemical relapse-free survival (BRFS). Secondary endpoints were metastasis-free survival (MFS) and PC-specific survival (PCSS).

Results

In the phase II cohort, with a median follow-up of 15.8 years, low/absent AZGP1 expression was an independent predictor of poor BRFS (HR, 1.4; 95% CI, 1.1-1.9; P = 0.03), MFS (HR, 2.8; 95% CI, 1.2-6.6; P = 0.02) and PCSS (HR, 3.8; 95% CI, 1.5-9.5; P = 0.005). These results were validated in our prospective phase III cohort. Low/absent AZGP1 expression independently predicted for BRFS (HR, 1.9; 95% CI, 1.1-3.3; P = 0.02), with shorter MFS (HR, 2.0; 95% CI, 1.1-3.4; P = 0.02). AZGP1 improved the discriminatory value when incorporated into existing prognostic risk models.

Conclusion

Our study provides prospective phase III validation that absent/low AZGP1 expression provides independent prognostic value in PC. This study provides robust evidence for the incorporation of this biomarker into clinical practice.

Cytokine profiling of docetaxel-resistant castration-resistant prostate cancer

Background:

Docetaxel improves symptoms and survival in metastatic castration-resistant prostate cancer (CRPC). However, ∼50% of patients are chemoresistant. This study examined whether changes in cytokine levels predict for docetaxel resistance in vitro and in a clinical cohort.

Methods:

PC3 cells or their docetaxel-resistant subline (PC3Rx) were co-cultured with U937 monocytes, with and without docetaxel treatment, and cytokine levels were measured. The circulating levels of 28 cytokines were measured pre-/post cycle 1 of docetaxel from 55 men with CRPC, and compared with prostate-specific antigen (PSA) response.

Results:

PC3Rx-U937 co-culture expressed more cytokines, chiefly markers of alternative macrophage differentiation, compared with PC3-U937 co-culture. Docetaxel treatment enhanced cytokine production by PC3Rx-U937 co-culture, while reducing cytokine levels in PC3-U937. In patients, changes in the levels of seven circulating cytokines (macrophage inhibitory cytokine 1 (MIC1), interleukin (IL)-1ra, IL-1β, IL-4, IL-6, IL-12 and IFNγ) after cycle 1 of docetaxel were associated with progressive disease (all P<0.05). The combination of changes in MIC1, IL-4 and IL-6 most strongly predicted PSA response (P=0.002).

Conclusions:

In vitro studies suggest docetaxel resistance is mediated, at least in part, by cytokines induced by the interaction between the docetaxel-resistant tumour cells and macrophages. Early changes in circulating cytokine levels were associated with docetaxel resistance in CRPC patients. When considered together, these data suggest a significant role for the inflammatory response and macrophages in the development of docetaxel resistance in CRPC.

The E3 ubiquitin ligase EDD is an adverse prognostic factor for serous epithelial ovarian cancer and modulates cisplatin resistance in vitro

Despite a high initial response rate to first-line platinum/paclitaxel chemotherapy, most women with epithelial ovarian cancer relapse with recurrent disease that becomes refractory to further cytotoxic treatment. We have previously shown that the E3 ubiquitin ligase, EDD, a regulator of DNA damage responses, is amplified and overexpressed in serous ovarian carcinoma. Given that DNA damage pathways are linked to platinum resistance, the aim of this study was to determine if EDD expression was associated with disease recurrence and platinum sensitivity in serous ovarian cancer. High nuclear EDD expression, as determined by immunohistochemistry in a cohort of 151 women with serous ovarian carcinoma, was associated with an approximately two-fold increased risk of disease recurrence and death in patients who initially responded to first-line chemotherapy, independently of disease stage and suboptimal debulking. Although EDD expression was not directly correlated with relative cisplatin sensitivity of ovarian cancer cell lines, sensitivity to cisplatin was partially restored in platinum-resistant A2780-cp70 ovarian cancer cells following siRNA-mediated knockdown of EDD expression. These results identify EDD as a new independent prognostic marker for outcome in serous ovarian cancer, and suggest that pathways involving EDD, including DNA damage responses, may represent new therapeutic targets for chemoresistant ovarian cancer.

Expression of LMO4 and outcome in pancreatic ductal adenocarcinoma

Identification of a biomarker of prognosis and response to therapy that can be assessed preoperatively would significantly improve overall outcomes for patients with pancreatic cancer. In this study, patients whose tumours exhibited high LMO4 expression had a significant survival advantage following operative resection, whereas the survival of those patients whose tumours had low or no LMO4 expression was not significantly different when resection was compared with operative biopsy alone.

Use of the novel biomarker (HOXB2) to predict response to pancreatectomy for pancreatic cancer

10526

Background: Pancreatectomy is the only therapeutic intervention that offers the chance of long term survival for patients with pancreatic cancer, however, only 10% of patients who undergo pancreatectomy survive > 3 years with prognostic factors only determined after pathological examination of the resected specimen. Identification of a biomarker of response to surgical resection that can be determined preoperatively offers the potential to significantly improve survival and quality of life for patients with PC by improving patient selection for pancreatectomy. Methods: We examined the aberrant expression of over 20 genes identified using transcript profiling or known to be important in carcinogenesis using immunohistochemistry and in-situ hybridisation in a cohort of 124 patients with pancreatic cancer to identify potential biomarkers of prognosis and response to operative resection. Results: Aberrant expression of p53, p21WAF1/CIP1, p27KIP1, p16INK4A, cyclin D1, cyclin E, DPC4/Smad4, EGFR, beta-catenin, sfrp4, LMO4, HOXB2, S100P, S100A6, S100A2, RAI3 and CRBP1 were identified in a significant proportion of PC. Multivariate analysis of clinicopathological variables (tumor size, differentiation, subtype, lymph node metastases, perineural invasion and vascular space invasion), treatment parameters (margin involvement, adjuvant therapy, resection type), and aberrant expression of the above candidate biomarkers identified that HOXB2 expression and resection margin involvement by tumor were the only 2 independent prognostic factors. Patients who had absent HOXB2 expression and had clear margins after pancreaticoduodenectomy (48%) had an actual survival of 40% at 3 years and 21% at 5 years, compared to those with HOXB2 expression and/or positive surgical margins who had all died by 28 months. Conclusion: HOXB2 expression may represent a surrogate marker of advanced disease, can potentially be assessed preoperatively using FNAB, and is currently the best predictor of outcome and response to operative resection to be reported. Preoperative assessment of HOXB2 expression has potential clinical utility in predicting response to operative resection for PC to allow better selection of patients for operative intervention.

No significant financial relationships to disclose.

Elevated multidrug resistance-associated protein 4 (MRP4) expression in localized prostate cancer—A potential androgen regulated protein

20022

Background: MRP4 is an ATP-binding cassette transporter and amphipathic anion efflux pump which transports prostaglandins, nucleoside analogues, glutamate and phosphate analogues. High MRP4 expression is prognostic of poor outcome in neuroblastoma and also correlates with MYCN amplification, suggesting regulation by this oncogene. Although MRP4 is known to be expressed in normal prostate epithelium, its expression in prostate cancer (PC) is undefined. This study aimed to define the pattern of expression of MRP4 in normal and malignant prostate tissue and assess the association with androgen exposure. Methods: 84 radical prostatectomy specimens from patients with clinically localized PC (22 neoadjuvant androgen ablation therapy, 62 no neoadjuvant treatment), 42 specimens of hyperplasia adjacent to PC and 16 cases of advanced PC were assessed for MRP4 expression using in situ hybridisation and immunohistochemistry. PC cell lines were assessed by immunoblotting. Results: There were significantly higher levels of MRP4 mRNA and protein expression in localized PC compared to hyperplasia (p=0.006). Conversely, MRP4 protein levels were significantly decreased in PCs treated with neoadjuvant androgen ablation therapy compared to cancers exposed to normal testosterone levels (p < 0.0001). There was also a trend towards decreased MRP4 expression in advanced PCs. Furthermore, immunoblotting revealed that MRP4 protein was more highly expressed in androgen-dependent (LNCaP) compared to androgen-independent (PC3/DU145) cell lines. In addition, in a panel of 14 normal human tissues only kidney and prostate tissue expressed MRP4 protein suggesting limited expression of MRP4 in human tissues. Discussion: Elevated MRP4 expression is found in malignant compared to benign prostate tissue while lower MRP4 expression is seen after androgen ablation suggesting that MRP4 may be an androgen-regulated gene. In addition, there is relatively little expression of MRP4 in normal tissues. These data suggest that MRP4 is important in the progression to PC and that it may be a potential therapeutic target.

No significant financial relationships to disclose.

A distinct molecular profile associated with mucinous epithelial ovarian cancer

Mucinous epithelial ovarian cancers (MOC) are clinically and morphologically distinct from the other histological subtypes of ovarian cancer. To determine the genetic basis of MOC and to identify potential tumour markers, gene expression profiling of 49 primary ovarian cancers of different histological subtypes was performed using a customised oligonucleotide microarray containing >59 000 probesets. The results show that MOC express a genetic profile that both differs and overlaps with other subtypes of epithelial ovarian cancer. Concordant with its histological phenotype, MOC express genes characteristic of mucinous carcinomas of varying epithelial origin, including intestinal carcinomas. Differences in gene expression between MOC and other histological subtypes of ovarian cancer were confirmed by RT–PCR and/or immunohistochemistry. In particular, galectin 4 (LGALS4) was highly and specifically expressed in MOC, but expressed at lower levels in benign mucinous cysts and borderline (atypical proliferative) tumours, supporting a malignant progression model of MOC. Hence LGALS4 may have application as an early and differential diagnostic marker of MOC.

Aberrant p16(INK4A) and DPC4/Smad4 expression in intraductal papillary mucinous tumours of the pancreas is associated with invasive ductal adenocarcinoma

BACKGROUND AND AIMS

Intraductal papillary mucinous tumours (IPMT) of the pancreas constitute a unique pathological entity with an overall incidence of associated invasive malignancy of 20%. The malignant potential of an individual IPMT cannot be accurately predicted. Preoperative estimation of the risk of associated invasive malignancy with IPMT would be of significant clinical benefit. As aberrations in cell cycle regulatory genes are associated with the progression of precursor pancreatic ductal lesions to invasive adenocarcinoma, we examined expression of key cell cycle regulatory genes in the cyclin D1/retinoblastoma pathway and the transforming growth factor beta/Smad4 signalling pathway in a cohort of patients with surgically resected IPMT.

METHODS

Sections of formalin fixed paraffin embedded pancreatic tissue from a cohort of 18 patients with IPMT were examined using immunohistochemistry for protein expression of cell cycle regulatory genes p16(INK4A), p21(CIP1), p27(KIP1), cyclin D1, pRb, and p53, as well as the cell signalling molecule Smad4. A comparison of expression levels was made between adenoma/borderline IPMT (10 patients) and intraductal papillary mucinous carcinoma (IPMC) (eight patients, four of whom harboured invasive carcinoma). Statistical analysis was performed using the chi(2) and Fisher's exact tests.

RESULTS

Aberrant expression of the proteins examined increased in frequency from adenoma/borderline IPMT to IPMC. Specifically, there was a significantly greater incidence of loss of p16(INK4A) expression in IPMC: 8/8 lesions (100%) compared with 1/10 (10%) adenoma/borderline IPMT (p<0.001). Similarly, loss of Smad4 expression was associated with IPMC: 3/8 (38%) versus adenoma/borderline IPMT 0/10 (p<0.03). Loss of Smad4 expression within the IPMT was the best marker for the presence of invasive carcinoma (p<0.001).

CONCLUSIONS

These data indicate that loss of p16(INK4A) and Smad4 expression occur more frequently in IPMC alone, or with associated invasive carcinoma, compared with adenoma/borderline IPMT. Aberrant protein expression of these cell cycle regulatory genes in IPMT and pancreatic intraepithelial neoplasia in the current model of pancreatic cancer progression suggest similarities in their development and may also represent the subsequent risk of invasive carcinoma.

Overexpression of p21(WAF1/CIP1) is an early event in the development of pancreatic intraepithelial neoplasia

Pancreatic cancer (PC) is thought to develop through a series of duct lesions termed pancreatic intraepithelial neoplasia (PanIN). Characterization of the molecular pathology of these lesions may lead to additional understanding of pancreatic ductal carcinogenesis. We examined the protein expression of four functionally related genes, p21(WAF1/CIP1) (CDKN1A), p53, cyclin D1 (CCND1), and DPC4/Smad4 (MADH4), aberrations of which are associated with PC, within 451 PanIN lesions present in the pancreata of 60 patients. p21(WAF1/CIP1) overexpression was present in the normal ducts of 9% of patients and increased progressively to 16% of patients with PanIN-1A lesions, to 32% of patients with PanIN-1B lesions, 56% of patients with PanIN-2 lesions, 80% of patients with PanIN-3 lesions, and 85% of patients with invasive carcinomas (P < 0.01). p53 and cyclin D1 overexpression occurred predominantly in PanIN-3 lesions (P < 0.01), and loss of DPC4/Smad4 expression occurred predominantly in PanIN-3 lesions and invasive carcinoma (P < 0.01). In addition, p21(WAF1/CIP1) overexpression occurred independently of p53 and DPC4/Smad4 expression within invasive carcinoma and PanIN-3 lesions. Cyclin D1 overexpression or loss of DPC4/Smad4 expression was apparent in 85% of invasive carcinomas but in only 14% of PanIN-2 lesions. These data demonstrate that overexpression of p21(WAF1/CIP1) occurs early in the development of PanIN, before aberrations in p53, cyclin D1, and DPC4/Smad4 expression. p21(WAF1/CIP1) overexpression, independent of p53 and/or DPC4/Smad4 expression, may reflect increased Ras activity, either directly through activating K-ras mutations or as a consequence of HER-2/neu (ERBB2) overexpression, both of which are common in PC and in early events in the development of PanIN. These data support further the current progression model for PC and demonstrate that aberrant expression of key cell cycle regulatory genes may be important in the early development and progression of PanIN.

Prognostic significance of pathologic features in localized prostate cancer treated with radical prostatectomy: implications for staging systems and predictive models

PURPOSE

Although predicting outcome for men with clinically localized prostate cancer (PC) has improved, the staging system and nomograms used to do this are based on results from the North American health system. To be internationally applicable, these models require testing in cohorts from a variety of different health systems based on the predominant PC case identification methods used.

PATIENTS AND METHODS

We studied 732 men with localized PC treated with radical prostatectomy and no preoperative therapy between 1986 and 1999 at one Australian institution to determine the effect of clinicopathologic features on disease-free survival.

RESULTS

Preoperative serum prostate-specific antigen (PSA) concentration, Gleason score, pathologic stage, and year of surgery were independent predictors of outcome. Although margin status demonstrated only a trend toward significance in multivariate modeling overall, it proved to be independent in subgroups based on later year of surgery (1986 to 1994 v 1995 to 1998), preoperative PSA of less than 10 ng/mL, and Gleason score > or = 7. Adjuvant radiation therapy improved disease-free survival rates in patients with multiple surgical margin involvement.

CONCLUSION

This work confirms the prognostic significance of pathologic stage, Gleason score, and preoperative serum PSA. In the context of a contemporaneous screening effect in Australia, these findings may have implications for methods that predict outcome following surgery as screening becomes more prevalent in a population. The independent prognostic effect of margin status may alter with an increase in the proportion of screening-identified PCs. Staging systems and nomograms that predict outcome following surgery require validation in cohorts with different health practices before being universally applied.

Frequent loss of estrogen receptor-beta expression in prostate cancer

The role of estrogen and its receptors in the etiology and progression of prostate cancer (PC) is poorly understood. In normal and malignant human prostate, estrogen receptor-alpha is expressed only in the stroma, whereas estrogen receptor-beta (ERbeta) is present in both normal stroma and epithelium. Because loss of ERbeta expression is associated with prostate hyperplasia in ERbeta-null mice, this study determined patterns of ERbeta expression in normal, hyperplastic, and malignant human prostate and associations with clinical outcome. Five normal prostates from organ donors and 159 radical prostatectomy specimens from patients with clinically localized PC were assessed for ERbeta expression using immunohistochemistry. ERbeta-positivity was defined as > or =5% of cells demonstrating nuclear immunoreactivity. All of the five normal prostates showed strong ERbeta-nuclear staining in >95% of the epithelium and 35% of the stromal cells. The number of ERbeta-positive cases declined to 24.2% (38/157) in hyperplasia adjacent to carcinoma and 11.3% (18/159) in PCs. ERbeta-positivity was related to decreased relapse-free survival (log-rank P = 0.04). Thus, loss of ERbeta expression is associated with progression from normal prostate epithelium to PC, whereas those cancers that retained ERbeta expression were associated with a higher rate of recurrence. These data identify the need to further investigate the potential role of ERbeta in the regulation of prostate epithelial cell proliferation and the functional consequences of decreased ERbeta expression in the evolution of PC.

Overexpression of the cell cycle inhibitor p16INK4A in high-grade prostatic intraepithelial neoplasia predicts early relapse in prostate cancer patients

Prostate cancer (PC) is the most commonly diagnosed male cancer in industrialized societies. No molecular markers of PC progression or outcome with proven clinical utility have been described. Because the loss of normal cell cycle control is an early event in the evolution of cancer, we sought to determine whether changes in expression of the cyclin-dependent kinase inhibitor, p16INK4A, predicted outcome in this disease. We screened a cohort of 206 patients with clinically localized PC treated with radical prostatectomy for overexpression of the INK4A gene, the product of which inactivates the G1-phase cyclin dependent kinases, Cdk4 and Cdk6. p16INK4A protein expression was evaluated by immunohistochemistry in areas of high-grade intraepithelial neoplasia (HGPIN), a precursor to invasive disease, and of cancer in the same specimen. Data were evaluated for disease relapse using the Kaplan-Meier method and in a Cox proportional hazards model by assessing p16INK4A status in areas of HGPIN and cancer with other variables of known clinical relevance. Overexpression of p16INK4A in HGPIN and cancer was correlated with, but independent of, pathological stage and was associated with early relapse in PC patients treated with radical prostatectomy (log-rank test, P < 0.001). In a multivariate model adjusted for Gleason grade, pretreatment prostate-specific antigen levels, pathological stage, and margin status, overexpression of p16INK4A in HGPIN was an independent predictor of disease relapse and increased the risk of recurrence 2.24-fold (95% confidence interval, 1.28-3.93). These data provide the first evidence for a prognostic marker in HGPIN. The clinical utility of p16INK4A status in stratifying patients for aggressive treatment very early in the disease process, potentially several years prior to the onset of invasive disease, requires further investigation.

Altered expression of androgen receptor in the malignant epithelium and adjacent stroma is associated with early relapse in prostate cancer

The molecular basis of androgen-independent prostate cancer is unknown; however, functional androgen receptor (AR) signaling is maintained after the acquisition of hormone-refractory disease. Because normal and malignant prostate epithelial cell proliferation is regulated by androgen stimulation via both the AR-positive stroma and epithelium, we sought to evaluate patterns of AR expression in these cells and to determine any relationships with prostate cancer progression. AR expression in the malignant epithelium and associated periepithelial and nonperiepithelial stroma was measured in a cohort of 96 patients with clinically localized prostate cancer treated with radical prostatectomy. Data were evaluated for disease relapse using the Kaplan-Meier method and in a Cox proportional hazards model with other variables of known clinical relevance, including Gleason score, pathological stage, clinical stage, and pretreatment prostate-specific antigen concentration. Concurrent overexpression of AR (> or = 70% positive nuclei) in the malignant epithelium and loss of AR immunoreactivity in the adjacent periepithelial stroma (< or = 30%) was associated with higher clinical stage (P = 0.01), higher pretreatment prostate-specific antigen level (P = 0.03), and earlier relapse after radical prostatectomy (log-rank P = 0.009). These data identify a pattern of AR expression in malignant epithelium and adjacent stroma that is associated with a poor clinical outcome in prostate cancer. Equally important, they identify the need to further investigate the mechanistic basis of loss of AR expression in the malignant stroma and its potential role in deregulation of prostate epithelial cell proliferation.

Prognostic significance of p53 nuclear accumulation in localized prostate cancer treated with radical prostatectomy

The role of p53 in the pathogenesis of, and as a predictive biomarker for, localized prostate cancer (PCa) is contested. Recent work has suggested that patterns of p53 nuclear accumulation determined by immunohistochemistry are prognostic, whereas studies using other methods question the role of p53 mutations in predicting outcome. We studied 263 men with localized PCa treated with radical prostatectomy to determine whether p53 nuclear accumulation predicts relapse and disease-specific mortality. We combined two p53 immunohistochemistry scoring systems: (a) percentage of p53-positive tumor nuclei in all major foci of cancer within the prostate; and (b) clustering, where the presence of 12 or more p53-positive cells within a x 200 power field was deemed "cluster positive." Analysis was undertaken using chi2, Kruskal-Wallis, and Mann-Whitney tests for clinicopathological variables and the Kaplan-Meier method, log-rank test, and univariate and multivariate Cox regression modeling for evaluation of contribution to relapse and disease-specific survival. At mean follow-up of 55.1 months (range, 4.9-123.0 months), 39% (102 of 263) of patients had relapsed and 2.3% (6 of 253) had died of PCa. Pretreatment serum prostate-specific antigen concentration, pathological tumor stage, lymph node involvement, Gleason score, and p53 nuclear accumulation, as determined by either percentage score or cluster status, were independent predictors of relapse in multivariate analysis. Clustering of p53-positive cells distinguished between favorable and poor prognosis patients within the lowest p53-positive stratum (>0 to <2%) and was the most discriminatory threshold for predicting relapse in the entire cohort. p53 status predicted outcome in patients with a Gleason score of 5 and above but not those with a score of 4 and below. In patients treated with neoadjuvant hormonal therapy, p53 cluster positivity carried a 90% (19 of 21) risk of relapse by 36 months. All six patients who died from PCa in the period of the study exhibited p53 nuclear accumulation in 20% or more tumor nuclei. This study demonstrates strong relationships between p53 nuclear accumulation and relapse and disease-specific mortality in a large series of localized PCas. Furthermore, the presence of clusters of p53-positive nuclei delineates a group of patients with poor prognosis not identified by traditional scoring methods and supports the hypothesis that p53 dysfunction within PCa may exist in foci of tumor cells that are clonally expanded in metastases.

Cyclin D1 protein is overexpressed in hyperplasia and intraductal carcinoma of the breast

The cell cycle regulatory gene cyclin D1 is a candidate oncogene in breast cancer. It is overexpressed in 30-50% of invasive primary breast cancers and plays a key role in mediating mitogenic responses to steroids and growth factors in breast cancer cells in vitro. Because the role of cyclin D1 in the proliferative and early noninvasive stages of breast cancer is largely unknown, we examined normal breast epithelium (NBE), proliferative disease (PD), ductal carcinoma in situ (DCIS), and invasive carcinoma (IC) to evaluate the timing and possible importance of cyclin D1 expression in the development of breast cancer. Using immunohistochemistry, we examined cyclin D1 protein expression in 471 breast tissue samples. A quantitative scoring system for immunohistochemistry based on percentage of positive cells was developed that correlated with Western blot analysis of antigen concentration in paired samples (r2 = 0.91, P = 0.003). A sample was considered positive if >5% of relevant epithelial cells demonstrated nuclear staining. Cyclin D1 positivity was observed in 11.7% (7 of 60) samples of NBE, 25% (11 of 44) of PD without atypia, 39.4% (13 of 33) of atypical ductal hyperplasia, 43.6% (17 of 39) of low-grade DCIS, 47.9% (23 of 48) of high-grade DCIS, and 48.3% (99 of 205) of IC. Cyclin D1 expression was significantly higher in PD than NBE (P = 0.006) and in DCIS than PD (P = 0.038). There was no significant increase from DCIS to IC (P = 0.52). The increase in cyclin D1 expression in the overall progression from NBE to IC was also highly significant (P = 0.0001). Therefore, cyclin D1 expression was detected at levels significantly greater than in NBE in the earliest proliferative epithelial lesions of the breast with a further significant increase accompanying the progression to any form of cancer. This suggests that overexpression of cyclin D1 protein is important at the earliest stages of breast oncogenesis and continues to have a crucial role throughout the development of malignancy.