Retinoblastoma (RB1) gene product expression in breast carcinoma. Correlation with Ki-67 growth fraction and biopathological profile

Patients with Invasive Lobular Carcinoma Show a Significant Increase in IRS-4 Expression Compared to Infiltrative Ductal Carcinoma—A Histopathological Study

Background and Objectives: Breast cancer (BC) is the first diagnosed type of cancer and the second leading cause of cancer-related mortality in women. In addition, despite the improvement in treatment and survival in these patients, the global prevalence and incidence of this cancer are rising, and its mortality may be different according to the histological subtype. Invasive lobular carcinoma (ILC) is less common but entails a poorer prognosis than infiltrative ductal carcinoma (IDC), exhibiting a different clinical and histopathological profile. Deepening study on the molecular profile of both types of cancer may be of great aid to understand the carcinogenesis and progression of BC. In this sense, the aim of the present study was to explore the histological expression of Insulin receptor substrate 4 (IRS-4), cyclooxygenase 2 (COX-2), Cyclin D1 and retinoblastoma protein 1 (Rb1) in patients with ILC and IDC. Patients and Methods: Thus, breast tissue samples from 45 patients with ILC and from 45 subjects with IDC were analyzed in our study. Results: Interestingly, we observed that IRS-4, COX-2, Rb1 and Cyclin D1 were overexpressed in patients with ILC in comparison to IDC. Conclusions: These results may indicate a differential molecular profile between both types of tumors, which may explain the clinical differences among ILC and IDC. Further studies are warranted in order to shed light onto the molecular and translational implications of these components, also aiding to develop a possible targeted therapy to improve the clinical management of these patients.

Ki67 and progesterone receptor status predicts sensitivity to palbociclib: a real-world study

Background

Palbociclib combined with endocrine therapy has been approved as a front-line treatment for hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2-) advanced breast cancer (ABC). A key challenge remains to uncover biomarkers to identify those patients who may benefit from palbociclib treatment.

Methods

We retrospectively analyzed the values of Ki67 and progesterone receptor (PR) as detected by immunohistochemistry in 81 ABC patients with palbociclib and hormone therapy treatment, and evaluated the impact on progression-free survival (PFS).

Results

In the total population, women with Ki67 ≥14% had marginally significantly shorter PFS than those with Ki67 <14% (P=0.062). Patients with Ki67 ≥30% had significantly shorter PFS than those with Ki67 <30% (P=0.048). Meanwhile, PR ≥20% was associated with longer PFS. Moreover, the change of Ki67 or PR from primary tissue to metastatic lesions was related to PFS. As for the hormone therapy subgroup, there were significant associations between Ki67 and PR levels and PFS in the aromatase inhibitors (AIs) subgroup. Patients with Ki67 ≥14% or Ki67 ≥30% had shorter PFS than those with Ki67 <14% or Ki67 <30%, respectively (P=0.024, P<0.001). Additionally, the change of Ki67 or PR from primary tissue to metastatic lesions was related to PFS. When both Ki67 and PR were considered, there were significant differences between the different cohorts. Compared with patients with Ki67 ≥14% and PR <20%, those with Ki67 <14% and PR ≥20% had significantly longer PFS. In addition, patients with Ki67 <30% and PR ≥20% had significantly longer PFS than those with Ki67 ≥30% and PR <20%. Furthermore, in the AI cohort, patients with Ki67 <14% and PR ≥20% had significantly longer PFS than those with Ki67 ≥14% and PR <20%. Women with Ki67 <30% and PR ≥20% had significantly longer PFS than those with Ki67 ≥30% and PR <20%.

Conclusions

The present study indicates that both Ki67 and PR have great impacts on palbociclib and hormone therapy and may contribute to selecting more effective partners for palbociclib.

Ki67 and PR in Patients Treated with CDK4/6 Inhibitors: A Real-World Experience

CDK4/6 inhibitors (CDK4/6i) are recommended in patients with estrogen receptor (ER)-positive, HER2-negative advanced breast cancer (ABC). Up to now, no prognostic biomarkers have been identified in this setting. We retrospectively analyzed the expression of progesterone receptor (PR) and Ki67, assessed by immunohistochemistry, in 71 ABC patients treated with CDK4/6i and analyzed the impact of these markers on progression-free survival (PFS). The majority of patients 63/71 (88.7%) received palbociclib, 4 (5.6%) received ribociclib, and 4 (5.6%) received abemaciclib. A higher median value of Ki67 was observed in cases undergoing second-line treatment (p = 0.047), whereas the luminal B subtype was more prevalent (p = 0.005). In the univariate analysis of the first-line setting, luminal A subtype showed a trend towards a correlation with a longer PFS (p = 0.053). A higher continuous Ki67 value led to a significantly shorter PFS. When the interaction between pathological characteristics and line of treatment was considered, luminal B subtype showed a significantly (p = 0.043) worse outcome (Hazard Ratio (HR) 2.84; 1.03–7.82 95% Confidence Interval (CI)). PFS in patients undergoing endocrine therapy plus CDK4/6i was inversely correlated with Ki67 expression but not with PR, suggesting that tumor proliferation has a greater impact on cell cycle inhibitors combined with endocrine therapy than PR expression.

Network and data integration for biomarker signature discovery via network smoothed T-statistics

Predictive, stable and interpretable gene signatures are generally seen as an important step towards a better personalized medicine. During the last decade various methods have been proposed for that purpose. However, one important obstacle for making gene signatures a standard tool in clinics is the typical low reproducibility of signatures combined with the difficulty to achieve a clear biological interpretation. For that purpose in the last years there has been a growing interest in approaches that try to integrate information from molecular interaction networks. We here propose a technique that integrates network information as well as different kinds of experimental data (here exemplified by mRNA and miRNA expression) into one classifier. This is done by smoothing t-statistics of individual genes or miRNAs over the structure of a combined protein-protein interaction (PPI) and miRNA-target gene network. A permutation test is conducted to select features in a highly consistent manner, and subsequently a Support Vector Machine (SVM) classifier is trained. Compared to several other competing methods our algorithm reveals an overall better prediction performance for early versus late disease relapse and a higher signature stability. Moreover, obtained gene lists can be clearly associated to biological knowledge, such as known disease genes and KEGG pathways. We demonstrate that our data integration strategy can improve classification performance compared to using a single data source only. Our method, called stSVM, is available in R-package netClass on CRAN (http://cran.r-project.org).

Targeting Rb inactivation in cancers by synthetic lethality

The retinoblastoma protein, pRb, is a key regulator of cell proliferation, differentiation, apoptosis, as well as checkpoint and stress responses. The function of Rb is often inactivated in many types of cancers, a feature that can potentially be used to target this specific subset of cancers. However little is known about how the loss of Rb function can be exploited in cancer therapies. In this review, we overview the functions of Rb, and discuss a genetic screen that led to the finding that inactivation of TSC2 and Rb induces synergistic cell death in both Drosophila developing tissues and human cancer cells. The mechanisms for synergistic cell death involve the accumulation of cellular stress, suggesting that inactivation of TSC2 and chemotherapeutic agents that result in induction of cellular stress can potentially be combined to treat cancers harboring inactivated Rb.

RB1CC1 together with RB1 and p53 predicts long-term survival in Japanese breast cancer patients

RB1-inducible coiled-coil 1 (RB1CC1) plays a significant role in the enhancement of the retinoblastoma tumor suppressor (RB1) pathway and is involved in breast cancer development. However, RB1CC1's role in clinical progression of breast cancer has not yet been evaluated, so, as a first step, it is necessary to establish its usefulness as a tool to evaluate breast cancer patients. In this report, we have analyzed the correlation between abnormalities in the RB1CC1 pathway and long-term prognosis, because disease-specific death in later periods (>5 years) of the disease is a serious problem in breast cancer. Breast cancer tissues from a large cohort in Japan were evaluated by conventional immunohistochemical methods for the presence of the molecules involved in the RB1CC1 pathway, including RB1CC1, RB1, p53, and other well-known prognostic markers for breast cancer, such as estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The correlation between the immunohistochemical results and clinical outcomes of 323 breast cancer patients was analyzed using a Kaplan-Meier log-rank test and a multivariate Cox proportional hazards regression analysis. Absence of nuclear RB1CC1 expression was associated with the worst prognosis (Log-rank test, Chi-Square value = 17.462, p<0.0001). Dysfunction of either one of RB1CC1, RB1, or p53 was associated with the highest risk for cancer-specific death, especially related to survival lasting more than 5 years (multivariate Cox proportional hazard ratio = 3.951, 95% Confidence Interval = 1.566–9.967, p = 0.0036). Our present data demonstrate that the combined evaluation of RB1CC1, RB1 and p53 by conventional immunohistochemical analysis provides an accurate prediction of the long-term prognoses of breast cancer patients, which can be carried out as a routine clinical examination.

Cellular quiescence in mammary stem cells and breast tumor stem cells: got testable hypotheses?

Cellular quiescence is a state of reversible cell cycle arrest and has more recently been shown to be a blockade to differentiation and to correlate with resistance to cancer chemotherapeutics and other xenobiotics; features that are common to adult stem cells and possibly tumor stem cells. The biphasic kinetics of mammary regeneration, coupled to its cyclic endocrine control suggest that mammary stem cells most likely divide during a narrow window of the regenerative cycle and return to a state of quiescence. This would enable them to retain their proliferative capacity, resist differentiation signals and preserve their prolonged life span. There is accumulating evidence that mammary stem cells and other adult stem cells utilize quiescence for this purpose, however the degree to which tumor stem cells do so is largely unknown. The retained proliferative capacity of mammary stem cells likely enables them to accumulate and harbor mutations that lead to breast cancer initiation. However it is currently unclear if these causative lesions lead to defective or deranged quiescence in mammary stem cells. Evidence of such effects could potentially lead to the development of diagnostic systems that monitor mammary stem cell quiescence or activation. Such systems may be useful for the evaluation of patients who are at significant risk of breast cancer. Additionally quiescence has been postulated to contribute to therapeutic resistance and tumor recurrence. This review aims to evaluate what is known about the mechanisms governing cellular quiescence and the role of tumor stem cell quiescence in breast cancer recurrence.

Most basal-like breast carcinomas demonstrate the same Rb-/p16+ immunophenotype as the HPV-related poorly differentiated squamous cell carcinomas which they resemble morphologically

Basal-like carcinomas (BLCs) of the breast share discriminatory morphologic features with poorly differentiated high-risk human papilloma virus (HPV)-related squamous cell carcinomas of the oropharynx, penis, and vulva. Because HPV E7 protein inactivates the retinoblastoma (Rb) protein, diffuse p16 expression is a surrogate marker for these high-risk HPV-related carcinomas. HPV E6 protein also inactivates p53, further compromising the G1-S cell cycle checkpoint. The Rb/p16/p53 immunohistochemical profile of BLC of the breast has not been well characterized. Tissue microarrays containing 71 invasive ductal carcinomas (IDCs) of the breast were immunolabeled for p16, Rb, p53, and Ki-67. The cases included 4 distinct groups of IDCs having surrogate immunohistochemical profiles corresponding to categories defined by gene expression profiling (17 luminal A, 7 luminal B, 14 HER-2+, and 21 BLC), along with 12 unclassifiable triple negative carcinomas (UTNCs). Twenty-five of the 71 IDC were Rb negative/p16 diffuse positive (Rb-/p16+). These included 15 of 21 BLC and 9 of 12 UTNC, but only 1 of 14 HER-2 positive cases and none of the 17 luminal A or 7 luminal B cases (P<0.01, BLC or UTNC vs. others). Six of the Rb-/p16+ IDC also had a significant ductal carcinoma in situ component. The ductal carcinoma in situ in 4 of these 6 cases showed the same Rb-/p16+ phenotype as the associated IDC. BLC and UTNC had the highest Ki-67 indices of the 5 groups, even when matched for grade. The Rb-/p16+ phenotype and the Rb-/p16+/p53 overexpressing phenotype correlated with increased proliferation within the BLC group. In conclusion, BLC and UTNC, but not HER-2, luminal A, or luminal B carcinomas, frequently demonstrate an Rb-/p16+ phenotype, similar to the HPV-related squamous cell carcinomas that BLC resemble morphologically. This subset may represent a more homogenous group than BLC as defined currently.

Tailoring to RB: tumour suppressor status and therapeutic response

The retinoblastoma tumour suppressor (RB) is a crucial regulator of cell-cycle progression that is invoked in response to a myriad of anti-mitogenic signals. It has been hypothesized that perturbations of the RB pathway confer a synonymous proliferative advantage to tumour cells; however, recent findings demonstrate context-specific outcomes associated with such lesions. Particularly, loss of RB function is associated with differential response to wide-ranging therapeutic agents. Thus, the status of this tumour suppressor may be particularly informative in directing treatment regimens.

Growth suppression and radiosensitivity increase by HMGB1 in breast cancer

AIM

HMGB1 (high-mobility group box-1) is a nuclear protein containing a consensus RB (retinoblastoma)-binding LXCXE motif. In this study, we studied the potential association of HMGB1 and RB and the in vitro and in vivo activities of HMGB1 in human breast cancer cells.

METHODS

The protein-protein interaction was determined by immunoprecipitation-Western blotting and glutathione-S-transferase capture assays; cell growth and radiosensitivity were examined by cell counts, MTT assay, and clonogenic assay; cell cycle progression and apoptosis were evaluated using flow cytometry; and the antitumor activity of HMGB1 was examined with tumor xenografts in nude mice.

RESULTS

HMGB1 was associated with RB via a LXCXE motif-dependent mechanism. HMGB1 enhanced the ability of RB for E2F and cyclin A transcription repression. The increased expression of HMGB1 conferred an altered phenotypes characterized by the suppression of cell growth; G1 arrest and apoptosis was induced in MCF-7 cells containing the wild-type retinoblastoma (Rb) gene, but showed no activities in BT-549 cells containing the Rb gene deletion. The HMGB1-induced apoptosis accompanied by caspase 3 activation and PARP (poly(ADP-ribose)polymerase) cleavage. HMGB1 elevated the radiosensitivity of breast cancer cells in both the MCF-7 and BT-549 cell lines. The enhanced expression of HMGB1 caused a suppression of growth of MCF-7 tumor xenografts in nude mice, while LXCXE-defective HMGB1 completely lost antitumor growth activity.

CONCLUSION

HMGB1 functions as a tumor suppressor and radiosensitizer in breast cancer. A HMGB1-RB interaction is critical for the HMGB1-mediated transcriptional repression, cell growth inhibition, G1 cell cycle arrest, apoptosis induction, and tumor growth suppression, but is not required for radiosensitization. Therefore, it may be possible to design new therapies for the treatment of breast cancer that exert their effects by modulating the HMGB1 and RB regulatory pathway and HMGB1-related gene therapy.

Epithelial cell proliferation contributes to airway remodeling in severe asthma

RATIONALE

Despite long-term therapy with corticosteroids, patients with severe asthma develop irreversible airway obstruction.

OBJECTIVES

To evaluate if there are structural and functional differences in the airway epithelium in severe asthma associated with airway remodeling.

METHODS

In bronchial biopsies from 21 normal subjects, 11 subjects with chronic bronchitis, 9 subjects with mild asthma, and 31 subjects with severe asthma, we evaluated epithelial cell morphology: epithelial thickness, lamina reticularis (LR) thickness, and epithelial desquamation. Levels of retinoblastoma protein (Rb), Ki67, and Bcl-2 were measured, reflecting cellular proliferation and death. Terminal deoxynucleotidyl-mediated dUTP nick end labeling (TUNEL) was used to study cellular apoptosis.

MEASUREMENTS AND MAIN RESULTS

Airway epithelial and LR thickness was greater in subjects with severe asthma compared with those with mild asthma, normal subjects, and diseased control subjects (p=0.009 and 0.033, respectively). There was no significant difference in epithelial desquamation between groups. Active, hypophosphorylated Rb expression was decreased (p=0.002) and Ki67 was increased (p<0.01) in the epithelium of subjects with severe asthma as compared with normal subjects, indicating increased cellular proliferation. Bcl-2 expression was decreased (p<0.001), indicating decreased cell death suppression. There was a greater level of apoptotic activity in the airway biopsy in subjects with severe asthma as compared with the normal subjects using the TUNEL assay (p=0.002), suggesting increased cell death.

CONCLUSIONS

In subjects with severe asthma, as compared with subjects with mild asthma, normal subjects, and diseased control subjects, we found novel evidence of increased cellular proliferation in the airway contributing to a thickened epithelium and LR. These changes may contribute to the progressive decline in lung function and airway remodeling in patients with severe asthma.

The retinoblastoma tumor suppressor modifies the therapeutic response of breast cancer

The retinoblastoma tumor suppressor (RB) protein is functionally inactivated in the majority of human cancers and is aberrant in one-third of all breast cancers. RB regulates G(1)/S-phase cell-cycle progression and is a critical mediator of antiproliferative signaling. Here the specific impact of RB deficiency on E2F-regulated gene expression, tumorigenic proliferation, and the response to 2 distinct lines of therapy was investigated in breast cancer cells. RB knockdown resulted in RB/E2F target gene deregulation and accelerated tumorigenic proliferation, thereby demonstrating that even in the context of a complex tumor cell genome, RB status exerts significant control over proliferation. Furthermore, the RB deficiency compromised the short-term cell-cycle inhibition following cisplatin, ionizing radiation, and antiestrogen therapy. In the context of DNA-damaging agents, this bypass resulted in increased sensitivity to these agents in cell culture and xenograft models. In contrast, the bypass of antiestrogen signaling resulted in continued proliferation and xenograft tumor growth in the presence of tamoxifen. These effects of aberrations in RB function were recapitulated by ectopic E2F expression, indicating that control of downstream target genes was an important determinant of the observed responses. Specific analyses of an RB gene expression signature in 60 human patients indicated that deregulation of this pathway was associated with early recurrence following tamoxifen monotherapy. Thus, because the RB pathway is a critical determinant of tumorigenic proliferation and differential therapeutic response, it may represent a critical basis for directing therapy in the treatment of breast cancer.

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.

RB family members as predictive and prognostic factors in human cancer

The retinoblastoma family members--pRb, pRb2/p130 and p107--are tumor suppressor genes involved in controlling four major cellular processes: growth arrest, apoptosis, differentiation and angiogenesis. Molecular genetic studies have identified abnormalities of these tumor suppressor genes in a large proportion of human cancers. These genetic alterations have emerged as significant factors in the pathogenesis and progression of many types of tumors and are therefore likely to provide relevant information to assess risk in cancer patients. There is a pressing clinical need to identify prognostic and predictive factors for patients with cancer, because there is an undeniable importance in being able to determine which patients will have a favorable outcome without further therapy (prognostic factor) and which will need some additional treatment (predictive factor). This review examines the predictive and/or prognostic role of each retinoblastoma family member in human cancer.

Expression of retinoblastoma protein in breast cancer metastases to sentinel nodes: evaluation of its role as a marker for the presence of metastases in non-sentinel axillary nodes, and comparison to p16INK4a

The aim of this study was to evaluate the role of retinoblastoma protein (pRb), alone and in combination with p16, as a predictive marker for metastases in non-sentinel nodes in cases where the sentinel node showed metastatic breast carcinoma. Paraffin blocks of lymph nodes from 48 patients with metastatic breast carcinoma were immunostained with a monoclonal antibody to retinoblastoma protein (PharMingen). Results were compared with known prognostic parameters of the primary tumor, estrogen and progesterone receptor status, proliferation index, and p16 (DAKO) expression. Lymph nodes from 38 of the 48 (79%) cases were pRb positive. There was no correlation of pRb staining alone with the primary tumor parameters studied or the proliferative index of the metastatic tumor. In 16 patients with both a sentinel node biopsy and an axillary lymph node dissection, 8 (50%) had metastatic breast carcinoma. The sentinel nodes of three of these eight patients (38%) were pRb negative (positive predictive value of 60% vs. 73% for p16). The remaining eight patients (50%) had no metastases in non-sentinel nodes, even though their sentinel nodes had metastatic breast carcinoma; six of these eight patients (75%) were pRb positive (negative predictive value of 55% vs. 83% for p16). pRb and p16 staining results combined showed that pRb-negative/p16-positive cases were associated with non-sentinel node metastases (positive predictive value of 100%) as well as poor prognostic parameters. Patients with the opposite staining profile (pRb positive and p16 negative) were mostly without non-sentinel node metastases (negative predictive value of 75%). Cases negative for both pRb and p16 were consistently associated with a better prognostic phenotype and absence of additional axillary node metastases. In conclusion, the presence or absence of pRb in sentinel nodes is of little predictive value for non-sentinel node metastases unless taken in conjunction with the presence of p16 staining. Instead, it appears to enhance the positive predictive value of p16 in determining the presence of non-sentinel node metastases. Due to the limited subgroup sample size in this study, clinical guidelines cannot be suggested as yet, but further research focused on the pRb-negative/p16-positivie and pRb-negative/p16-negative phenotypes may yield beneficial results.

Suppressor of cytokine signalling 2 (SOCS-2) expression in breast carcinoma

AIMS

To investigate SOCS-2 (suppressor of cytokine signalling 2) protein expression in breast carcinoma samples in relation to biopathological parameters and survival.

METHODS

A polyclonal antibody against SOCS-2 was used to study 50 archival breast carcinoma samples, collected from 1993 to 1995. The presence of SOCS-2 protein was investigated in relation to clinical and biological parameters used in breast cancer pathology. Fluorescence in situ hybridisation (FISH) was used to study whether SOCS-2 expression was related to SOCS-2 gene copy number.

RESULTS

SOCS-2 protein was expressed in 34 of 50 breast carcinoma samples and was positively associated with low grade, low nuclear grade, and p27 protein. SOCS-2 expression was inversely related to Ki-67, cyclin A, retinoblastoma protein (pRb), and the epidermal growth factor receptor (EGFR). No relation with overall survival was demonstrated. SOCS-2 amplification was found in three samples. No relation between the number of FISH signals and SOCS-2 expression was found.

CONCLUSIONS

The significant correlation seen between SOCS-2 expression, grade, nuclear grade, p27, Ki-67, cyclin A, pRb, and EGFR labelling strongly supports the hypothesis that SOCS-2 loss might be related to cell proliferation and tumour growth in breast carcinoma. Gene copy number changes did not seem to play a role in SOCS-2 regulation and expression; other mechanisms might be involved and deserve further study.

Simultaneous chromosome 1q gain and 16q loss is associated with steroid receptor presence and low proliferation in breast carcinoma

We applied comparative genomic hybridization (CGH) to 46 breast carcinoma samples, collected from 1993 to 1995, in order to detect chromosome 1q gains and 16q losses and to define whether samples showing both these alterations had distinct biopathologic features and different clinical outcome. A total of 22 samples (48%) had simultaneous chromosome 1q gain and 16q loss, which was always associated with other genetic changes. In total, 23 samples had various chromosome imbalances (including chromosome 1q gain independent of chromosome 16q loss and vice versa) and one sample did not show detectable alterations. Samples having chromosome 1q gain/16q loss were compared to the other samples with regard to neoplasm size, lymph-node status, histologic and nuclear grade, estrogen and progesterone receptor presence, Ki-67, pRB, Cyclin D1, Cyclin A, p53, p21 and p27 expression as detected by immunohistochemistry. The samples showing chromosome 1q gain/16q loss had high steroid hormone receptor expression (P=0.02), low cell growth fraction (Ki-67, P=0.03) and high p27 expression (P<0.001). No statistical correlation with disease-free survival and overall survival or response to hormonal therapy was found. We conclude that simultaneous chromosome 1q gain/16q loss is a frequent event in invasive breast cancer, which occurs in a subset of both intermediate- and high-grade breast carcinomas. Although the final chromosome 1q and 16q imbalances might have originated from different chromosome alterations in low- and high-grade samples, the gene-dosage effect might be important in conferring peculiar biopathologic characteristics to this subset of samples. The cytogenetic and molecular mechanisms underlying these chromosome changes deserve further investigations.

An immunohistochemical study of retinoblastoma gene product in normal, premalignant and malignant tissues of the uterine cervix

The retinoblastoma gene was the first tumour suppressor gene identified that was altered not only in retinoblastomas but has been described in a wide variety of human neoplasms. The retinoblastoma gene encodes a nuclear phosphoprotein that in its hypophosphorylated state plays an important role in regulating the cell cycle, thus preventing from tumour formation. Expression of retinoblastoma gene protein product (pRB) was investigated in 118 formalin-fixed, paraffin-embedded cervical tissues by immunohistochemistry using commercially available antibody directed against RB protein. Ten normal ectocervical epithelium, 16 cervical intraepithelial neoplasia (CIN) I, 13 CIN II, 14 CIN III, 53 invasive squamous cell carcinoma, 11 adenocarcinoma and 1 small cell carcinoma were selected for this study. The proportions of pRB-positive cells as well as the extent of pRB expression in ectocervical squamous epithelium were assessed and compared among the lesions. The pRB expression was observed in 100% of normal ectocervical epithelium (n=10), 100% of CIN lesions (n=43) and 98.5% of invasive carcinoma of the uterine cervix (n=65) and were statistically significant when CIN or CIN/invasive were compared to normal cases (P < 0.01, P < 0.05 respectively). While in invasive squamous cell carcinoma (SCC), 81.8% (9/11) pRB-positive cells were found in much higher percentages in well differentiated SCC compared to 64.3% (18/28) of moderately differentiated cases and only 7.1% (1/14) of poorly differentiated SCC (P < 0.01, respectively). The results of this study suggest that loss of RB protein expression is rare in carcinoma of the uterine cervix and this protein may be important in the pathogenesis of cervical carcinoma.

Reduced growth rate accompanied by aberrant epidermal growth factor signaling in drug resistant human breast cancer cells

We examined transforming growth factor (TGF) alpha, epidermal growth factor (EGF) and EGF receptor (EGFR) expression and signaling in three drug resistant MCF-7 human breast cancer sublines and asked whether these pathways contribute to the drug resistance phenotype. In the resistant sublines, upregulation of both TGFalpha and EGFR mRNA was observed. In an apparent contrast with upregulated growth factor and receptor gene expression, the drug resistant sublines displayed a reduced growth rate. Defects in the EGFR signaling pathway cascade were found in all examined drug resistant sublines, including altered EGF-induced Shc, Raf-1, or mitogen-activated protein kinase phosphorylation. Induction of c-fos mRNA expression by EGF was impaired in the sublines compared to parental MCF-7 cells. In contrast, the induction of the stress-activated protein kinase activity was similar in both parental and drug resistant cells. Evaluating the link between the reduced growth rate and drug resistance, serum starvation experiments were performed. These studies demonstrated that a reduced proliferative activity resulted in a marked reduction in sensitivity to cytotoxic agents in the parental MCF-7 cells. We propose that the altered EGFR levels frequently observed in drug resistant breast cancer cells are associated with perturbations in the signaling pathway that mediate a reduced proliferative rate and thereby contribute to drug resistance.

Clinical significance of retinoblastoma protein (pRB) expression in esophageal squamous cell carcinoma

BACKGROUND AND OBJECTIVES

The goal was to evaluate the clinicopathological significance of retinoblastoma gene product (pRB) expression in esophageal squamous cell carcinoma.

METHODS

We investigated abnormal pRB expression in tumors in 191 patients using an immunohistochemical method in conjunction with anti-RB protein antibody. Surgically resected esophageal squamous cell carcinomas were examined by immunohistochemical analysis for altered pRB expression.

RESULTS

Decreased pRB nuclear staining indicating loss of RB function occurred in 82 (43%) of the cases studied. The incidence of decreased pRB expression was higher in tumors with invasion to the adventitia (50%) than in tumors without invasion to the adventitia (33%, P = 0.0188). In addition, the incidence of decreased pRB expression was higher in tumors with lymph node metastasis (50%) than in those without (34%, P = 0.0346). The 3-year survival rates of 82 patients who had tumors with decreased pRB expression (30%) was significantly lower than that of 109 patients who had tumors with normal pRB expression (52%, P = 0.0032). However, in the multivariate survival analysis, pRB expression was not an independent prognostic factor for patients with esophageal squamous cell carcinoma.

CONCLUSIONS

Abnormal pRB expression appears to be closely associated with tumor development. However, the existence of tumors with hyperphosphorylated RB protein (inactivated form) in pRB-positive tumors, such as those in the present study, should be considered. Thus, discrimination of this hyperphosphorylated form of RB protein from the unphosphorylated RB protein is needed.