Normal Control Breast Research Articles

Aberrant Promoter Methylation of the Tumour Suppressor RASSF10 and Its Growth Inhibitory Function in Breast Cancer.

Breast cancer is the most common cancer in women, with 1.7 million new cases each year. As early diagnosis and prognosis are crucial factors in cancer treatment, we investigated potential DNA methylation biomarkers of the tumour suppressor family Ras-association domain family (RASSF). Promoter hypermethylation of tumour suppressors leads to their inactivation and thereby promotes cancer development and progression. In this study we analysed the tumour suppressors RASSF1A and RASSF10. Our study shows that RASSF10 is expressed in normal breast but inactivated by methylation in breast cancer. We observed a significant inactivating promoter methylation of RASSF10 in primary breast tumours. RASSF10 is inactivated in 63% of primary breast cancer samples but only 4% of normal control breast tissue is methylated (p < 0.005). RASSF1A also shows high promoter methylation levels in breast cancer of 56% vs. 8% of normal tissue (p < 0.005). Interestingly more than 80% of breast cancer samples harboured a hypermethylation of RASSF10 and/or RASSF1A promoter. Matching samples exhibited a strong tumour specific promoter methylation of RASSF10 in comparison to the normal control breast tissue. Demethylation treatment of breast cancer cell lines MCF7 and T47D reversed RASSF10 promoter hypermethylation and re-established RASSF10 expression. In addition, we could show the growth inhibitory potential of RASSF10 in breast cancer cell lines MCF7 and T47D upon exogenous expression of RASSF10 by colony formation. We could further show, that RASSF10 induced apoptotic changes in MCF7 and T47D cells, which was verified by a significant increase in the apoptotic sub G1 fraction by 50% using flow cytometry for MCF7 cells. In summary, our study shows the breast tumour specific inactivation of RASSF10 and RASSF1A due to DNA methylation of their CpG island promoters. Furthermore RASSF10 was characterised by the ability to block growth of breast cancer cell lines by apoptosis induction.

Loss of LKB1 disrupts breast epithelial cell polarity and promotes breast cancer metastasis and invasion.

BackgroundLKB1, also known as STK11, is a master kinase that serves as an energy metabolic sensor and is involved in cell polarity regulation. Recent studies have indicated that LKB1 is related to breast tumorigenesis and breast cancer progression. However, little work has been done on the roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer. In this study, we tried to prove that loss of LKB1 disrupts breast epithelial cell polarity and causes tumor metastasis and invasion.MethodsThe relationships of LKB1 expression to clinic-pathological parameters and epithelial markers E-cadherin and high-molecular-weight -cytokeratin (HMW-CK) were investigated in 80 clinical breast cancer tissue samples and their paired normal control breast tissue samples by using immunohistochemistry. Then, the LKB1 expressions in metastatic and non-metastatic breast cancer cell lines were compared. The roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer were determined by using immunofluorescence, western blot assay, and cell migration and invasive assays. Finally, the non-transformed human breast cell line MCF-10A was cultured in three dimensions to further reveal the role of LKB1 in breast epithelial cell polarity maintenance.ResultsHistopathological analysis showed that LKB1 expression level was significantly negatively correlated with breast cancer TNM stage, and positively correlated with ER/PR status and expression levels of E-cadherin and HMW-CK. Immunofluorescence staining showed that LKB1 was co-localized with E-cadherin at adheren junctions. In vitro analysis revealed that loss of LKB1 expression enhanced migration, invasion and the acquisition of mesenchymal phenotype, while LKB1 overexpression in MDA-MB-435 s cells, which have a low basal level of LKB1 expression, promoted the acquisition of epithelial phenotype. Finally, it was found for the first time that endogenous LKB1 knockdown resulted in abnormal cell polarity in acini formed by non-transformed breast epithelial cells grown in 3D culture.ConclusionOur data indicated that low expression of LKB1 was significantly associated with established markers of unfavorable breast cancer prognosis, such as loss of ER/PR, E-cadherin and HMW-CK. Knockdown of endogenous LKB1 gave rise to dysregulation of cell polarity and invasive phenotype of breast cancer cells.

Loss of LKB1 disrupts breast epithelial cell polarity and promotes breast cancer metastasis and invasion

LKB1, also known as STK11, is a master kinase that serves as an energy metabolic sensor and is involved in cell polarity regulation. Recent studies have indicated that LKB1 is related to breast tumorigenesis and breast cancer progression. However, little work has been done on the roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer. In this study, we tried to prove that loss of LKB1 disrupts breast epithelial cell polarity and causes tumor metastasis and invasion. The relationships of LKB1 expression to clinic-pathological parameters and epithelial markers E-cadherin and high-molecular-weight -cytokeratin (HMW-CK) were investigated in 80 clinical breast cancer tissue samples and their paired normal control breast tissue samples by using immunohistochemistry. Then, the LKB1 expressions in metastatic and non-metastatic breast cancer cell lines were compared. The roles of LKB1 in cell polarity and epithelial-mesenchymal transition in breast cancer were determined by using immunofluorescence, western blot assay, and cell migration and invasive assays. Finally, the non-transformed human breast cell line MCF-10A was cultured in three dimensions to further reveal the role of LKB1 in breast epithelial cell polarity maintenance. Histopathological analysis showed that LKB1 expression level was significantly negatively correlated with breast cancer TNM stage, and positively correlated with ER/PR status and expression levels of E-cadherin and HMW-CK. Immunofluorescence staining showed that LKB1 was co-localized with E-cadherin at adheren junctions. In vitro analysis revealed that loss of LKB1 expression enhanced migration, invasion and the acquisition of mesenchymal phenotype, while LKB1 overexpression in MDA-MB-435 s cells, which have a low basal level of LKB1 expression, promoted the acquisition of epithelial phenotype. Finally, it was found for the first time that endogenous LKB1 knockdown resulted in abnormal cell polarity in acini formed by non-transformed breast epithelial cells grown in 3D culture. Our data indicated that low expression of LKB1 was significantly associated with established markers of unfavorable breast cancer prognosis, such as loss of ER/PR, E-cadherin and HMW-CK. Knockdown of endogenous LKB1 gave rise to dysregulation of cell polarity and invasive phenotype of breast cancer cells.

Promoter methylation and expression changes of CDH1 and P16 genes in invasive breast cancer and adjacent normal breast tissue

We studied the promoter methylation status and expression levels of P16 and CDH1 genes in breast cancer and their adjacent normal tissues with normal control breast tissues, to correlate with their histopathological parameters. Hundred twenty four samples (tumor and adjacent nonmalignant tissues) from 62 breast cancer patients and 4 normal control breast tissues were included in the study. We used methylation specific PCR to evaluate methylation status and quantitative RT-PCR to measure the gene expression levels. Methylation incidence of P16 gene and CDH1 gene in tumor tissues were 24.2 % and 33.9 %, respectively. CDH1 and P16 gene were not methylated in normal control tissues. CDH1 underexpression is found to be significant in correlation with advanced stage, histologic type, high tumor grade and lymph node involvement. P16 expression is found not to be significantly related with any histopathological parameters. But 60% of cases which overexpresses P16 were estrogen negative, and 40% of them were histologic grade 3. Both P16 and CDH1 had different expression levels in tumor tissues compared to the adjacent normal tissues and in adjacent normal tissues compared to the normal non-tumor tissues.

A TCRMimic Monoclonal Antibody Generated from a Directly Discovered Epitope of p68 RNA Helicase Dramatically Debulks Large Established Tumors through Recognition of a Specific MHC/Peptide Complex.

Abstract Debulking large tumors using monoclonal antibodies (mAb) that specifically recognize unique T cell epitopes represents a novel approach to cancer therapy.Using a mAb designated as a TCRm we recently demonstrated the in vivo suppression of tumor growth. The TCRm had specificity for a peptide/MHC class I molecule expressed on the surface of the tumor cells. In this study we use an innovative direct epitope discovery strategy that led to the identification of peptide YLLPAIVHI in the context of HLA-A*0201 (YLL/A2) in human breast carcinoma cell lines. The peptide is derived from the DEAD Box RNA helicase protein p68, a protein overexpressed and highly phosphorylated in malignant cells. A TCRm antibody (RL6A) was generated and characterized for binding specificity, sensitivity and affinity for the YLL/A2 target. The TCRm specifically stained cells that co-expressed HLA-A2 and p68 but not cells lacking expression of p68 protein or HLA-A2 alone. It binds to cognate peptide/HLA-A2 with an affinity constant (KD) of 5.69 x 10-10 M and recognized specifically the YLL/A2 epitope in human breast cancer tissue but not in normal control breast tissue.Mice implanted in the mammary fat pad with human breast tumor cells grew tumors of considerable size, yet when treated with RL6A TCRm there was a marked reduction in tumor size. Examination of frozen tumor tissue sections revealed significantly greater numbers of apoptotic cells in mice treated with RL6A TCRm than with control antibody. Investigation in vitro showed that TCRm engagement of specific YLL/A2 epitope led to the induction of apoptosis providing the first experimental evidence that MHC signaling could directly mediate tumor cell death. Together, these data indicate that TCRm targeting of specific peptide/MHC complexes unique to tumor cells is effective not only in slowing the growth of tumors but also in dramatically reducing the size of established tumors and suggests a possible novel approach to the treatment of cancer. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5072.

Direct discovery and validation of a peptide/MHC epitope expressed in primary human breast cancer cells using a TCRm monoclonal antibody with profound antitumor properties.

The identification and validation of new cancer-specific T cell epitopes continues to be a major area of research interest. Nevertheless, challenges remain to develop strategies that can easily discover and validate epitopes expressed in primary cancer cells. Regarded as targets for T cells, peptides presented in the context of the major histocompatibility complex (MHC) are recognized by monoclonal antibodies (mAbs). These mAbs are of special importance as they lend themselves to the detection of epitopes expressed in primary tumor cells. Here, we use an approach that has been successfully utilized in two different infectious disease applications (WNV and influenza). A direct peptide-epitope discovery strategy involving mass spectrometric analysis led to the identification of peptide YLLPAIVHI in the context of MHC A*02 allele (YLL/A2) from human breast carcinoma cell lines. We then generated and characterized an anti-YLL/A2 mAb designated as RL6A TCRm. Subsequently, the TCRm mAb was used to directly validate YLL/A2 epitope expression in human breast cancer tissue, but not in normal control breast tissue. Moreover, mice implanted with human breast cancer cells grew tumors, yet when treated with RL6A TCRm showed a marked reduction in tumor size. These data demonstrate for the first time a coordinated direct discovery and validation strategy that identified a peptide/MHC complex on primary tumor cells for antibody targeting and provide a novel approach to cancer immunotherapy.

Immunohistochemical Analysis of MUC5B Apomucin Expression in Breast Cancer and Non-malignant Breast Tissues

A deregulation of several MUC genes (MUC1, MUC2, MUC3, MUC5AC, and MUC6) was previously demonstrated in breast carcinomas. Considering that recently we found the "non-mammary" MUC5B mRNA in primary breast tumors (Berois et al. 2003), we undertook the present study to evaluate the expression profile of MUC5B protein product in breast tissues, using LUM5B-2 antisera raised against sequences within the non-glycosylated regions of this apomucin. Expression of MUC5B by breast cancer cells was confirmed by immunocytochemistry, in situ hybridization, and Western blot on MCF-7 cancer cells. Using an immunohistochemical procedure, MUC5B apomucin was detected in 34/42 (81%) primary breast tumors, in 13/14 (92.8%) samples of non-malignant breast diseases, in 8/19 (42.1%) samples of normal-appearing breast epithelia adjacent to cancer, and in 0/5 normal control breast samples. The staining pattern of MUC5B was very different when comparing breast cancer cells (cytoplasmic) and non-malignant breast cells (predominantly apical and in the secretory material). We analyzed MUC5B mRNA expression using RT-PCR in bone marrow aspirates from 22/42 patients with breast cancer to compare with MUC5B protein expression in the primary tumors. Good correlation was observed because the six MUC5B-positive bone marrow samples also displayed MUC5B expression in the tumor. Our results show, for the first time at the protein level, that MUC5B apomucin is upregulated in breast cancer. Its characterization could provide new insights about the glycobiology of breast cancer cells.

Identification of Protein-tyrosine Phosphatase 1B as the Major Tyrosine Phosphatase Activity Capable of Dephosphorylating and Activating c-Src in Several Human Breast Cancer Cell Lines

c-Src tyrosine kinase activity is elevated in several types of human cancer, and this has been attributed to elevated c-Src expression levels, increased c-Src specific activity, and activating mutations in c-Src. We have found a number of human breast cancer cell lines with elevated c-Src specific activity that also possess elevated phosphatase activity directed against the carboxyl-terminal negative regulatory domain of Src family kinases. To identify this phosphatase, cell extracts from MDA-MB-435S cells were chromatographed and the fractions were assayed for phosphatase activity. Four peaks of phosphatase activity directed against the nonspecific substrate poly(Glu/Tyr) were detected. One peak also dephosphorylated a peptide modeled against the c-Src carboxyl-terminal negative regulatory domain and intact human c-Src. Immunoblotting and immunodepletion experiments identified the phosphatase as protein-tyrosine phosphatase 1B (PTP1B). Examination of several human breast cancer cell lines with increased c-Src activity showed elevated levels of PTP1B protein relative to normal control breast cells. In vitro c-Src reactivation experiments confirmed the ability of PTP1B to dephosphorylate and activate c-Src. In vivo overexpression of PTP1B in 293 cells caused a 2-fold increase of endogenous c-Src kinase activity. Our findings indicate that PTP1B is the primary protein-tyrosine phosphatase capable of dephosphorylating c-Src in several human breast cancer cell lines and suggests a regulatory role for PTP1B in the control of c-Src kinase activity.

ANALYSIS OF BREAST-TISSUE CATHEPSIN-D ISOFORMS FROM PATIENTS WITH BREAST-CANCER, BENIGN BREAST DISEASE AND FROM NORMAL CONTROLS

The isoform composition of cathepsin D has been investigated by isoelectric focusing of breast tissue supernatant fluids from patients with breast cancer, benign breast disease and from normal controls. The results indicated the presence of several acid protease isoforms between pi values of 2 to 8. Three of these isoforms (with approximate pIs of 6.0, 6.4 and 7.0) were pepstatin-inhibitable but not inhibitable by a mixture of protease inhibitors for seryl, cysteinyl and metalloproteases. These three isoforms, and not the more acidic isoforms, contained a 31 kD protein band which was recognized by polyclonal antibodies against cathepsin D, suggesting that these isoforms are cathepsin D. Further evidence that these isoforms are cathepsin D came from studies in which the pepstatin-inhibitable protease activity and not the pepstatin-uninhibitable protease activity, bound to and was elutable from, an immunoaffinity resin made by coupling anticathepsin D polyclonal antibodies to agarose. The mean relative percentage of the total breast tissue protease activity associated with pepstatin-inhibitable activity (i.e. cathepsin D) was significantly increased (p<0.01) in five breast cancer isoform profiles (64+/-4%, mean+/-S.D.) when compared to five normal control breast profiles (32+/-5%). An analysis of the three cathepsin D isoforms between pIs 6 to 7 indicated a trend of increased relative amounts of the most acidic isoform in the breast cancer isoform profiles when compared to isoform profiles from benign breast disease and normal control breast tissues. Evidence that the more acidic cathepsin D isoforms are related to the more neutral isoforms by sialylation came from studies in which neuraminidase treatment of breast tissue supernatant fluids led to decreased amounts of the most acidic isoform with a concomitant increase in the more neutral isoforms. The apparent increased relative amounts of the most acidic cathepsin D isoform in malignant breast tissue, coupled with the neuraminidase treatment results, provide further evidence that malignant breast tissue cathepsin D is abnormally glycosylated.

Benign breast disease as a breast cancer risk in Japanese women.

A hospital‐based retrospective cohort study of benign breast disease (BBD) as a risk factor of future breast cancer (BC) development was conducted. Four hundred and twenty‐eight patients with biopsied BBD were followed‐up for a median period of 8 years, together with age‐matched women with normal breasts (normal control) and BC patients (cancer control), at the ratio of 1:2:2. Twenty‐one breast cancers developed, 7 in the cases, 4 in the normal controls, and 10 in the BC controls, showing the relative risk (RR) with 95% confidence intervals (CD to be 3.5 (1.03–11.9) in the cases with respect to the normal controls. The RR of the cases is not lower than that of contralateral breast cancer incidence. There were no significant differences in the risks of cancers in other organs among the groups. Pathological examination revealed that only atypical hyperplasia increased the RR of BC, as compared with the normal control breast group, or with non‐proliferative disease. These results suggest that in a low‐risk country, Japan, BBD is a definite risk factor for BC development as in high‐risk countries.