Akiko Sasaki

The β-catenin signaling pathway induces aggressive potential in breast cancer by up-regulating the chemokine CCL5

β-Catenin signaling plays a pivotal role in the genesis of a variety of malignant tumors, but its role in breast cancer has not been fully elucidated. Here, we examined whether deregulation of β-catenin signaling is related to the aggressive characteristics of certain types of breast cancers. Analysis of cytokine levels in MDA-MB-231 cells overexpressing a constitutively active form of β-catenin (CAβ-catenin) revealed a higher level of CCL5 expression. Cells transfected with CAβ-catenin or stimulated with recombinant CCL5 exhibited increased cell invasion activity and spheroid formation in vitro. Furthermore, CAβ-catenin-transfected MDA-MB-231 cells formed larger tumor masses that contained more Ki-67-positive cells and infiltrating lymphocytes than did the control cells. An inhibitor of CCR5 and a pan-CXCR neutralizing antibody dramatically reduced CAβ-catenin-promoted activities. In addition to CCL5, 6-BIO, a chemical activator of β-catenin, induced cell invasion and spheroid formation in MDA-MB-231 cells. Furthermore, high levels of nuclear β-catenin accumulation were detected in breast cancer in patients with metastasis but not in those without metastasis. Nuclear β-catenin localization is related to increased CCL5 production in breast cancer. These findings suggest that β-catenin expression enhances tumor progression via chemokine production in breast cancers and that β-catenin signaling is a critical regulator of the aggressive traits of breast cancers.

Characteristic Genes in Luminal Subtype Breast Tumors with CD44+CD24–/Low Gene Expression Signature

Objective: Breast cancer cells with CD44+CD24–/low gene expression signature have been suggested to have stem cell-like tumor-initiating properties. The purpose of this study is to clarify the gene expression profiling of cells with CD44+CD24–/low gene expression signature in the luminal subtype. Methods: Laser capture microdissection was used to select the isolation of cancer cells in 35 frozen tissues of breast cancer, and RNA extracted from these cells was examined by real-time RT-PCR to quantify CD44 and CD24 expressions. Human stem cell RT2 Profiler PCR Array was used for gene expression analysis in the groups of CD44+CD24–/low and CD44+CD24+ gene expression signature. Results: Thirty-five tumors were divided into 3 groups. Group A was composed of the CD44+CD24–/low type, in which the ratio of CD44/CD24 was >10.0. Group B was composed of the CD44+CD24+ type, in which the ratio was >0.1 and ≤10.0. In group C, composed of the CD44–/lowCD24+ type, the ratio was <0.1. The number of tumors in groups A, B, and C were 5, 28, and 2, respectively. Regarding the correlation of CD44/CD24 status with tumor characteristics, the tumors of group A were significantly associated with axillary lymph node metastasis compared with those of group B (p = 0.033). There were no significant differences in tumor size, nuclear grade, or HER2 status between the two groups. According to signaling pathways, the number of expression genes for the Notch pathway in group A was significantly greater than in group B (p = 0.028). Overexpressed genes for ALDH1 (p = 0.021) and SOX2 (p = 0.018) were noted in group A compared to group B. Conclusion: This study suggests that the Notch pathway may be an important signaling pathway in luminal subtype with CD44+CD24–/low gene expression signature. In addition, either ALDH1 or SOX2 may be a candidate marker for cancer stem cells in luminal subtype breast cancer.

Histopathological and physiological characteristics of cultured human ACTH-secreting cells derived from a rapidly growing pituitary adenoma.

We observed the histopathological and physiological characteristics of adrenocorticotropic hormone (ACTH)-secreting adenoma cells derived from a rapidly growing pituitary adenoma, which have firm cell attachment and well-preserved hormonal function in a relatively longterm culture. Corticotrophs, obtained from a 43-year-old woman with Cushings disease in whom plasma ACTH levels increased in response to 1-deamino-8-D-arginine vasopressin (DDAVP) stimulation and the proliferative potential was very high, were grown in tissue culture for up to 6 months. The morphological features were observed by phase contrast and electron microscopy. The cultured cells were incubated with corticotroph-releasing hormone (CRH), arginine vasopressin (AVP), or DDAVP, and ACTH in the medium was measured by radioimmunoassay (RIA). The morphology of the ACTH-secreting adenoma cells in culture revealed a mixed population of formed clusters and spindle-shaped fibroblast-like cells. The adenoma cells were immunohistochemically positive only for ACTH. On electron microscopic observation, pituitary tumor cells obtained 6 days after seeding demonstrated many secretory granules, well-developed rough endoplasmic reticulum, and mitochondria; fewer secretory granules were observed after cultivation for 24 days. ACTH levels in the incubation media were elevated with stimulation by DDAVP, AVP, or CRH. In this study, the establishment of relatively longterm culture of human pituitary adenoma cells seemed to be due to the high proliferative potential of this adenoma. This in vitro study may imply that DDAVP as well as AVP directly stimulates ACTH release from corticotropic adenoma cells.

Eribulin upregulates miR-195 expression and downregulates Wnt3a expression in non-basal-like type of triple-negative breast cancer cell MDA-MB-231.

Triple-negative breast cancer (TNBC), which does not show hormone sensitivity, is a poor prognosis disease without an established targeted treatment, so that establishing a therapeutic target for each subtype is desired. In addition, microRNA (miRNA), a non-cording RNA 19–25 nucleotide-longs in length, is known to be involved in regulating gene expression. We examined miRNA expression after exposure to eribulin, MDA-MB-231 cells, non-basal-like type of TNBC cell lines, and HCC1143 cells, basal-like type of TNBC cell lines. The activity of caspase-3 significantly increased compared to the control in MDA-MB-231, whereas no significant difference was observed in HCC1143. The expression level of 20-miRNAs significantly increased compared to the control in MDA-MB-231 after exposure to eribulin. The expression level of 6-miRNAs also significantly increased compared to the control in HCC1143. In these 2 cell types, miR-125b-1 and miR-195 were commonly expressed. While the expression level of miR-125b-1 decreased in both cells, the expression level of miR-195 increased in MDA-MB-231 and decreased in HCC1143. The expression level of miR-195 targeting Wnt3a significantly decreased compared to the control in MDA-MB-231, whereas it significantly increased in HCC1143. These results showed that exposure to eribulin highly increased the expression of miR-195 while it decreased the expression of Wnt3a in non-basal-like type of TNBC. Some miRNAs are known to regulate other signaling pathways involved in human pathogenesis by regulating the Wnt signaling pathway, and miRNA can act as a tumor-suppressing gene; therefore, miR-195 may serve as a therapeutic target in non-basal-like type of TNBC.

Abstract 4687: Gene expression of breast cancer with CD44+CD24-/low genotype

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Purpose: Breast cancer cells with a CD44+CD24-/low phenotype have been suggested to have tumor-initiating properties with stem cell-like. The purpose of this study is to clarify the gene expression profiling of cells with different CD44/CD24 genotypes within breast cancer. Methods: Laser-captured microdissection was used to select the isolation of cancer cells in 36 frozen tissues of breast cancer, and RNA extracted from these cells was examined by real-time RT-PCR to quantify CD44 and CD24 expressions. Human stem cell RT2 profiler PCR array was used for gene expression analysis in the groups of different CD44/CD24 genotype. Associations between different CD44/CD24 genotypes and clinical variables were assessed by Fishers exact test, and the Mann-Whitney U test was used for gene expression profiling. P<0.05 was considered significant. Results: Thirty-six tumors were divided into 3 groups. Group A was composed of CD44+CD24-/low genotype, in which the ratio of CD44/CD24 was >1.0. Group B was composed of CD44+CD24+ genotype, in which that was 0.1 < ratio ≤ 1.0. In group C of CD44-/lowCD24+ genotype, that was < 0.1. The number of tumors in group A, B and C was 5, 29 and 2, respectively. Regarding the correlation of CD44/CD24 status with tumor characteristics, tumors of group A were significantly associated with lymph node metastasis compared with those of group B (P=0.029). The number of tumor with HER 2 score 3 within group A and B was 0 and 11, respectively. There was no significantly difference in ER status and tumor size. As far as the signaling pathways, the number of expression genes for Notch pathway in group A was significantly greater than in group B (P=0.028), and that for Wnt pathway was not significantly different between group A and B. Overexpressed gene in group A was NUMB, which is related to the programmed cell death. MYST1 and SOX2 tended to show higher levels of group A than of group B. Conclusion: This study suggests that Notch pathway may be more important than Wnt pathway on breast cancer with CD44+CD24-/low genotype, and the CD44+CD24-/low status would be associated with low/negative HER2 expression. Moreover, the gene of self-renewal markers, such as MYST1, SOX2 and NUMB might be a target for therapy against breast cancer with low/negative HER2 expression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4687.

Cancer stem-like cells have cisplatin resistance and miR-93 regulate p21 expression in breast cancer

Aim: This study aims to examine the role of microRNAs (miRNAs) in regulating the expression of p21, a cyclin-dependent kinase inhibitor, and in inducing resistance to cisplatin, an anticancer drug. Methods: Human breast cancer cell line MDA-MB231 cells were separated into two subpopulations, cancer stem-like cells (CSCs) and cancer cells, based on the expression of cell surface antigens CD44 and CD24. Results: p21 protein expression was higher in CSCs than in cancer cells. Exposure of MDA-MB-231 cells to cisplatin increased p21 protein expression. However, p21 expression was significantly lower in cisplatin-treated CSCs than in cisplatin-treated cancer cells, suggesting that p21-dependent cell cycle suppression was lower in CSCs than in cancer cells. Moreover, caspase-3 activity was significantly lower in cisplatin-treated CSCs than in cisplatin-treated cancer cells, indicating that CSCs were more resistant to cisplatin-induced apoptosis than cancer cells. Treatment with miR-93 inhibitors increased p21 expression in CSCs, suggesting that miR-93 suppressed p21 expression. Conclusion: The results of the present study indicate that CSCs contribute to cisplatin resistance of MDA-MB231 cells and suggest that miR-93 inhibits the expression of p21, a factor involved in drug resistance.

Abstract 4666: Identification of cancer stem cell-like fractions in cultured oral squamous cell carcinoma and expression of keratin 15 as a putative cancer stem cell marker

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Although it is well known that one of the intermediate filament proteins cytokeratin 15 (CK15) can be a marker for not only epithelial stem cells but also cutaneous neoplasm and sebaceous tumors, the expression of CK15 in oral squamous cell carcinoma has not been reported. In this study, we investigated the expression of CK15 in different stages of epithelial dysplasia, carcinoma in situ (CIS) and squamous cell carcinoma (SCC) by immunohistochemical analysis and genetic analysis. Only basal cells in normal epithelia showed strong positive staining for CK15. Which was spread to basal cells and parabasal cells in epithelial dysplasia. In CIS and SCC, however, no reactivity was observed for CK15 except for the peripheral part of carcinoma nest in SCC. On the other hand, CK15 expression in chemoresistant SCC showed overall positive staining. In contrast to CK15 expression, transcription factor P63 which is known to putative keratinocyte stem cell marker showed different staining patterns from those of CK15. These observations seem to indicate that CK15 staining in combination with P63 could be a useful marker for pathologic diagnosis in terms of predicting malignant change and chemoresistance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4666.