Soo-Rim Kim

High aldehyde dehydrogenase activity enhances stem cell features in breast cancer cells by activating hypoxia-inducible factor-2α

High aldehyde dehydrogenase (ALDH) activity has been recognized as a marker of cancer stem cells (CSCs) in breast cancer. In this study, we examined whether inhibition of ALDH activity suppresses stem-like cell properties in a 4T1 syngeneic mouse model of breast cancer. We found that ALDH-positive 4T1 cells showed stem cell-like properties in vitro and in vivo. Blockade of ALDH activity reduced the growth of CSCs in breast cancer cell lines. Treatment of mice with the ALDH inhibitor diethylaminobenzaldehyde (DEAB) significantly suppressed 4T1 cell metastasis to the lung. Recent evidence suggests that ALDH affects the response of stem cells to hypoxia; therefore, we examined a possible link between ALDH and hypoxia signaling in breast cancer. Hypoxia-inducible factor-2α (HIF-2α) was highly dysregulated in ALDH-positive 4T1 cells. We observed that ALDH was highly correlated with the HIF-2α expression in breast cancer cell lines and tissues. DEAB treatment of breast cancer cells reduced the expression of HIF-2α in vitro. In addition, reduction of HIF-2α expression suppressed in vitro self-renewal ability and in vivo tumor initiation in ALDH-positive 4T1 cells. Therefore, our findings may provide the evidence necessary for exploring a new strategy in the treatment of breast cancer.

Ras activation contributes to the maintenance and expansion of Sca-1pos cells in a mouse model of breast cancer

The cancer stem cell (CSC) hypothesis proposes that CSCs are the root of cancer and cause cancer metastasis and recurrence. In this study, we examined whether Ras signaling is associated with stemness of the CSCs population characterized by the stem cell antigen (Sca-1) phenotype in a 4T1 syngeneic mouse model of breast cancer. The Sca-1(pos) putative CSCs had high levels of activated Ras and phosphorylated MEK (p-MEK), compared with counterparts. The Ras farnesylation inhibitor (FTI-277) suppressed the maintenance and expansion of CSCs. Therefore, selective inhibition of Ras activation may be useful for stem-specific cancer therapy.

Dysadherin can enhance tumorigenesis by conferring properties of stem-like cells to hepatocellular carcinoma cells

BACKGROUND & AIMS Hepatocellular carcinoma (HCC) is associated with a high potential for metastasis and disease recurrence, even after surgical resection. The cancer stem cell (CSC) hypothesis proposes that CSCs are responsible for chemo-resistance, recurrence, and metastasis. Dysadherin is a prognostic indicator of metastasis and poor survival in many different cancer types. In this study, we investigated the possible link between dysadherin and CSC in HCC. METHODS We analyzed the functional implications of dysadherin on cancer stemness by modification of the dysadherin gene in HCC cell lines. RESULTS The transfection of dysadherin cDNA into the liver cancer cell line PLC/PRF/5 enhanced the properties of CSCs, including anti-apoptosis, their sphere-forming ability, side population phenotype, and tumor initiation ability in vivo. Furthermore, knockdown of dysadherin in the liver cancer cell line SK-Hep1 suppressed its stem cell-like properties. CONCLUSIONS These results show that dysadherin give rise to properties of CSC in HCC. Therefore, these findings suggest that dysadherin may be a potential molecular prognostic marker of HCC and may aid in the development of more effective therapies.

Inhibition of Wnt1 expression reduces the enrichment of cancer stem cells in a mouse model of breast cancer

Breast cancer is the leading cause of deaths from cancer in women. Cancer recurrence is the most common cause of mortality in breast cancer patients. The cancer stem cell (CSC) hypothesis proposes that CSCs are the center of cancer development and recurrence. Targeting CSCs, in combination with standard chemotherapy, may prevent cancer recurrence and improve long-term survival. Stem cells can be enriched in non-adherent sphere cultures. To identify molecular targets in breast CSCs, we evaluated the transcription levels of stem cell-related genes in 4T1 mouse mammary cancer cells grown as spheres or in a monolayer culture. The most differentially expressed gene was found to be wingless-type MMTV integration site family member 1 (Wnt1) in the 4T1 sphere culture. Functionally, knockdown of Wnt1 in breast cancer cell lines suppressed the in vitro properties of the stem-like cells, including their sphere-forming ability and ALDH activity, whereas the addition of recombinant Wnt1 to breast cancer cell lines enhanced the in vitro properties of these stem-like cells. In addition, knockdown of Wnt1 in 4T1 cells affected the properties of the stem-like cells in vivo, including their tumorigenic potential and tumor initiation ability. Collectively, these results suggest that Wnt1 expression may give rise to the properties of CSCs in breast tumors. Therefore, targeting Wnt1-associated signaling proteins may provide an effective therapeutic approach for the treatment of advanced breast cancer.

Dysadherin expression promotes the motility and survival of human breast cancer cells by AKT activation.

High dysadherin expression has been recognized as a biological predictor of metastasis and poor prognosis for many different cancer types; however, the molecular mechanisms of how dysadherin affects cancer progression are still poorly understood. In this study, we examined whether AKT signaling could link dysadherin expression with downstream events that promote the metastatic potential of human breast cancer cells. Immunohistochemical analysis of breast cancer tissues showed that dysadherin expression was highly associated with elevated expression of phospho‐AKT. The introduction of dysadherin cDNA into BT‐474, MCF‐7 and T‐47D breast cancer cell lines enhanced their levels of AKT phosphorylation, while knockdown of dysadherin in MDA‐MB‐231 and Hs578T breast cancer cell lines suppressed AKT phosphorylation. Treatment with the AKT inhibitor triciribine suppressed dysadherin‐mediated pro‐metastatic effects, including epithelial–mesenchymal transition, cell motility and drug resistance. These findings suggest that dysadherin might contribute to breast cancer progression through AKT activation. (Cancer Sci 2012; 103: 1280–1289)

Abstract 5201: Suppression of WNT1 expression inhibits the maintenance and expansion of cancer stem cells in a mouse model of breast cancer

Cancer relapse is the most common cause of mortality in breast cancer patients. The cancer stem cell (CSC) hypothesis proposes that CSCs are the root of cancer. CSC-targeted therapies may prevent cancer relapse and provide more effective treatment. It has been known that stem cells can be enriched in non-adherent sphere culture. To identify molecular targets in breast CSC, we compared transcription levels of stem cell-related genes between tumorspheres established from Balb/c mice-derived 4T1 mammary carcinoma and mammospheres from the mammary glands of Balb/c mice. The most differentially expressed gene was found to be Wingless-type MMTV integration site family, member 1 (WNT1). To determine whether WNT1 has any relevance in breast carcinoma, we analyzed the expression of WNT1 in the human matched normal breast and breast cancer samples. Immunofluorescent staining showed that WNT1 expression was elevated ∼17-63-fold in cancerous tissues compared with non-cancerous tissues from the same breast cancer patients. Functionally, knockdown of WNT1 in 4T1 cells reduced the Aldefluor pos cell compartment enriched in CSCs and suppressed the properties of CSCs, including anti-apoptosis, sphere-forming ability, and tumor initiation ability in vivo. Collectively, these results show that WNT1 expression gives rise to properties of CSC in breast cancer. Therefore, the targeting of WNT1-associated signaling may provide an effective therapeutic approach in the treatment of advanced breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5201. doi:1538-7445.AM2012-5201

Abstract 3360: Inhibition of ALDH activity prevents the maintenance and expansion of cancer stem cell-like population in a mouse model of breast cancer

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC The cancer stem cell (CSC) hypothesis proposes that CSCs are the root of cancer and cause cancer metastasis and recurrence. High activity of aldehyde dehydrogenase (ALDH) has been recognized as a marker for normal and malignant stem cells. It has been also known that ALDH activity is important for multiple biological activities including drug resistance, cell differentiation, and oxidative metabolism. In this study, we focused on the molecular mechanism of ALDH activity in CSC dynamics. To address the underlying mechanism, we have used the 4T1 mouse model of breast cancer. We found that ALDHpos cells showed a high increase of the stem cell-like properties, such as sphere forming ability, expression of stem markers, and tumor initiation ability in vivo, when compared with the counterparts. Blockade of ALDH activity suppressed these properties of CSC. Especially, the high activity of ALDH was shown to enhance CSC properties through up-regulating Oct-4 expression that is dependent on oxygen-related transcription factor. Therefore, these findings suggest that the selective targeting of ALDH activity may be useful for stem specific cancer therapies. 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 3360.

Abstract 4244: Dysadherin can enhance tumorigenesis through conferring properties of stem-like cells to hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is associated with a high potential for metastasis and disease recurrence, even after surgical resection. The cancer stem cell (CSC) hypothesis proposes that CSCs are responsible for chemo-resistance, recurrence and metastasis. Dysadherin is a prognostic indicator of metastasis and poor survival in many different cancer types. In this study, we investigated the possible link between dysadherin and CSC in HCC. The transfection of dysadherin cDNA into the liver cancer cell line PLC/PRF/5 enhanced the properties of CSC, including anti-apoptosis, sphere-forming ability, side population (SP) phenotype and tumor initiation ability in vivo. Furthermore, knockdown of dysadherin in the liver cancer cell line SK-Hep1 suppressed its stem cell-like properties. In particular, SP phenotype is mediated by the ATP-binding cassette (ABC) transporter proteins which are responsible for multidrug resistance (MDR) that is a major obstacle in cancer chemotherapy. Dysadherin was also shown to regulate ABCB1 expression. Taken together, these results show that new roles for the dysadherin in cancer progression that was in part dependent on CSC dynamics. Therefore, these findings suggest that dysadherin may be a potential molecular prognostic marker of HCC and may aid in the development of more effective therapies. 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 4244.

5-Aza-2`-deoxycytidine Inhibits the Maintenance of Cancer Stem Cell in a Mouse Model of Breast Cancer

Aberrant DNA methylation plays an important role in the development of cancer. It has been reported recently that DNA hypermethylation is involved in the maintenance of cancer stem cells. The present study was designed to test the hypothesis that the demethylating agent, 5-aza-2`-deoxycytidine (AZA), can inhibit the potential for maintenance of cancer stem cells. To validate this hypothesis, we used 4T1 syngeneic mouse models of breast cancer. The AZA pre-treated 4T1 cells showed a dramatic inhibition of tumorsphere formation, compared to their counterparts in vitro. In addition, the AZA treatment significantly suppressed the expression of stem regulator genes, such as oct-4, nanog and sox2, compared to counterparts in vivo. Therefore, selective inhibition of DNA methylation may be useful for stem-specific cancer therapy.