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Bone marrow stromal antigen 2 expressed in cancer cells promotes mammary tumor growth and metastasis.

Mahauad-Fernandez WD, DeMali KA, Olivier AK, Okeoma CM - Breast Cancer Res. (2014)

Bottom Line: In vivo, we examined the effect of knockdown of BST-2 in two different murine carcinoma cells on tumor growth, metastasis, and survival.In mice, orthotopic implantation of mammary tumor cells lacking BST-2 increased tumor latency, decreased primary tumor growth, reduced metastases to distal organs, and prolonged host survival.Furthermore, we found that the cellular basis for the role of BST-2 in promoting tumorigenesis include BST-2-directed enhancement in cancer cell adhesion, anchorage-independency, migration, and invasion.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA, 52242-1109, USA. wadiedaniel-mahauadfernandez@uiowa.edu.

ABSTRACT

Introduction: Several innate immunity genes are overexpressed in human cancers and their roles remain controversial. Bone marrow stromal antigen 2 (BST-2) is one such gene whose role in cancer is not clear. BST-2 is a unique innate immunity gene with both antiviral and pro-tumor functions and therefore can serve as a paradigm for understanding the roles of other innate immunity genes in cancers.

Methods: Meta-analysis of tumors from breast cancer patients obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets were evaluated for levels of BST-2 expression and for tumor aggressiveness. In vivo, we examined the effect of knockdown of BST-2 in two different murine carcinoma cells on tumor growth, metastasis, and survival. In vitro, we assessed the effect of carcinoma cell BST-2 knockdown and/or overexpression on adhesion, anchorage-independent growth, migration, and invasion.

Results: BST-2 in breast tumors and mammary cancer cells is a strong predictor of tumor size, tumor aggressiveness, and host survival. In humans, BST-2 mRNA is elevated in metastatic and invasive breast tumors. In mice, orthotopic implantation of mammary tumor cells lacking BST-2 increased tumor latency, decreased primary tumor growth, reduced metastases to distal organs, and prolonged host survival. Furthermore, we found that the cellular basis for the role of BST-2 in promoting tumorigenesis include BST-2-directed enhancement in cancer cell adhesion, anchorage-independency, migration, and invasion.

Conclusions: BST-2 contributes to the emergence of neoplasia and malignant progression of breast cancer. Thus, BST-2 may (1) serve as a biomarker for aggressive breast cancers, and (2) be a novel target for breast cancer therapeutics.

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Suppression of BST-2 expression in cancer cells results in anchorage-independency. (A and C) Quantification of the number of colonies formed in soft agar by BST-2-expressing shControl, BST-2-suppressed sh137 and sh413 murine cells, MCF-7 (positive control), HMLE and NMuMG cells following a 20-day transformation assay. The bar represents number of colonies per field (n = 5) for each cell type. Error bars correspond to standard deviations. Significance was taken at P <0.001**. (B and D) Representative images of crystal violet-stained colonies from a soft agar assay showing anchorage-independent growth of cancer cells. Clones were imaged at 4X. Experiments were repeated multiple times with similar results. ns = not significant.
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Fig6: Suppression of BST-2 expression in cancer cells results in anchorage-independency. (A and C) Quantification of the number of colonies formed in soft agar by BST-2-expressing shControl, BST-2-suppressed sh137 and sh413 murine cells, MCF-7 (positive control), HMLE and NMuMG cells following a 20-day transformation assay. The bar represents number of colonies per field (n = 5) for each cell type. Error bars correspond to standard deviations. Significance was taken at P <0.001**. (B and D) Representative images of crystal violet-stained colonies from a soft agar assay showing anchorage-independent growth of cancer cells. Clones were imaged at 4X. Experiments were repeated multiple times with similar results. ns = not significant.

Mentions: Adaptation to new environment is a hallmark of aggressive tumors. To survive, cancer cells are able to grow and expand in the absence of attachments by overcoming anoikis [35]. Because BST-2-expressing shControl cells metastasized more efficiently than BST-2-suppressed sh413 cells in vivo (Figure 3), we used a soft agar colony formation assay to examine the possibility that BST-2 is important for anchorage-independent growth of mammary cancer cells. As expected, we observed reduced colony numbers (Figure 6A) and colony size (Figure 6B) in mammary cancer cells with suppressed BST-2 (intermediate-sh137 and low-sh413) compared to cells expressing high BST-2 (shControl). MCF-7 cells, known to form colonies [36,37], were used as positive control (Figure 6C and D) while normal human (HMLE) and murine (NMuMG) mammary epithelial cells were used as negative controls (Figure 6C and D). Interestingly, overexpression of BST-2 in low BST-2-expressing MCF-7 cells (Figure S5A in Additional file 5) increased MCF-7 colony size relative to empty vector control (Figure S5B and S5C in Additional file 5). These data suggest that suppression of BST-2 expression may diminish in vivo tumorigenicity of otherwise highly tumorigenic cancer cells by reducing anchorage-independence of tumor cells, thus preventing expansion of tumor cells, invasion to adjacent tissues, and dissemination throughout the body.Figure 6


Bone marrow stromal antigen 2 expressed in cancer cells promotes mammary tumor growth and metastasis.

Mahauad-Fernandez WD, DeMali KA, Olivier AK, Okeoma CM - Breast Cancer Res. (2014)

Suppression of BST-2 expression in cancer cells results in anchorage-independency. (A and C) Quantification of the number of colonies formed in soft agar by BST-2-expressing shControl, BST-2-suppressed sh137 and sh413 murine cells, MCF-7 (positive control), HMLE and NMuMG cells following a 20-day transformation assay. The bar represents number of colonies per field (n = 5) for each cell type. Error bars correspond to standard deviations. Significance was taken at P <0.001**. (B and D) Representative images of crystal violet-stained colonies from a soft agar assay showing anchorage-independent growth of cancer cells. Clones were imaged at 4X. Experiments were repeated multiple times with similar results. ns = not significant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4308845&req=5

Fig6: Suppression of BST-2 expression in cancer cells results in anchorage-independency. (A and C) Quantification of the number of colonies formed in soft agar by BST-2-expressing shControl, BST-2-suppressed sh137 and sh413 murine cells, MCF-7 (positive control), HMLE and NMuMG cells following a 20-day transformation assay. The bar represents number of colonies per field (n = 5) for each cell type. Error bars correspond to standard deviations. Significance was taken at P <0.001**. (B and D) Representative images of crystal violet-stained colonies from a soft agar assay showing anchorage-independent growth of cancer cells. Clones were imaged at 4X. Experiments were repeated multiple times with similar results. ns = not significant.
Mentions: Adaptation to new environment is a hallmark of aggressive tumors. To survive, cancer cells are able to grow and expand in the absence of attachments by overcoming anoikis [35]. Because BST-2-expressing shControl cells metastasized more efficiently than BST-2-suppressed sh413 cells in vivo (Figure 3), we used a soft agar colony formation assay to examine the possibility that BST-2 is important for anchorage-independent growth of mammary cancer cells. As expected, we observed reduced colony numbers (Figure 6A) and colony size (Figure 6B) in mammary cancer cells with suppressed BST-2 (intermediate-sh137 and low-sh413) compared to cells expressing high BST-2 (shControl). MCF-7 cells, known to form colonies [36,37], were used as positive control (Figure 6C and D) while normal human (HMLE) and murine (NMuMG) mammary epithelial cells were used as negative controls (Figure 6C and D). Interestingly, overexpression of BST-2 in low BST-2-expressing MCF-7 cells (Figure S5A in Additional file 5) increased MCF-7 colony size relative to empty vector control (Figure S5B and S5C in Additional file 5). These data suggest that suppression of BST-2 expression may diminish in vivo tumorigenicity of otherwise highly tumorigenic cancer cells by reducing anchorage-independence of tumor cells, thus preventing expansion of tumor cells, invasion to adjacent tissues, and dissemination throughout the body.Figure 6

Bottom Line: In vivo, we examined the effect of knockdown of BST-2 in two different murine carcinoma cells on tumor growth, metastasis, and survival.In mice, orthotopic implantation of mammary tumor cells lacking BST-2 increased tumor latency, decreased primary tumor growth, reduced metastases to distal organs, and prolonged host survival.Furthermore, we found that the cellular basis for the role of BST-2 in promoting tumorigenesis include BST-2-directed enhancement in cancer cell adhesion, anchorage-independency, migration, and invasion.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Carver College of Medicine, University of Iowa, 51 Newton Road, Iowa City, IA, 52242-1109, USA. wadiedaniel-mahauadfernandez@uiowa.edu.

ABSTRACT

Introduction: Several innate immunity genes are overexpressed in human cancers and their roles remain controversial. Bone marrow stromal antigen 2 (BST-2) is one such gene whose role in cancer is not clear. BST-2 is a unique innate immunity gene with both antiviral and pro-tumor functions and therefore can serve as a paradigm for understanding the roles of other innate immunity genes in cancers.

Methods: Meta-analysis of tumors from breast cancer patients obtained from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) datasets were evaluated for levels of BST-2 expression and for tumor aggressiveness. In vivo, we examined the effect of knockdown of BST-2 in two different murine carcinoma cells on tumor growth, metastasis, and survival. In vitro, we assessed the effect of carcinoma cell BST-2 knockdown and/or overexpression on adhesion, anchorage-independent growth, migration, and invasion.

Results: BST-2 in breast tumors and mammary cancer cells is a strong predictor of tumor size, tumor aggressiveness, and host survival. In humans, BST-2 mRNA is elevated in metastatic and invasive breast tumors. In mice, orthotopic implantation of mammary tumor cells lacking BST-2 increased tumor latency, decreased primary tumor growth, reduced metastases to distal organs, and prolonged host survival. Furthermore, we found that the cellular basis for the role of BST-2 in promoting tumorigenesis include BST-2-directed enhancement in cancer cell adhesion, anchorage-independency, migration, and invasion.

Conclusions: BST-2 contributes to the emergence of neoplasia and malignant progression of breast cancer. Thus, BST-2 may (1) serve as a biomarker for aggressive breast cancers, and (2) be a novel target for breast cancer therapeutics.

Show MeSH
Related in: MedlinePlus