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Loss of periostin/OSF-2 in ErbB2/Neu-driven tumors results in androgen receptor-positive molecular apocrine-like tumors with reduced Notch1 activity.

Sriram R, Lo V, Pryce B, Antonova L, Mears AJ, Daneshmand M, McKay B, Conway SJ, Muller WJ, Sabourin LA - Breast Cancer Res. (2015)

Bottom Line: Interestingly, Postn is frequently overexpressed in numerous human cancers, including breast, lung, colon, pancreatic, and ovarian cancer.Although Postn is exclusively expressed in the stromal fibroblasts of the mammary gland, Postn deletion does not affect mammary gland outgrowth during development or pregnancy.This may have important implications for the treatment of breast cancers involving the therapeutic targeting of periostin or Notch signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada. roshankumar2733@yahoo.com.

ABSTRACT

Introduction: Periostin (Postn) is a secreted cell adhesion protein that activates signaling pathways to promote cancer cell survival, angiogenesis, invasion, and metastasis. Interestingly, Postn is frequently overexpressed in numerous human cancers, including breast, lung, colon, pancreatic, and ovarian cancer.

Methods: Using transgenic mice expressing the Neu oncogene in the mammary epithelium crossed into Postn-deficient animals, we have assessed the effect of Postn gene deletion on Neu-driven mammary tumorigenesis.

Results: Although Postn is exclusively expressed in the stromal fibroblasts of the mammary gland, Postn deletion does not affect mammary gland outgrowth during development or pregnancy. Furthermore, we find that loss of Postn in the mammary epithelium does not alter breast tumor initiation or growth in mouse mammary tumor virus (MMTV)-Neu expressing mice but results in an apocrine-like tumor phenotype. Surprisingly, we find that tumors derived from Postn- animals express low levels of Notch protein and Hey1 mRNA but increased expression of androgen receptor (AR) and AR target genes. We show that tumor cells derived from wild-type animals do not proliferate when transplanted in a Postn- environment but that this growth defect is rescued by the overexpression of active Notch or the AR target gene prolactin-induced protein (PIP/GCDFP-15).

Conclusions: Together our data suggest that loss of Postn in an ErbB2/Neu/HER2 overexpression model results in apocrine-like tumors that activate an AR-dependent pathway. This may have important implications for the treatment of breast cancers involving the therapeutic targeting of periostin or Notch signaling.

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Loss of Postn leads to increased AR levels and activity. (A) H&E staining of primary tumors derived from wildtype (A) and Postn- mic (B). Postn-deficient tumors displayed an apocrine-like morphology with granular eosinophilic cytoplasm and prominent nucleoli. (C-F) Immunohistochemical analysis of independent tumors from Postn- mice shows an increase in AR levels and nuclear localization (G). At least 1000 nuclei from 3 independent tumors were assessed for AR nuclear translocation. The average and S.E.M. is shown. *P <0.05. (H) Western blot analysis of Postn- tumors reveals that Notch downregulation results in AR upregulation. Note one tumor sample where low AR levels can be correlated to high levels of Notch.
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Fig5: Loss of Postn leads to increased AR levels and activity. (A) H&E staining of primary tumors derived from wildtype (A) and Postn- mic (B). Postn-deficient tumors displayed an apocrine-like morphology with granular eosinophilic cytoplasm and prominent nucleoli. (C-F) Immunohistochemical analysis of independent tumors from Postn- mice shows an increase in AR levels and nuclear localization (G). At least 1000 nuclei from 3 independent tumors were assessed for AR nuclear translocation. The average and S.E.M. is shown. *P <0.05. (H) Western blot analysis of Postn- tumors reveals that Notch downregulation results in AR upregulation. Note one tumor sample where low AR levels can be correlated to high levels of Notch.

Mentions: Although loss of Postn did not affect overall survival and tumor development, our results show that it impaired tumor growth at heterotopic sites. In addition, careful histological examination of these tumors revealed a molecular apocrine-like phenotype, characterized by abundant granular eosinophilic cytoplasm, vesicular nuclei with prominent nucleoli (Figure 5A,B). The molecular apocrine phenotype is a characteristic of androgen receptor (AR)-positive breast cancers [59,60]. Therefore, we assessed AR protein levels in wild-type and Postn- NeuNDL tumors by Western blot analysis. Although AR mRNA levels were unchanged (not shown), AR protein levels were found to be upregulated 2-fold in the majority of tumors derived from Postn- mice (Figure 5H). Furthermore, immunohistochemical analysis for AR expression revealed a significant increase in nuclear localization of AR in tumors from Postn- animals, suggesting an increase in AR activity (Figure 5C-G). The increase in AR protein levels in Postn- tumors suggests a posttranscriptional upregulation or stabilization of AR protein levels [61,62]. Interestingly, we have identified one tumor sample where AR levels were unchanged which could be correlated with wild-type levels of active and total Notch. Together these findings demonstrate that the loss of Postn results in Notch downregulation which is accompanied by AR upregulation in the primary tumors. Furthermore, this suggests that the loss of Postn in ErbB2-expressing tumors confers an AR+ apocrine-like phenotype.Figure 5


Loss of periostin/OSF-2 in ErbB2/Neu-driven tumors results in androgen receptor-positive molecular apocrine-like tumors with reduced Notch1 activity.

Sriram R, Lo V, Pryce B, Antonova L, Mears AJ, Daneshmand M, McKay B, Conway SJ, Muller WJ, Sabourin LA - Breast Cancer Res. (2015)

Loss of Postn leads to increased AR levels and activity. (A) H&E staining of primary tumors derived from wildtype (A) and Postn- mic (B). Postn-deficient tumors displayed an apocrine-like morphology with granular eosinophilic cytoplasm and prominent nucleoli. (C-F) Immunohistochemical analysis of independent tumors from Postn- mice shows an increase in AR levels and nuclear localization (G). At least 1000 nuclei from 3 independent tumors were assessed for AR nuclear translocation. The average and S.E.M. is shown. *P <0.05. (H) Western blot analysis of Postn- tumors reveals that Notch downregulation results in AR upregulation. Note one tumor sample where low AR levels can be correlated to high levels of Notch.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4355979&req=5

Fig5: Loss of Postn leads to increased AR levels and activity. (A) H&E staining of primary tumors derived from wildtype (A) and Postn- mic (B). Postn-deficient tumors displayed an apocrine-like morphology with granular eosinophilic cytoplasm and prominent nucleoli. (C-F) Immunohistochemical analysis of independent tumors from Postn- mice shows an increase in AR levels and nuclear localization (G). At least 1000 nuclei from 3 independent tumors were assessed for AR nuclear translocation. The average and S.E.M. is shown. *P <0.05. (H) Western blot analysis of Postn- tumors reveals that Notch downregulation results in AR upregulation. Note one tumor sample where low AR levels can be correlated to high levels of Notch.
Mentions: Although loss of Postn did not affect overall survival and tumor development, our results show that it impaired tumor growth at heterotopic sites. In addition, careful histological examination of these tumors revealed a molecular apocrine-like phenotype, characterized by abundant granular eosinophilic cytoplasm, vesicular nuclei with prominent nucleoli (Figure 5A,B). The molecular apocrine phenotype is a characteristic of androgen receptor (AR)-positive breast cancers [59,60]. Therefore, we assessed AR protein levels in wild-type and Postn- NeuNDL tumors by Western blot analysis. Although AR mRNA levels were unchanged (not shown), AR protein levels were found to be upregulated 2-fold in the majority of tumors derived from Postn- mice (Figure 5H). Furthermore, immunohistochemical analysis for AR expression revealed a significant increase in nuclear localization of AR in tumors from Postn- animals, suggesting an increase in AR activity (Figure 5C-G). The increase in AR protein levels in Postn- tumors suggests a posttranscriptional upregulation or stabilization of AR protein levels [61,62]. Interestingly, we have identified one tumor sample where AR levels were unchanged which could be correlated with wild-type levels of active and total Notch. Together these findings demonstrate that the loss of Postn results in Notch downregulation which is accompanied by AR upregulation in the primary tumors. Furthermore, this suggests that the loss of Postn in ErbB2-expressing tumors confers an AR+ apocrine-like phenotype.Figure 5

Bottom Line: Interestingly, Postn is frequently overexpressed in numerous human cancers, including breast, lung, colon, pancreatic, and ovarian cancer.Although Postn is exclusively expressed in the stromal fibroblasts of the mammary gland, Postn deletion does not affect mammary gland outgrowth during development or pregnancy.This may have important implications for the treatment of breast cancers involving the therapeutic targeting of periostin or Notch signaling.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada. roshankumar2733@yahoo.com.

ABSTRACT

Introduction: Periostin (Postn) is a secreted cell adhesion protein that activates signaling pathways to promote cancer cell survival, angiogenesis, invasion, and metastasis. Interestingly, Postn is frequently overexpressed in numerous human cancers, including breast, lung, colon, pancreatic, and ovarian cancer.

Methods: Using transgenic mice expressing the Neu oncogene in the mammary epithelium crossed into Postn-deficient animals, we have assessed the effect of Postn gene deletion on Neu-driven mammary tumorigenesis.

Results: Although Postn is exclusively expressed in the stromal fibroblasts of the mammary gland, Postn deletion does not affect mammary gland outgrowth during development or pregnancy. Furthermore, we find that loss of Postn in the mammary epithelium does not alter breast tumor initiation or growth in mouse mammary tumor virus (MMTV)-Neu expressing mice but results in an apocrine-like tumor phenotype. Surprisingly, we find that tumors derived from Postn- animals express low levels of Notch protein and Hey1 mRNA but increased expression of androgen receptor (AR) and AR target genes. We show that tumor cells derived from wild-type animals do not proliferate when transplanted in a Postn- environment but that this growth defect is rescued by the overexpression of active Notch or the AR target gene prolactin-induced protein (PIP/GCDFP-15).

Conclusions: Together our data suggest that loss of Postn in an ErbB2/Neu/HER2 overexpression model results in apocrine-like tumors that activate an AR-dependent pathway. This may have important implications for the treatment of breast cancers involving the therapeutic targeting of periostin or Notch signaling.

Show MeSH
Related in: MedlinePlus