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Diverse effects of ANXA7 and p53 on LNCaP prostate cancer cells are associated with regulation of SGK1 transcription and phosphorylation of the SGK1 target FOXO3A.

Srivastava M, Leighton X, Starr J, Eidelman O, Pollard HB - Biomed Res Int (2014)

Bottom Line: In addition, p53 reduced the expression of aberrant SGK1 protein form in LNCaP.Using Ingenuity Pathway Analysis and p53-signature genes, we elucidated the role of distinct SGK1/FOXO3A-associated regulation in p53 versus ANXA7 responses and proposed that aberrant SGK1 could affect reciprocal SGK1-FOXO3A-Akt regulation.Thus, the failure of the cell growth regulator p53 versus the phospholipid-binding ANXA7 could be potentially attributed to its diverse effects on SGK1-FOXO3A-Akt pathway in the PTEN-deficient LNCaP.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Physiology and Genetics and Institute for Molecular Medicine, Uniformed Services University of Health Sciences (USUHS), School of Medicine, Bethesda, MD 20814, USA.

ABSTRACT
Tumor suppressor function of the calcium/phospholipid-binding Annexin-A7 (ANXA7) has been shown in Anxa7-deficient mice and validated in human cancers. In the androgen-resistant prostate cancer cells, ANXA7 and p53 showed similar cytotoxicity levels. However, in the androgen-sensitive LNCaP, ANXA7 greatly exceeded the p53-induced cytotoxicity. We hypothesized that the p53 underperformance in LNCaP could be due to the involvement of p53-responsive SGK1 and FOXO3A. In this study, we show that p53 failed to match programmed cell death (PCD) and G1-arrest that were induced by ANXA7 in LNCaP. WT-ANXA7 preserved total FOXO3A expression with no hyperphosphorylation that could enable FOXO3A nuclear translocation and proapoptotic transcription. In contrast, in the p53-transfected LNCaP cells with maintained cell proliferation, the phosphorylated (but not total) FOXO3A fraction was increased implying a predominantly cytoplasmic localization and, subsequently, a lack of FOXO3A proapoptotic transcription. In addition, p53 reduced the expression of aberrant SGK1 protein form in LNCaP. Using Ingenuity Pathway Analysis and p53-signature genes, we elucidated the role of distinct SGK1/FOXO3A-associated regulation in p53 versus ANXA7 responses and proposed that aberrant SGK1 could affect reciprocal SGK1-FOXO3A-Akt regulation. Thus, the failure of the cell growth regulator p53 versus the phospholipid-binding ANXA7 could be potentially attributed to its diverse effects on SGK1-FOXO3A-Akt pathway in the PTEN-deficient LNCaP.

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Aberrant SGK1 isoforms in LNCaP compared to DU145. (a) SGK1 cDNA from LNCaP and DU145 was sequenced and aligned with wild-type SGK1 reference. The alignment image shows the missing exon11 in LNCaP (red dotted line) and the G/C-change in DU145. (b) SGK1 isoform in LNCaP is designated by an arrow. Both cells are represented by controls only (parental and vector alone as 1 and 2, resp.).
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fig4: Aberrant SGK1 isoforms in LNCaP compared to DU145. (a) SGK1 cDNA from LNCaP and DU145 was sequenced and aligned with wild-type SGK1 reference. The alignment image shows the missing exon11 in LNCaP (red dotted line) and the G/C-change in DU145. (b) SGK1 isoform in LNCaP is designated by an arrow. Both cells are represented by controls only (parental and vector alone as 1 and 2, resp.).

Mentions: In order to further explore a possible role of aberrant SGK1 in FOXO3A hyperphosphorylation in LNCaP, we examined SGK1 cDNA in LNCaP versus DU145. Unlike DU145, LNCaP displayed a double-band for full-length SGK1 cDNA, thereby validating a slightly smaller size of the extra-SGK1-transcript (not shown). cDNA sequence analysis verified that the SGK1 sequences from LNCaP lacked the entire exon11 (90nt). In addition, SGK1 from DU145 had a G/C-change (∗) in the same exon as compared to wild-type SGK1 reference (Figure 4(a)). Distinct SGK1 protein expression profiles in parental LNCaP and DU145 maintained their cell specificity in the ANXA7- and p53-transfected cells. LNCaP possessed a smaller extra-LMW-SGK1 protein form (marked by an arrow, Figure 4(b)) that was not found in DU145 cells. Most remarkably, both ANXA7s enhanced, while p53 abolished, the extra-45kDa-SGK1. In addition, WT-ANXA7 particularly induced ∼15 kDa-SGK1 in LNCaP. In DU145, p53 reduced the LMW-SGK1-forms, while both ANXA7s did not cause detectable changes. These results suggest that the diverse LMW-SGK1 profiles in response to ANXA7 and p53 could distinctly affect the phosphorylation of SGK1-targets.


Diverse effects of ANXA7 and p53 on LNCaP prostate cancer cells are associated with regulation of SGK1 transcription and phosphorylation of the SGK1 target FOXO3A.

Srivastava M, Leighton X, Starr J, Eidelman O, Pollard HB - Biomed Res Int (2014)

Aberrant SGK1 isoforms in LNCaP compared to DU145. (a) SGK1 cDNA from LNCaP and DU145 was sequenced and aligned with wild-type SGK1 reference. The alignment image shows the missing exon11 in LNCaP (red dotted line) and the G/C-change in DU145. (b) SGK1 isoform in LNCaP is designated by an arrow. Both cells are represented by controls only (parental and vector alone as 1 and 2, resp.).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4016907&req=5

fig4: Aberrant SGK1 isoforms in LNCaP compared to DU145. (a) SGK1 cDNA from LNCaP and DU145 was sequenced and aligned with wild-type SGK1 reference. The alignment image shows the missing exon11 in LNCaP (red dotted line) and the G/C-change in DU145. (b) SGK1 isoform in LNCaP is designated by an arrow. Both cells are represented by controls only (parental and vector alone as 1 and 2, resp.).
Mentions: In order to further explore a possible role of aberrant SGK1 in FOXO3A hyperphosphorylation in LNCaP, we examined SGK1 cDNA in LNCaP versus DU145. Unlike DU145, LNCaP displayed a double-band for full-length SGK1 cDNA, thereby validating a slightly smaller size of the extra-SGK1-transcript (not shown). cDNA sequence analysis verified that the SGK1 sequences from LNCaP lacked the entire exon11 (90nt). In addition, SGK1 from DU145 had a G/C-change (∗) in the same exon as compared to wild-type SGK1 reference (Figure 4(a)). Distinct SGK1 protein expression profiles in parental LNCaP and DU145 maintained their cell specificity in the ANXA7- and p53-transfected cells. LNCaP possessed a smaller extra-LMW-SGK1 protein form (marked by an arrow, Figure 4(b)) that was not found in DU145 cells. Most remarkably, both ANXA7s enhanced, while p53 abolished, the extra-45kDa-SGK1. In addition, WT-ANXA7 particularly induced ∼15 kDa-SGK1 in LNCaP. In DU145, p53 reduced the LMW-SGK1-forms, while both ANXA7s did not cause detectable changes. These results suggest that the diverse LMW-SGK1 profiles in response to ANXA7 and p53 could distinctly affect the phosphorylation of SGK1-targets.

Bottom Line: In addition, p53 reduced the expression of aberrant SGK1 protein form in LNCaP.Using Ingenuity Pathway Analysis and p53-signature genes, we elucidated the role of distinct SGK1/FOXO3A-associated regulation in p53 versus ANXA7 responses and proposed that aberrant SGK1 could affect reciprocal SGK1-FOXO3A-Akt regulation.Thus, the failure of the cell growth regulator p53 versus the phospholipid-binding ANXA7 could be potentially attributed to its diverse effects on SGK1-FOXO3A-Akt pathway in the PTEN-deficient LNCaP.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Physiology and Genetics and Institute for Molecular Medicine, Uniformed Services University of Health Sciences (USUHS), School of Medicine, Bethesda, MD 20814, USA.

ABSTRACT
Tumor suppressor function of the calcium/phospholipid-binding Annexin-A7 (ANXA7) has been shown in Anxa7-deficient mice and validated in human cancers. In the androgen-resistant prostate cancer cells, ANXA7 and p53 showed similar cytotoxicity levels. However, in the androgen-sensitive LNCaP, ANXA7 greatly exceeded the p53-induced cytotoxicity. We hypothesized that the p53 underperformance in LNCaP could be due to the involvement of p53-responsive SGK1 and FOXO3A. In this study, we show that p53 failed to match programmed cell death (PCD) and G1-arrest that were induced by ANXA7 in LNCaP. WT-ANXA7 preserved total FOXO3A expression with no hyperphosphorylation that could enable FOXO3A nuclear translocation and proapoptotic transcription. In contrast, in the p53-transfected LNCaP cells with maintained cell proliferation, the phosphorylated (but not total) FOXO3A fraction was increased implying a predominantly cytoplasmic localization and, subsequently, a lack of FOXO3A proapoptotic transcription. In addition, p53 reduced the expression of aberrant SGK1 protein form in LNCaP. Using Ingenuity Pathway Analysis and p53-signature genes, we elucidated the role of distinct SGK1/FOXO3A-associated regulation in p53 versus ANXA7 responses and proposed that aberrant SGK1 could affect reciprocal SGK1-FOXO3A-Akt regulation. Thus, the failure of the cell growth regulator p53 versus the phospholipid-binding ANXA7 could be potentially attributed to its diverse effects on SGK1-FOXO3A-Akt pathway in the PTEN-deficient LNCaP.

Show MeSH
Related in: MedlinePlus