TLR4 activation by lipopolysaccharide confers survival advantage to growth factor deprived prostate cancer cells

Sumeet Jain, Sujit Suklabaidya, Biswajit Das, Sunil K. Raghav, Surinder Kumar Batra, Shantibhusan Senapati

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

BACKGROUND. Prostate cancer (PCa) cells express Toll-like receptor-4 (TLR4), a known pro-tumorigenic molecule for different cancer cells. The cancer cells residing in the avascular region of the tumor confront various metabolic stresses and continuously adapt mechanisms to overcome them. We hypothesized that TLR4 activation might provide direct survival advantage to metabolically stressed PCa cells. METHODS. We first investigated the effect of LPS on survival of serum deprived PCa cells. To understand the molecular mechanisms involved in TLR4 mediated PCa survival, we next investigated change in expression of markers for apoptosis, senescence and autophagy. Ultimately, the effect of LPS on established prostate tumors was confirmed in vivo using a syngeneic rat model for PCa. RESULTS. Lipopolysaccharide (LPS)-mediated TLR4 activation significantly enhanced survival of serum deprived (SD) PC3, DU145 and MAT-LyLu PCa cells. TLR4 inhibition by a specific inhibitor resulted in rapid death of SD-PC3 cells, which was significantly suppressed by LPS. Interestingly, LPS treatment suppressed macroautophagy in SD-PC3 cells and increased expression of CCL2 (C-C motif ligand-2), a known autophagy inhibitor and pro-survival factor. Intra-tumor LPS injection resulted in increased tumor mass, induced TLR4 activation, suppressed autophagy, and increased the macrophage population in MAT-LyLu-tumors. CONCLUSIONS. Our study reveals that bacterial LPS enhance survival of PCa cells under conditions of nutrient stress through TLR4 activation. Moreover, LPS induces overexpression of CCL2 involved in the suppression of starvation-induced macroautophagy in PCa cells, and enhanced macrophage population in prostate tumors in vivo. Taken together, the current study suggests the importance of bacterial infection or TLR4-activation in prostate cancer pathogenesis.

Original languageEnglish (US)
Pages (from-to)1020-1033
Number of pages14
JournalProstate
Volume75
Issue number10
DOIs
StatePublished - Jul 1 2015

Fingerprint

Toll-Like Receptor 4
Lipopolysaccharides
Prostatic Neoplasms
Intercellular Signaling Peptides and Proteins
Autophagy
Neoplasms
Serum
Prostate
Macrophages
Ligands
Physiological Stress
Starvation
Bacterial Infections
Population
Apoptosis
Food

Keywords

  • autophagy
  • CCL2
  • infection
  • lipopolysaccharide
  • LPS
  • metabolic stress
  • prostate cancer
  • TLR4

ASJC Scopus subject areas

  • Urology
  • Oncology

Cite this

TLR4 activation by lipopolysaccharide confers survival advantage to growth factor deprived prostate cancer cells. / Jain, Sumeet; Suklabaidya, Sujit; Das, Biswajit; Raghav, Sunil K.; Batra, Surinder Kumar; Senapati, Shantibhusan.

In: Prostate, Vol. 75, No. 10, 01.07.2015, p. 1020-1033.

Research output: Contribution to journalArticle

Jain, Sumeet ; Suklabaidya, Sujit ; Das, Biswajit ; Raghav, Sunil K. ; Batra, Surinder Kumar ; Senapati, Shantibhusan. / TLR4 activation by lipopolysaccharide confers survival advantage to growth factor deprived prostate cancer cells. In: Prostate. 2015 ; Vol. 75, No. 10. pp. 1020-1033.
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AU - Jain, Sumeet

AU - Suklabaidya, Sujit

AU - Das, Biswajit

AU - Raghav, Sunil K.

AU - Batra, Surinder Kumar

AU - Senapati, Shantibhusan

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N2 - BACKGROUND. Prostate cancer (PCa) cells express Toll-like receptor-4 (TLR4), a known pro-tumorigenic molecule for different cancer cells. The cancer cells residing in the avascular region of the tumor confront various metabolic stresses and continuously adapt mechanisms to overcome them. We hypothesized that TLR4 activation might provide direct survival advantage to metabolically stressed PCa cells. METHODS. We first investigated the effect of LPS on survival of serum deprived PCa cells. To understand the molecular mechanisms involved in TLR4 mediated PCa survival, we next investigated change in expression of markers for apoptosis, senescence and autophagy. Ultimately, the effect of LPS on established prostate tumors was confirmed in vivo using a syngeneic rat model for PCa. RESULTS. Lipopolysaccharide (LPS)-mediated TLR4 activation significantly enhanced survival of serum deprived (SD) PC3, DU145 and MAT-LyLu PCa cells. TLR4 inhibition by a specific inhibitor resulted in rapid death of SD-PC3 cells, which was significantly suppressed by LPS. Interestingly, LPS treatment suppressed macroautophagy in SD-PC3 cells and increased expression of CCL2 (C-C motif ligand-2), a known autophagy inhibitor and pro-survival factor. Intra-tumor LPS injection resulted in increased tumor mass, induced TLR4 activation, suppressed autophagy, and increased the macrophage population in MAT-LyLu-tumors. CONCLUSIONS. Our study reveals that bacterial LPS enhance survival of PCa cells under conditions of nutrient stress through TLR4 activation. Moreover, LPS induces overexpression of CCL2 involved in the suppression of starvation-induced macroautophagy in PCa cells, and enhanced macrophage population in prostate tumors in vivo. Taken together, the current study suggests the importance of bacterial infection or TLR4-activation in prostate cancer pathogenesis.

AB - BACKGROUND. Prostate cancer (PCa) cells express Toll-like receptor-4 (TLR4), a known pro-tumorigenic molecule for different cancer cells. The cancer cells residing in the avascular region of the tumor confront various metabolic stresses and continuously adapt mechanisms to overcome them. We hypothesized that TLR4 activation might provide direct survival advantage to metabolically stressed PCa cells. METHODS. We first investigated the effect of LPS on survival of serum deprived PCa cells. To understand the molecular mechanisms involved in TLR4 mediated PCa survival, we next investigated change in expression of markers for apoptosis, senescence and autophagy. Ultimately, the effect of LPS on established prostate tumors was confirmed in vivo using a syngeneic rat model for PCa. RESULTS. Lipopolysaccharide (LPS)-mediated TLR4 activation significantly enhanced survival of serum deprived (SD) PC3, DU145 and MAT-LyLu PCa cells. TLR4 inhibition by a specific inhibitor resulted in rapid death of SD-PC3 cells, which was significantly suppressed by LPS. Interestingly, LPS treatment suppressed macroautophagy in SD-PC3 cells and increased expression of CCL2 (C-C motif ligand-2), a known autophagy inhibitor and pro-survival factor. Intra-tumor LPS injection resulted in increased tumor mass, induced TLR4 activation, suppressed autophagy, and increased the macrophage population in MAT-LyLu-tumors. CONCLUSIONS. Our study reveals that bacterial LPS enhance survival of PCa cells under conditions of nutrient stress through TLR4 activation. Moreover, LPS induces overexpression of CCL2 involved in the suppression of starvation-induced macroautophagy in PCa cells, and enhanced macrophage population in prostate tumors in vivo. Taken together, the current study suggests the importance of bacterial infection or TLR4-activation in prostate cancer pathogenesis.

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KW - infection

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KW - LPS

KW - metabolic stress

KW - prostate cancer

KW - TLR4

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