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Oncolytic targeting of androgen-sensitive prostate tumor by the respiratory syncytial virus (RSV): consequences of deficient interferon-dependent antiviral defense.

Echchgadda I, Chang TH, Sabbah A, Bakri I, Ikeno Y, Hubbard GB, Chatterjee B, Bose S - BMC Cancer (2011)

Bottom Line: LNCaP cells failed to activate the type-I interferon (IFNα/β)-induced transcription factor STAT-1, which is required for antiviral gene expression, although these cells could produce IFN in response to RSV infection.We demonstrated that RSV is potentially a useful therapeutic tool in the treatment of androgen-sensitive and androgen-independent prostate cancer.Moreover, impaired IFN-mediated antiviral response is the likely cause of higher viral burden and resulting oncolysis of androgen-sensitive prostate cancer cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC-7758, San Antonio, TX 78229, USA.

ABSTRACT

Background: Oncolytic virotherapy for cancer treatment utilizes viruses for selective infection and death of cancer cells without any adverse effect on normal cells. We previously reported that the human respiratory syncytial virus (RSV) is a novel oncolytic virus against androgen-independent PC-3 human prostate cancer cells. The present study extends the result to androgen-dependent prostate cancer, and explores the underlying mechanism that triggers RSV-induced oncolysis of prostate cancer cells.

Methods: The oncolytic effect of RSV on androgen-sensitive LNCaP human prostate cancer cells and on androgen-independent RM1 murine prostate cancer cells was studied in vitro in culture and in vivo in a xenograft or allograft tumor model. In vitro, cell viability, infectivity and apoptosis were monitored by MTT assay, viral plaque assay and annexin V staining, respectively. In vivo studies involved virus administration to prostate tumors grown in immune compromised nude mice and in syngeneic immune competent C57BL/6J mice. Anti-tumorogenic oncolytic activity was monitored by measuring tumor volume, imaging bioluminescent tumors in live animals and performing histopathological analysis and TUNEL assay with tumors

Results: We show that RSV imposes a potent oncolytic effect on LNCaP prostate cancer cells. RSV infectivity was markedly higher in LNCaP cells compared to the non-tumorigenic RWPE-1 human prostate cells. The enhanced viral burden led to LNCaP cell apoptosis and growth inhibition of LNCaP xenograft tumors in nude mice. A functional host immune response did not interfere with RSV-induced oncolysis, since growth of xenograft tumors in syngeneic C57BL/6J mice from murine RM1 cells was inhibited upon RSV administration. LNCaP cells failed to activate the type-I interferon (IFNα/β)-induced transcription factor STAT-1, which is required for antiviral gene expression, although these cells could produce IFN in response to RSV infection. The essential role of IFN in restricting infection was further borne out by our finding that neutralizing IFN activity resulted in enhanced RSV infection in non-tumorigenic RWPE-1 prostate cells.

Conclusions: We demonstrated that RSV is potentially a useful therapeutic tool in the treatment of androgen-sensitive and androgen-independent prostate cancer. Moreover, impaired IFN-mediated antiviral response is the likely cause of higher viral burden and resulting oncolysis of androgen-sensitive prostate cancer cells.

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Interferon response is essential for limiting RSV infection in prostate cells. (a) RSV infection of RWPE-1 in the absence (untreated, UT) or in the presence of either control (Con Ab) or IFN neutralizing (IFN Ab) antibody. Infection was measured by plaque assay at 36 h post-infection. Plaque assay values expressed as pfu/ml represent mean ± standard deviation for three independent determinations. Standard deviations are shown by error bars. (b) Plaque assay showing RSV infectivity in Con Ab or IFN Ab treated cells. Culture supernatant from RSV infected RWPE-1 cells (+/- Con Ab or IFN Ab) was added to CV-1 cells at a dilution of 1 × 106. Plaques were observed on methyl-cellulose after crystal-violet staining.
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Figure 9: Interferon response is essential for limiting RSV infection in prostate cells. (a) RSV infection of RWPE-1 in the absence (untreated, UT) or in the presence of either control (Con Ab) or IFN neutralizing (IFN Ab) antibody. Infection was measured by plaque assay at 36 h post-infection. Plaque assay values expressed as pfu/ml represent mean ± standard deviation for three independent determinations. Standard deviations are shown by error bars. (b) Plaque assay showing RSV infectivity in Con Ab or IFN Ab treated cells. Culture supernatant from RSV infected RWPE-1 cells (+/- Con Ab or IFN Ab) was added to CV-1 cells at a dilution of 1 × 106. Plaques were observed on methyl-cellulose after crystal-violet staining.

Mentions: Deregulation of IFN-mediated antiviral response could occur due to either insufficient IFN production from cancer cells, or a dysfunctional IFN-activated JAK/STAT antiviral pathway. RSV-infected LNCaP cells produced high levels of IFN - even more than RWPE-1 cells (Figure 8a). However, the antiviral activity of IFN (as measured from the viral titer of the RSV-infected cells) was at least 100-fold higher in the case of RWPE-1 and PC-3 compared to LNCaP cells (Figure 8b). For these experiments (Figure 8b), cells were pre-treated with IFN for 16 h, followed by RSV infection in the continued presence of IFN. The viral titer was measured by performing plaque assay of medium supernatants. Representative plaque assay shows that IFN treatment caused drastic reduction of RSV infectivity in RWPE-1 (12 h and 24 h post-infection), while failing to significantly inhibit RSV infectivity/replication in LNCaP cells at 12 h and 24 h post-infection (Figure 8c). In contrast to LNCaP cells, PC-3 cells were protected against RSV to the antiviral action of IFN, since IFN treatment of PC-3 cells drastically inhibited virus replication (Figure 8d). In the absence of protection from IFN, RSV has selective growth advantage in LNCaP cells over RWPE-1 cells and PC-3 cells. Indeed, the IFN neutralizing antibody, which inhibited IFN-α/β mediated antiviral activity in RWPE-1 cells, caused significant elevation of the RSV titer in RWPE-1 cells (by approximately 15 fold), representing enhancement of viral infectivity by 750% (Figure 9a). A representative result from plaque assay of RSV-infected RWPE-1 cells that were pretreated with either control antibody or IFN-neutralizing antibody shows elevated viral titer in cells devoid of IFN response (Figure 9b). Results from Figure 9 demonstrate that IFN plays an important role in limiting RSV infection in RWPE-1 and PC-3 cells, whereas lack of this restriction in LNCaP cells associated with excessive viral replication and oncolysis.


Oncolytic targeting of androgen-sensitive prostate tumor by the respiratory syncytial virus (RSV): consequences of deficient interferon-dependent antiviral defense.

Echchgadda I, Chang TH, Sabbah A, Bakri I, Ikeno Y, Hubbard GB, Chatterjee B, Bose S - BMC Cancer (2011)

Interferon response is essential for limiting RSV infection in prostate cells. (a) RSV infection of RWPE-1 in the absence (untreated, UT) or in the presence of either control (Con Ab) or IFN neutralizing (IFN Ab) antibody. Infection was measured by plaque assay at 36 h post-infection. Plaque assay values expressed as pfu/ml represent mean ± standard deviation for three independent determinations. Standard deviations are shown by error bars. (b) Plaque assay showing RSV infectivity in Con Ab or IFN Ab treated cells. Culture supernatant from RSV infected RWPE-1 cells (+/- Con Ab or IFN Ab) was added to CV-1 cells at a dilution of 1 × 106. Plaques were observed on methyl-cellulose after crystal-violet staining.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3038980&req=5

Figure 9: Interferon response is essential for limiting RSV infection in prostate cells. (a) RSV infection of RWPE-1 in the absence (untreated, UT) or in the presence of either control (Con Ab) or IFN neutralizing (IFN Ab) antibody. Infection was measured by plaque assay at 36 h post-infection. Plaque assay values expressed as pfu/ml represent mean ± standard deviation for three independent determinations. Standard deviations are shown by error bars. (b) Plaque assay showing RSV infectivity in Con Ab or IFN Ab treated cells. Culture supernatant from RSV infected RWPE-1 cells (+/- Con Ab or IFN Ab) was added to CV-1 cells at a dilution of 1 × 106. Plaques were observed on methyl-cellulose after crystal-violet staining.
Mentions: Deregulation of IFN-mediated antiviral response could occur due to either insufficient IFN production from cancer cells, or a dysfunctional IFN-activated JAK/STAT antiviral pathway. RSV-infected LNCaP cells produced high levels of IFN - even more than RWPE-1 cells (Figure 8a). However, the antiviral activity of IFN (as measured from the viral titer of the RSV-infected cells) was at least 100-fold higher in the case of RWPE-1 and PC-3 compared to LNCaP cells (Figure 8b). For these experiments (Figure 8b), cells were pre-treated with IFN for 16 h, followed by RSV infection in the continued presence of IFN. The viral titer was measured by performing plaque assay of medium supernatants. Representative plaque assay shows that IFN treatment caused drastic reduction of RSV infectivity in RWPE-1 (12 h and 24 h post-infection), while failing to significantly inhibit RSV infectivity/replication in LNCaP cells at 12 h and 24 h post-infection (Figure 8c). In contrast to LNCaP cells, PC-3 cells were protected against RSV to the antiviral action of IFN, since IFN treatment of PC-3 cells drastically inhibited virus replication (Figure 8d). In the absence of protection from IFN, RSV has selective growth advantage in LNCaP cells over RWPE-1 cells and PC-3 cells. Indeed, the IFN neutralizing antibody, which inhibited IFN-α/β mediated antiviral activity in RWPE-1 cells, caused significant elevation of the RSV titer in RWPE-1 cells (by approximately 15 fold), representing enhancement of viral infectivity by 750% (Figure 9a). A representative result from plaque assay of RSV-infected RWPE-1 cells that were pretreated with either control antibody or IFN-neutralizing antibody shows elevated viral titer in cells devoid of IFN response (Figure 9b). Results from Figure 9 demonstrate that IFN plays an important role in limiting RSV infection in RWPE-1 and PC-3 cells, whereas lack of this restriction in LNCaP cells associated with excessive viral replication and oncolysis.

Bottom Line: LNCaP cells failed to activate the type-I interferon (IFNα/β)-induced transcription factor STAT-1, which is required for antiviral gene expression, although these cells could produce IFN in response to RSV infection.We demonstrated that RSV is potentially a useful therapeutic tool in the treatment of androgen-sensitive and androgen-independent prostate cancer.Moreover, impaired IFN-mediated antiviral response is the likely cause of higher viral burden and resulting oncolysis of androgen-sensitive prostate cancer cells.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, MC-7758, San Antonio, TX 78229, USA.

ABSTRACT

Background: Oncolytic virotherapy for cancer treatment utilizes viruses for selective infection and death of cancer cells without any adverse effect on normal cells. We previously reported that the human respiratory syncytial virus (RSV) is a novel oncolytic virus against androgen-independent PC-3 human prostate cancer cells. The present study extends the result to androgen-dependent prostate cancer, and explores the underlying mechanism that triggers RSV-induced oncolysis of prostate cancer cells.

Methods: The oncolytic effect of RSV on androgen-sensitive LNCaP human prostate cancer cells and on androgen-independent RM1 murine prostate cancer cells was studied in vitro in culture and in vivo in a xenograft or allograft tumor model. In vitro, cell viability, infectivity and apoptosis were monitored by MTT assay, viral plaque assay and annexin V staining, respectively. In vivo studies involved virus administration to prostate tumors grown in immune compromised nude mice and in syngeneic immune competent C57BL/6J mice. Anti-tumorogenic oncolytic activity was monitored by measuring tumor volume, imaging bioluminescent tumors in live animals and performing histopathological analysis and TUNEL assay with tumors

Results: We show that RSV imposes a potent oncolytic effect on LNCaP prostate cancer cells. RSV infectivity was markedly higher in LNCaP cells compared to the non-tumorigenic RWPE-1 human prostate cells. The enhanced viral burden led to LNCaP cell apoptosis and growth inhibition of LNCaP xenograft tumors in nude mice. A functional host immune response did not interfere with RSV-induced oncolysis, since growth of xenograft tumors in syngeneic C57BL/6J mice from murine RM1 cells was inhibited upon RSV administration. LNCaP cells failed to activate the type-I interferon (IFNα/β)-induced transcription factor STAT-1, which is required for antiviral gene expression, although these cells could produce IFN in response to RSV infection. The essential role of IFN in restricting infection was further borne out by our finding that neutralizing IFN activity resulted in enhanced RSV infection in non-tumorigenic RWPE-1 prostate cells.

Conclusions: We demonstrated that RSV is potentially a useful therapeutic tool in the treatment of androgen-sensitive and androgen-independent prostate cancer. Moreover, impaired IFN-mediated antiviral response is the likely cause of higher viral burden and resulting oncolysis of androgen-sensitive prostate cancer cells.

Show MeSH
Related in: MedlinePlus