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Modulators of arginine metabolism support cancer immunosurveillance.

Capuano G, Rigamonti N, Grioni M, Freschi M, Bellone M - BMC Immunol. (2009)

Bottom Line: Tumor-associated accrual of myeloid derived suppressor cells (MDSC) in the blood, lymphoid organs and tumor tissues may lead to perturbation of the arginine metabolism and impairment of the endogenous antitumor immunity.Treatment of tumor-bearing mice with either the phosphodiesterase-5 inhibitor sildenafil or the nitric-oxide synthase (NOS) inhibitor L-NAME significantly restrained tumor growth and expanded the tumor-specific immune response.Our data emphasize the role of MDSC in modulating the endogenous tumor-specific immune response and underline the anti-neoplastic therapeutic potential of arginine metabolism modulators.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cancer Immunotherapy and Gene Therapy Program, Istituto Scientifico San Raffaele, Via Olgettina 58, 20132, Milan, Italy. giusy_capuano@hotmail.com

ABSTRACT

Background: Tumor-associated accrual of myeloid derived suppressor cells (MDSC) in the blood, lymphoid organs and tumor tissues may lead to perturbation of the arginine metabolism and impairment of the endogenous antitumor immunity. The objective of this study was to evaluate whether accumulation of MDSC occurred in Th2 prone BALB/c and Th1 biased C57BL/6 mice bearing the C26GM colon carcinoma and RMA T lymphoma, respectively, and to investigate whether N(G) nitro-L-arginine methyl ester (L-NAME) and sildenafil, both modulators of the arginine metabolism, restored antitumor immunity.

Results: We report here that MDSC accumulate in the spleen and blood of mice irrespective of the mouse and tumor model used. Treatment of tumor-bearing mice with either the phosphodiesterase-5 inhibitor sildenafil or the nitric-oxide synthase (NOS) inhibitor L-NAME significantly restrained tumor growth and expanded the tumor-specific immune response.

Conclusion: Our data emphasize the role of MDSC in modulating the endogenous tumor-specific immune response and underline the anti-neoplastic therapeutic potential of arginine metabolism modulators.

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Modulators of arginine metabolism alter MDSC accumulation in the blood of tumor-bearing mice. BALB/c and C57BL/6 mice were challenged s.c. with C26GM and RMA cells, respectively. The same day, mice were randomly assigned to either one of the following treatments: L-NAME or sildenafil (given i.p. or dissolved in drinking water) or vehicle (PBS; V) i.p. (see Materials and Methods section for experimental details). Tumor-bearing BALB/c and C57BL/6 mice were killed 9 and 15 day later. Recruitment of CD11b+Gr1- and CD11b+Gr1+ cells in the spleen (A, C) and blood (B, D) of tumor-bearing BALB/c (A, B) and C57BL/6 mice (C, D) was investigated by flow cytometry. Histograms report the percentage of CD11b+ Gr1- and CD11b+ Gr1+ cells as aggregated data (average ± SD) for the experimental groups reported in the legend of Fig. 3. Alternatively, magnetic bead sorted CD11b+ cells from the spleen of RMA (E) tumor bearing mice were lysed and analyzed for relative Arg enzyme activity. Student's T test: ***p < 0.001, **0.001 < p < 0.05.
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Figure 5: Modulators of arginine metabolism alter MDSC accumulation in the blood of tumor-bearing mice. BALB/c and C57BL/6 mice were challenged s.c. with C26GM and RMA cells, respectively. The same day, mice were randomly assigned to either one of the following treatments: L-NAME or sildenafil (given i.p. or dissolved in drinking water) or vehicle (PBS; V) i.p. (see Materials and Methods section for experimental details). Tumor-bearing BALB/c and C57BL/6 mice were killed 9 and 15 day later. Recruitment of CD11b+Gr1- and CD11b+Gr1+ cells in the spleen (A, C) and blood (B, D) of tumor-bearing BALB/c (A, B) and C57BL/6 mice (C, D) was investigated by flow cytometry. Histograms report the percentage of CD11b+ Gr1- and CD11b+ Gr1+ cells as aggregated data (average ± SD) for the experimental groups reported in the legend of Fig. 3. Alternatively, magnetic bead sorted CD11b+ cells from the spleen of RMA (E) tumor bearing mice were lysed and analyzed for relative Arg enzyme activity. Student's T test: ***p < 0.001, **0.001 < p < 0.05.

Mentions: We investigated whether treatment with L-NAME or sildenafil modified accrual of MDSC in the spleen and blood of tumor-challenged mice. Flow cytometry analyses conducted ex vivo the day of mouse killing showed a clear accumulation of both CD11b+Gr1+ and CD11b+Gr1- cells in the spleen of BALB/c mice bearing C26GM tumors, but neither L-NAME nor sildenafil altered such recruitment (Fig 5A). Conversely, CD11b+Gr1+ cells dropped by 50% in the blood of tumor-bearing mice treated with either L-NAME or sildenafil, when compared with samples collected from untreated tumor-bearing mice (Fig. 5B). This was not confirmed in the RMA model, despite a comparable recruitment of CD11b+Gr1+ cells (Fig. 5D). Hence, L-NAME, although highly effective in restraining tumor growth in both models, do not appear to consistently perturb the tumor-associated recruitment of CD11b+Gr1+ cells. To gain further insight on the mechanism underlying the therapeutic effect of L-NAME, we assessed the enzymatic activity of MDSC cells purified from the spleen of RMA-bearing mice. Magnetic bead-purified CD11b+ cells from L-NAME treated animals showed a relevant reduction in Arg activity when compared with those obtained from control animals treated with vehicle (Fig. 5E), therefore confirming that in vivo L-NAME is a potent inhibitor of Arg [34].


Modulators of arginine metabolism support cancer immunosurveillance.

Capuano G, Rigamonti N, Grioni M, Freschi M, Bellone M - BMC Immunol. (2009)

Modulators of arginine metabolism alter MDSC accumulation in the blood of tumor-bearing mice. BALB/c and C57BL/6 mice were challenged s.c. with C26GM and RMA cells, respectively. The same day, mice were randomly assigned to either one of the following treatments: L-NAME or sildenafil (given i.p. or dissolved in drinking water) or vehicle (PBS; V) i.p. (see Materials and Methods section for experimental details). Tumor-bearing BALB/c and C57BL/6 mice were killed 9 and 15 day later. Recruitment of CD11b+Gr1- and CD11b+Gr1+ cells in the spleen (A, C) and blood (B, D) of tumor-bearing BALB/c (A, B) and C57BL/6 mice (C, D) was investigated by flow cytometry. Histograms report the percentage of CD11b+ Gr1- and CD11b+ Gr1+ cells as aggregated data (average ± SD) for the experimental groups reported in the legend of Fig. 3. Alternatively, magnetic bead sorted CD11b+ cells from the spleen of RMA (E) tumor bearing mice were lysed and analyzed for relative Arg enzyme activity. Student's T test: ***p < 0.001, **0.001 < p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 5: Modulators of arginine metabolism alter MDSC accumulation in the blood of tumor-bearing mice. BALB/c and C57BL/6 mice were challenged s.c. with C26GM and RMA cells, respectively. The same day, mice were randomly assigned to either one of the following treatments: L-NAME or sildenafil (given i.p. or dissolved in drinking water) or vehicle (PBS; V) i.p. (see Materials and Methods section for experimental details). Tumor-bearing BALB/c and C57BL/6 mice were killed 9 and 15 day later. Recruitment of CD11b+Gr1- and CD11b+Gr1+ cells in the spleen (A, C) and blood (B, D) of tumor-bearing BALB/c (A, B) and C57BL/6 mice (C, D) was investigated by flow cytometry. Histograms report the percentage of CD11b+ Gr1- and CD11b+ Gr1+ cells as aggregated data (average ± SD) for the experimental groups reported in the legend of Fig. 3. Alternatively, magnetic bead sorted CD11b+ cells from the spleen of RMA (E) tumor bearing mice were lysed and analyzed for relative Arg enzyme activity. Student's T test: ***p < 0.001, **0.001 < p < 0.05.
Mentions: We investigated whether treatment with L-NAME or sildenafil modified accrual of MDSC in the spleen and blood of tumor-challenged mice. Flow cytometry analyses conducted ex vivo the day of mouse killing showed a clear accumulation of both CD11b+Gr1+ and CD11b+Gr1- cells in the spleen of BALB/c mice bearing C26GM tumors, but neither L-NAME nor sildenafil altered such recruitment (Fig 5A). Conversely, CD11b+Gr1+ cells dropped by 50% in the blood of tumor-bearing mice treated with either L-NAME or sildenafil, when compared with samples collected from untreated tumor-bearing mice (Fig. 5B). This was not confirmed in the RMA model, despite a comparable recruitment of CD11b+Gr1+ cells (Fig. 5D). Hence, L-NAME, although highly effective in restraining tumor growth in both models, do not appear to consistently perturb the tumor-associated recruitment of CD11b+Gr1+ cells. To gain further insight on the mechanism underlying the therapeutic effect of L-NAME, we assessed the enzymatic activity of MDSC cells purified from the spleen of RMA-bearing mice. Magnetic bead-purified CD11b+ cells from L-NAME treated animals showed a relevant reduction in Arg activity when compared with those obtained from control animals treated with vehicle (Fig. 5E), therefore confirming that in vivo L-NAME is a potent inhibitor of Arg [34].

Bottom Line: Tumor-associated accrual of myeloid derived suppressor cells (MDSC) in the blood, lymphoid organs and tumor tissues may lead to perturbation of the arginine metabolism and impairment of the endogenous antitumor immunity.Treatment of tumor-bearing mice with either the phosphodiesterase-5 inhibitor sildenafil or the nitric-oxide synthase (NOS) inhibitor L-NAME significantly restrained tumor growth and expanded the tumor-specific immune response.Our data emphasize the role of MDSC in modulating the endogenous tumor-specific immune response and underline the anti-neoplastic therapeutic potential of arginine metabolism modulators.

View Article: PubMed Central - HTML - PubMed

Affiliation: Cancer Immunotherapy and Gene Therapy Program, Istituto Scientifico San Raffaele, Via Olgettina 58, 20132, Milan, Italy. giusy_capuano@hotmail.com

ABSTRACT

Background: Tumor-associated accrual of myeloid derived suppressor cells (MDSC) in the blood, lymphoid organs and tumor tissues may lead to perturbation of the arginine metabolism and impairment of the endogenous antitumor immunity. The objective of this study was to evaluate whether accumulation of MDSC occurred in Th2 prone BALB/c and Th1 biased C57BL/6 mice bearing the C26GM colon carcinoma and RMA T lymphoma, respectively, and to investigate whether N(G) nitro-L-arginine methyl ester (L-NAME) and sildenafil, both modulators of the arginine metabolism, restored antitumor immunity.

Results: We report here that MDSC accumulate in the spleen and blood of mice irrespective of the mouse and tumor model used. Treatment of tumor-bearing mice with either the phosphodiesterase-5 inhibitor sildenafil or the nitric-oxide synthase (NOS) inhibitor L-NAME significantly restrained tumor growth and expanded the tumor-specific immune response.

Conclusion: Our data emphasize the role of MDSC in modulating the endogenous tumor-specific immune response and underline the anti-neoplastic therapeutic potential of arginine metabolism modulators.

Show MeSH
Related in: MedlinePlus