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VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment
BACKGROUND: Targeting tumor vasculature is a strategy with great promise in the treatment of many cancers. However, anti-angiogenic reagents that target VEGF/VEGFR2 signaling have met with variable results clinically. Among the possible reasons for this may be heterogeneous expression of the target...
Autores principales: | , , , , , |
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Formato: | Texto |
Lenguaje: | English |
Publicado: |
BioMed Central
2010
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3009683/ https://www.ncbi.nlm.nih.gov/pubmed/21159176 http://dx.doi.org/10.1186/1471-2407-10-683 |
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author | Patten, Steven G Adamcic, Una Lacombe, Kristen Minhas, Kanwal Skowronski, Karolina Coomber, Brenda L |
author_facet | Patten, Steven G Adamcic, Una Lacombe, Kristen Minhas, Kanwal Skowronski, Karolina Coomber, Brenda L |
author_sort | Patten, Steven G |
collection | PubMed |
description | BACKGROUND: Targeting tumor vasculature is a strategy with great promise in the treatment of many cancers. However, anti-angiogenic reagents that target VEGF/VEGFR2 signaling have met with variable results clinically. Among the possible reasons for this may be heterogeneous expression of the target protein. METHODS: Double immunofluorescent staining was performed on formalin-fixed paraffin embedded sections of treated and control SW480 (colorectal) and WM239 (melanoma) xenografts, and tissue microarrays of human colorectal carcinoma and melanoma. Xenografts were developed using RAG1(-/- )mice by injection with WM239 or SW480 cells and mice were treated with 20 mg/kg/day of cyclophosphamide in their drinking water for up to 18 days. Treated and control tissues were characterized by double immunofluorescence using the mural cell marker α-SMA and CD31, while the ratio of desmin/CD31 was also determined by western blot. Hypoxia in treated and control tissues were quantified using both western blotting for HIF-1α and immunohistochemistry of CA-IX. RESULTS: VEGFR2 is heterogeneously expressed in tumor vasculature in both malignant melanoma and colorectal carcinoma. We observed a significant decrease in microvascular density (MVD) in response to low dose metronomic cyclophosphamide chemotherapy in both malignant melanoma (with higher proportion VEGFR2 positive blood vessels; 93%) and colorectal carcinoma (with lower proportion VEGFR2 positive blood vessels; 60%) xenografts. This reduction in MVD occurred in the absence of a significant anti-tumor effect. We also observed less hypoxia in treated melanoma xenografts, despite successful anti-angiogenic blockade, but no change in hypoxia of colorectal xenografts, suggesting that decreases in tumor hypoxia reflect a complex relationship with vascular density. Based on α-SMA staining and the ratio of desmin to CD31 expression as markers of tumor blood vessel functionality, we found evidence for increased stabilization of colorectal microvessels, but no such change in melanoma vessels. CONCLUSIONS: Overall, our study suggests that while heterogeneous expression of VEGFR2 is a feature of human tumors, it may not affect response to low dose metronomic cyclophosphamide treatment and possibly other anti-angiogenic approaches. It remains to be seen whether this heterogeneity is partly responsible for the variable clinical success seen to date with targeted anti-VEGFR2 therapy. |
format | Text |
id | pubmed-3009683 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2010 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-30096832010-12-24 VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment Patten, Steven G Adamcic, Una Lacombe, Kristen Minhas, Kanwal Skowronski, Karolina Coomber, Brenda L BMC Cancer Research Article BACKGROUND: Targeting tumor vasculature is a strategy with great promise in the treatment of many cancers. However, anti-angiogenic reagents that target VEGF/VEGFR2 signaling have met with variable results clinically. Among the possible reasons for this may be heterogeneous expression of the target protein. METHODS: Double immunofluorescent staining was performed on formalin-fixed paraffin embedded sections of treated and control SW480 (colorectal) and WM239 (melanoma) xenografts, and tissue microarrays of human colorectal carcinoma and melanoma. Xenografts were developed using RAG1(-/- )mice by injection with WM239 or SW480 cells and mice were treated with 20 mg/kg/day of cyclophosphamide in their drinking water for up to 18 days. Treated and control tissues were characterized by double immunofluorescence using the mural cell marker α-SMA and CD31, while the ratio of desmin/CD31 was also determined by western blot. Hypoxia in treated and control tissues were quantified using both western blotting for HIF-1α and immunohistochemistry of CA-IX. RESULTS: VEGFR2 is heterogeneously expressed in tumor vasculature in both malignant melanoma and colorectal carcinoma. We observed a significant decrease in microvascular density (MVD) in response to low dose metronomic cyclophosphamide chemotherapy in both malignant melanoma (with higher proportion VEGFR2 positive blood vessels; 93%) and colorectal carcinoma (with lower proportion VEGFR2 positive blood vessels; 60%) xenografts. This reduction in MVD occurred in the absence of a significant anti-tumor effect. We also observed less hypoxia in treated melanoma xenografts, despite successful anti-angiogenic blockade, but no change in hypoxia of colorectal xenografts, suggesting that decreases in tumor hypoxia reflect a complex relationship with vascular density. Based on α-SMA staining and the ratio of desmin to CD31 expression as markers of tumor blood vessel functionality, we found evidence for increased stabilization of colorectal microvessels, but no such change in melanoma vessels. CONCLUSIONS: Overall, our study suggests that while heterogeneous expression of VEGFR2 is a feature of human tumors, it may not affect response to low dose metronomic cyclophosphamide treatment and possibly other anti-angiogenic approaches. It remains to be seen whether this heterogeneity is partly responsible for the variable clinical success seen to date with targeted anti-VEGFR2 therapy. BioMed Central 2010-12-15 /pmc/articles/PMC3009683/ /pubmed/21159176 http://dx.doi.org/10.1186/1471-2407-10-683 Text en Copyright ©2010 Patten et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (<url>http://creativecommons.org/licenses/by/2.0</url>), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Article Patten, Steven G Adamcic, Una Lacombe, Kristen Minhas, Kanwal Skowronski, Karolina Coomber, Brenda L VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title | VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title_full | VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title_fullStr | VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title_full_unstemmed | VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title_short | VEGFR2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
title_sort | vegfr2 heterogeneity and response to anti-angiogenic low dose metronomic cyclophosphamide treatment |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3009683/ https://www.ncbi.nlm.nih.gov/pubmed/21159176 http://dx.doi.org/10.1186/1471-2407-10-683 |
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