TY - JOUR
T1 - Correlation Between Tumor Growth Delay and Expression of Cancer and Host VEGF, VEGFR2, and Osteopontin in Response to Radiotherapy
AU - Solberg, Timothy D.
AU - Nearman, Jessica
AU - Mullins, John
AU - Li, Sicong
AU - Baranowska-Kortylewicz, Janina
N1 - Funding Information:
Supported by Grant R01CA95267 (J. Baranowska-Kortylewicz), Department of Radiation Oncology, and American Cancer Society Grant 03-028-01-CCE (T. D. Solberg).
PY - 2008/11/1
Y1 - 2008/11/1
N2 - Purpose: To determine the late effects of radiotherapy (RT) on vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR2), and osteopontin (OPN) expression in cancer and stromal cells. Methods and Materials: LS174T xenografted athymic mice were used as a tumor model. Radiation was delivered in two equivalent fractionation schemes: 5 × 7 Gy and 1 × 20 Gy, the latter at two dose rates. Results: Tumor growth arrest was similar in all treatment groups, with the exception of a better response of small-size tumors in the 5 × 7-Gy group. The host VEGF and OPN levels were directly proportional to the tumor doubling time and were independent of the fractionation scheme. The host and cancer cell VEGFR2 levels in tumor were also directly related to the tumor response to RT. Conclusion: Upregulated VEGFR2 in cancer cells suggest paracrine signaling in the VEGFR2 pathway of cancer cells as the factor contributing to RT failure. The transient activation of the host VEGF/VEGFR2 pathway in tumor supports the model of angiogenic regeneration and suggests that radiation-induced upregulation of VEGF, VEGFR2, and downstream proteins might contribute to RT failure by escalating the rate of vascular repair. Coexpression of host OPN and VEGF, two factors closely associated with angiogenesis, indicate that OPN can serve as a surrogate marker of tumor recovery after RT. Taken together, these results strongly support the notion that to achieve optimal therapeutic outcomes, the scheduling of RT and antiangiogenic therapies will require patient-specific post-treatment monitoring of the VEGF/VEGFR2 pathway and that tumor-associated OPN can serve as an indicator of tumor regrowth.
AB - Purpose: To determine the late effects of radiotherapy (RT) on vascular endothelial growth factor (VEGF), VEGF receptor-2 (VEGFR2), and osteopontin (OPN) expression in cancer and stromal cells. Methods and Materials: LS174T xenografted athymic mice were used as a tumor model. Radiation was delivered in two equivalent fractionation schemes: 5 × 7 Gy and 1 × 20 Gy, the latter at two dose rates. Results: Tumor growth arrest was similar in all treatment groups, with the exception of a better response of small-size tumors in the 5 × 7-Gy group. The host VEGF and OPN levels were directly proportional to the tumor doubling time and were independent of the fractionation scheme. The host and cancer cell VEGFR2 levels in tumor were also directly related to the tumor response to RT. Conclusion: Upregulated VEGFR2 in cancer cells suggest paracrine signaling in the VEGFR2 pathway of cancer cells as the factor contributing to RT failure. The transient activation of the host VEGF/VEGFR2 pathway in tumor supports the model of angiogenic regeneration and suggests that radiation-induced upregulation of VEGF, VEGFR2, and downstream proteins might contribute to RT failure by escalating the rate of vascular repair. Coexpression of host OPN and VEGF, two factors closely associated with angiogenesis, indicate that OPN can serve as a surrogate marker of tumor recovery after RT. Taken together, these results strongly support the notion that to achieve optimal therapeutic outcomes, the scheduling of RT and antiangiogenic therapies will require patient-specific post-treatment monitoring of the VEGF/VEGFR2 pathway and that tumor-associated OPN can serve as an indicator of tumor regrowth.
KW - Osteopontin
KW - Stereotactic body radiotherapy
KW - VEGF
KW - VEGFR2
KW - Vascular endothelial growth factor
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U2 - 10.1016/j.ijrobp.2008.06.1925
DO - 10.1016/j.ijrobp.2008.06.1925
M3 - Article
C2 - 19014781
AN - SCOPUS:52949107240
SN - 0360-3016
VL - 72
SP - 918
EP - 926
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 3
ER -