CANCER BIOTHERAPY AND RADIOPHARMACEUTICALS Volume 29, Number 6, 2014 ª Mary Ann Liebert, Inc. DOI: 10.1089/cbr.2013.1583
Pazopanib Combined with Radiation: In Vivo Model of Interaction Ruby F. Meredith,1,* Kevin P. Raisch,1,*,{ James A. Bonner,1 Donald J. Buchsbaum,1 Willliam E. Grizzle,2 Yufeng Li,3 and Sharon A. Spencer1
Abstract
Objective: Assess interaction of pazopanib, an oral antivascular endothelial growth factor inhibitor, with radiation in tumor xenograft models. Methods: Flank xenografts in female athymic nude mice of human lung cancer cell line, A549, and head and neck cancer cell line, UM-SCC-6, were allowed to grow to *5 · 5 mm. Groups were then treated with pazopanib and/or escalating doses of radiation and tumor measurements over time compared with untreated tumor-bearing controls. Pazopanib (100 mg/kg) began 7 days before radiation and continued for 28 days. Daily radiation was 0.5, 1, 2, or 3 Gy · 5 days. Results: Tumors in the A549 control group reached > 4 · the original size by day 36 postradiation. All treatment groups had less robust tumor growth ( p < 0.05) and the group receiving pazopanib + 3 Gy radiation/ day had tumor regression to less than baseline. In the UM-SCC-6-tumor-bearing animals, tumors in all treatment groups had less robust growth than untreated controls after day 23 post-treatment. Conclusion: The combination of pazopanib and radiation resulted in a trend of superior tumor growth inhibition compared with either agent alone. All treatment groups had impaired tumor progression compared with untreated controls. Key words: pazopanib, radiation, xenograft tumor model
Introduction
P
azopanib is an oral angiogenesis inhibitor targeting the tyrosine kinase activity associated with vascular endothelial growth factor (VEGF) receptors (VEGFR-1, -2 and -3), platelet-derived growth factor receptors-a and -b, and stem cell factor (c-KIT). Pazopanib is approved for the treatment of advanced renal cell carcinoma plus metastatic soft tissue sarcomas and is under study for other malignancies.1–4 Investigational studies involve its use in conjunction with other agents, including study in cooperative group trials.5,6 Although published clinical trials and multiple preclinical studies have used pazopanib with chemotherapies/biologics, basic reports of its interaction with radiation are lacking. One clinical report testing the combination of radiation and
pazopanib found it tolerable for skin toxicity, but did not assess for improved efficacy over radiation alone.1 A positive interaction is anticipated as other antiangiogenesis VEGF inhibitors are known to be radiosensitizers.7,8 This study examines the interaction of pazopanib with radiation in two in vivo models as a step to better understanding its clinical utility for cancer therapy. Materials and Methods
The nonsmall cell lung cancer cell line, A549, and the head and neck cancer cell line, UM-SCC-6, were used to establish xenografts in female athymic nude mice. Separately for each cell line, 5 · 106 cells (UM-SCC-6) or 2 · 106 cells (A549) mixed with Matrigel were injected subcutaneously
Departments of 1Radiation Oncology, 2Pathology, and 3Medicine, University of Alabama at Birmingham, Birmingham, Alabama. *These authors contributed equally to the work. { Current address: Department of Otolaryngology, University of Florida, Gainesville, Florida. Address correspondence to: Ruby F. Meredith; Hazelrig Salter Radiation Oncology Center; 1700 6th Avenue South, 176F, Birmingham, AL, 35249 E-mail: [email protected]
247
248
into the flank and tumors allowed to grow to *5 · 5 mm. Groups of 10 mice were then treated with pazopanib or vehicle (30% Captisol; CyDex Pharmaceuticals, Inc., Lenexa, KS) and/or escalating doses of radiation (IC-320; Kimtron, Inc., Woodbury, CT), and tumor measurements over time compared with untreated tumor-bearing controls (Captisol vehicle only) for 50 days. Pazopanib was given at 100 mg/kg by oral gavage, beginning 7 days before radiation and continuing for a total of 28 days. The choice of 100 mg/kg oral dose is based on preclinical studies where a dose/response of tumor inhibition was observed, with oral 100 mg/kg once or twice daily being the highest dose and comparing favorably to subcutaneous administration through continuous infusion.9 These pharmacokinetic/pharmacodynamic studies showed that a pazopanib concentration of *40 lmol/L, which was achieved by 100 mg/kg, is required for maximum inhibition of VEGFR2 and inhibited multiple other kinases in mouse lung.9 Results from these murine studies were applied to a Phase I clinical trial as a target steadystate concentration of ‡ 40 lmol/L. Near this concentration was achieved in the majority of patients receiving doses of ‡ 800 mg once daily or 300 mg twice daily (mean trough concentration 34 lmol/L).10 Although dosing ranged up to 2000 mg/day, most patients reached acceptable steady-state levels at the 800 mg dose, which has become the recommended dose for FDA approved use in patients with renal cell carcinoma and is being studied in other malignancies.11 Daily radiation dose was 0.5, 1, 2, or 3 Gy · 5 days. The repeat experiment used 2 · 106 UM-SCC-6 cells and the 3 Gy treatment group was replaced by a 0.5 Gy group. Data were combined from two A549 animal experiments (n = 20) to evaluate if tumor growth was associated with treatment regimens and over time using a longitudinal analysis method with a mixed model procedure. Experiment days from the two data sets were combined for measures – 1 day. If an animal was euthanized due to the size of tumor, that tumor size was carried forward to subsequent study days. Univariate and multivariate analysis were used.
FIG. 1. Comparison of A549 mean tumor xenograft growth over time for untreated controls, and groups of mice treated with pazopanib and/or 1 or 3 Gy radiation/day · 5 days (n = 10 mice/group). Error bars represent – SD.
MEREDITH ET AL. Biomarker studies
Thirty-one randomly selected animals were sacrificed on day 20 for A549 tumors and day 28 for UM-SCC-6 tumors. Tumors taken at the time of sacrifice were processed into blocks. Slides cut from each block were stained for Ki67 as a biomarker of proliferation, CD31 for angiogenesis, or with H&E to aid the pathologist in review for necrosis. Correlation analysis between biomarkers and tumor size was performed using the tumor size at day 17 since this was close to the time of sacrifice. Results
The growth pattern for most groups bearing A549 lung cancer xenografts initially treated (n = 10) is shown in Figure 1. Multivariate analysis showed that the tumor size significantly increased over time ( p < 0.001) for all groups, and that changes of tumor size were different by treatment groups over time ( p < 0.0001). In the A549 untreated control group, tumors reached greater than 4 · the original tumor size before day 26 and some animals were euthanized due to a large tumor burden. Among the treatment groups, only one animal in the 1 Gy group and one that received pazopanib alone had to be euthanized due to a large tumor burden. The group receiving the most aggressive treatment of pazopanib + 3 Gy radiation/day had tumor regression to less than baseline by day 21 postradiation treatment. Although 2 Gy groups are not shown in Figure 1 for simplicity, the growth patterns were relatively similar and slightly less favorable for 2 Gy versus 3 Gy – pazopanib and these were not statistically different (Table 1). The repeat experiment had similar patterns, showing a greater efficacy with increasing radiation and a trend of improved inhibition with the addition of pazopanib. Table 1 provides a comparison of most A459 xenografts, with data combined from the two experiments for the repeat groups. As shown in Table 1, where shaded rows indicate comparisons that were statistically different, the tumor size in all treatment groups was significantly less than untreated control tumors ( p < 0.0001).
PAZOPANIB PLUS RADIATION IN XENOGRAFT TUMOR MODEL
Table 1. Comparison of Tumor Growth in Untreated Control Mice and Various Treatment Groups Group 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 2 Gy 2 Gy 2 Gy 2 Gy 2 Gy 2 Gy 3 Gy 3 Gy 3 Gy 3 Gy 3 Gy Pazopanib Pazopanib Pazopanib Pazopanib Pazopanib + 1 Pazopanib + 1 Pazopanib + 1 Pazopanib + 2 Pazopanib + 2 Pazopanib + 3
Group
Gy Gy Gy Gy Gy Gy
2 Gy 3 Gy Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control 3 Gy Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 3 Control Control
Gy Gy Gy
Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy
Estimatea
Adjusted p-value
73 98 41 75 106 127 - 162 25 - 32 2 33 54 - 235 - 57 - 23 8 29 - 270 33 65 86 - 203 31 52 - 237 21 - 268 - 289
0.1041 0.0054 0.7576 0.0829 0.0017 < 0.0001 < 0.0001 0.9798 0.9245 1.0000 0.9078 0.4406 < 0.0001 0.3606 0.9871 1.0000 0.9511 < 0.0001 0.8962 0.1992 0.0246 < 0.0001 0.9303 0.4844 < 0.0001 0.9932 < 0.0001 < 0.0001
This analysis includes combined data for the initial and repeat experiments (n = 20) for the 1 and 2 Gy groups; 3 Gy groups were only in the initial experiment. a Estimate rounded to nearest whole number; standard error was 25.9–26.2 for all.
249
Similar to the results in the A549 tumor-bearing animals, there is more tumor inhibition with higher radiation doses and a positive interaction between radiation and pazopanib in the UM-SCC-6 groups. An example of the interaction is shown in Figure 2, where tumor inhibition after 0.5 Gy is improved with the addition of pazopanib. In the UM-SCC-6tumor-bearing animals, tumors in all groups continued to grow during initial therapy and then declined by day 13 postradiation treatment. Those animals treated with pazopanib alone had a growth and regression pattern most similar to that of the untreated controls, whereas those receiving the combination of pazopanib and radiation had tumor regression below baseline. Confirming the radiation alone efficacy at the highest dose like the A459 groups, the UMSCC-6 tumor-bearing animals treated with 3 Gy/day had the most vigorous regression pattern, and some animals had complete response to treatment. There are no significant associations between the biomarkers studied and treatment group. The percent of cells staining for Ki67 ranged from 5 to 85, but did not show any association with the tumor size using the Pearson correlation measurement with rho = 0.1227, p = 0.5109. There was a trend of association of angiogenesis marker CD31 with tumor size at day 17, but this was not statistically significant even at the 10% level ( p = 0.1044). Categories of mild, moderate, and severe necrosis were used for the pathologist’s assessment of necrosis. There was a significant difference in tumor size by category ( p = 0.0004) with mean tumor size of 147 mm2, median 140 mm2, and range 120–196 mm2 in the mild necrosis group, whereas the mean was 132 mm2, median 125 mm2, with a range of 100– 168 mm2 in the moderate group, and the mean was 103 mm2, median 101 mm2, with a range 80–136 mm2 in the severe necrosis group. Discussion
Although the pattern of growth and treatment effects were different for the lung versus the head and neck cancer xenografts, both showed an enhanced tumor inhibition with the
FIG. 2. Comparison of UM-SCC-6 tumor xenograft growth over time for untreated controls, and groups treated with pazopanib and/or 5 days of 0.5 Gy radiation/day (n = 10 mice/group). Error bars represent – SD.
250
addition of pazopanib over radiation alone. There was a positive trend of interaction at all radiation dose levels studied, despite some not being statistically significant. The lack of correlation of tumor growth outcome with biomarkers of proliferation and angiogenesis leaves open the need for additional study to determine the mechanisms of interaction. Since pazopanib is a potent inhibitor of multiple tyrosine kinases, the evaluation of kinase activities in tumor specimens represents a feasible pretreatment assessment for biomarker development, but this has not yet been accomplished.12,13
MEREDITH ET AL.
3. 4. 5.
Conclusions
The combination of pazopanib and limited radiation resulted in a trend of superior inhibition of tumor growth compared with either agent alone. All treatment groups had impaired tumor progression compared with untreated controls.
6.
Acknowledgments
7.
The authors thank Sheila Bright and Leisa Seay for technical assistance in animal model studies, and Sally Wakefield for article preparation. Supported by Glaxo Smith Kline.
8.
Disclosure Statement
The author has no significant financial interests that are related to or would reasonably appear to be affected by the proposed article. All authors involved with the article have been informed of their obligations under federal regulations governing disclosure of significant financial interests and have no conflicts of interest or potential conflicts of interest that have not been disclosed.
9.
10. 11.
References
1. Goyal S, et al. Evaluation of acute locoregional toxicity in patients with breast cancer treated with adjuvant radiotherapy in combination with pazopanib. ISRN Oncol 2012; 2012:896202. 2. Johnston SR, et al. A randomized and open-label trial evaluating the addition of pazopanib to lapatinib as first-
12. 13.
line therapy in patients with HER2-positive advanced breast cancer. Breast Cancer Res Treat 2013;137:755. Reardon DA, et al. A phase I/II trial of pazopanib in combination with lapatinib in adult patients with relapsed malignant glioma. Clin Cancer Res 2013;19:900. Isham CR, et al. Pazopanib enhances paclitaxel-induced mitotic catastrophe in anaplastic thyroid cancer. Sci Transl Med 2013;5:p. 166ra3. R. T. O. Group. 2013. A Randomized Phase II Study of Concurrent Intensity Modulated Radiation Therapy (IMRT), Paclitaxel and Pazopanib (NSC 737754)/Placebo, for the Treatment of Anaplastic Thyroid Cancer (RTOG 0912). Available at rtog.org G. O. Group. A Randomized Phase II Evaluation of Weekly Paclitaxel Plus Pazopanib VS Weekly Paclitaxel Plus Placebo in the Treatment of Persistent or Recurrent Epithelial Ovarian, Fallopian Tube or Primary Peritoneal Carcinoma (GOG-0186J). Available at gog.org Nieder C, et al. Radiation therapy plus angiogenesis inhibition with bevacizumab: Rationale and initial experience. Rev Recent Clin Trials 2007;2:163. Hess C, et al. Effect of VEGF receptor inhibitor PTK787/ ZK222584 [correction of ZK222548] combined with ionizing radiation on endothelial cells and tumour growth. Br J Cancer 2001;85:2010. Kumar R, et al. Pharmacokinetic-pharmacodynamic correlation from mouse to human with pazopanib, a multikinase angiogenesis inhibitor with potent antitumor and antiangiogenic activity. Mol Cancer Ther 2007;6:2012. Hurwitz HI, et al. Phase I trial of pazopanib in patients with advanced cancer. Clin Cancer Res 2009;15:4220. Shibata SI, et al. Phase I study of pazopanib in patients with advanced solid tumors and hepatic dysfunction: A National Cancer Institute Organ Dysfunction Working Group study. Clin Cancer Res 2013;19:3631. Jarboe JS, et al. Mini-review: Bmx kinase inhibitors for cancer therapy. Recent Pat Anticancer Drug Discov 2013;8: 228. Jarboe JS, et al. Kinomic profiling approach identifies Trk as a novel radiation modulator. Radiother Oncol 2012; 103:380.
Pazopanib Combined with Radiation: In Vivo Model of Interaction Ruby F. Meredith,1,* Kevin P. Raisch,1,*,{ James A. Bonner,1 Donald J. Buchsbaum,1 Willliam E. Grizzle,2 Yufeng Li,3 and Sharon A. Spencer1
Abstract
Objective: Assess interaction of pazopanib, an oral antivascular endothelial growth factor inhibitor, with radiation in tumor xenograft models. Methods: Flank xenografts in female athymic nude mice of human lung cancer cell line, A549, and head and neck cancer cell line, UM-SCC-6, were allowed to grow to *5 · 5 mm. Groups were then treated with pazopanib and/or escalating doses of radiation and tumor measurements over time compared with untreated tumor-bearing controls. Pazopanib (100 mg/kg) began 7 days before radiation and continued for 28 days. Daily radiation was 0.5, 1, 2, or 3 Gy · 5 days. Results: Tumors in the A549 control group reached > 4 · the original size by day 36 postradiation. All treatment groups had less robust tumor growth ( p < 0.05) and the group receiving pazopanib + 3 Gy radiation/ day had tumor regression to less than baseline. In the UM-SCC-6-tumor-bearing animals, tumors in all treatment groups had less robust growth than untreated controls after day 23 post-treatment. Conclusion: The combination of pazopanib and radiation resulted in a trend of superior tumor growth inhibition compared with either agent alone. All treatment groups had impaired tumor progression compared with untreated controls. Key words: pazopanib, radiation, xenograft tumor model
Introduction
P
azopanib is an oral angiogenesis inhibitor targeting the tyrosine kinase activity associated with vascular endothelial growth factor (VEGF) receptors (VEGFR-1, -2 and -3), platelet-derived growth factor receptors-a and -b, and stem cell factor (c-KIT). Pazopanib is approved for the treatment of advanced renal cell carcinoma plus metastatic soft tissue sarcomas and is under study for other malignancies.1–4 Investigational studies involve its use in conjunction with other agents, including study in cooperative group trials.5,6 Although published clinical trials and multiple preclinical studies have used pazopanib with chemotherapies/biologics, basic reports of its interaction with radiation are lacking. One clinical report testing the combination of radiation and
pazopanib found it tolerable for skin toxicity, but did not assess for improved efficacy over radiation alone.1 A positive interaction is anticipated as other antiangiogenesis VEGF inhibitors are known to be radiosensitizers.7,8 This study examines the interaction of pazopanib with radiation in two in vivo models as a step to better understanding its clinical utility for cancer therapy. Materials and Methods
The nonsmall cell lung cancer cell line, A549, and the head and neck cancer cell line, UM-SCC-6, were used to establish xenografts in female athymic nude mice. Separately for each cell line, 5 · 106 cells (UM-SCC-6) or 2 · 106 cells (A549) mixed with Matrigel were injected subcutaneously
Departments of 1Radiation Oncology, 2Pathology, and 3Medicine, University of Alabama at Birmingham, Birmingham, Alabama. *These authors contributed equally to the work. { Current address: Department of Otolaryngology, University of Florida, Gainesville, Florida. Address correspondence to: Ruby F. Meredith; Hazelrig Salter Radiation Oncology Center; 1700 6th Avenue South, 176F, Birmingham, AL, 35249 E-mail: [email protected]
247
248
into the flank and tumors allowed to grow to *5 · 5 mm. Groups of 10 mice were then treated with pazopanib or vehicle (30% Captisol; CyDex Pharmaceuticals, Inc., Lenexa, KS) and/or escalating doses of radiation (IC-320; Kimtron, Inc., Woodbury, CT), and tumor measurements over time compared with untreated tumor-bearing controls (Captisol vehicle only) for 50 days. Pazopanib was given at 100 mg/kg by oral gavage, beginning 7 days before radiation and continuing for a total of 28 days. The choice of 100 mg/kg oral dose is based on preclinical studies where a dose/response of tumor inhibition was observed, with oral 100 mg/kg once or twice daily being the highest dose and comparing favorably to subcutaneous administration through continuous infusion.9 These pharmacokinetic/pharmacodynamic studies showed that a pazopanib concentration of *40 lmol/L, which was achieved by 100 mg/kg, is required for maximum inhibition of VEGFR2 and inhibited multiple other kinases in mouse lung.9 Results from these murine studies were applied to a Phase I clinical trial as a target steadystate concentration of ‡ 40 lmol/L. Near this concentration was achieved in the majority of patients receiving doses of ‡ 800 mg once daily or 300 mg twice daily (mean trough concentration 34 lmol/L).10 Although dosing ranged up to 2000 mg/day, most patients reached acceptable steady-state levels at the 800 mg dose, which has become the recommended dose for FDA approved use in patients with renal cell carcinoma and is being studied in other malignancies.11 Daily radiation dose was 0.5, 1, 2, or 3 Gy · 5 days. The repeat experiment used 2 · 106 UM-SCC-6 cells and the 3 Gy treatment group was replaced by a 0.5 Gy group. Data were combined from two A549 animal experiments (n = 20) to evaluate if tumor growth was associated with treatment regimens and over time using a longitudinal analysis method with a mixed model procedure. Experiment days from the two data sets were combined for measures – 1 day. If an animal was euthanized due to the size of tumor, that tumor size was carried forward to subsequent study days. Univariate and multivariate analysis were used.
FIG. 1. Comparison of A549 mean tumor xenograft growth over time for untreated controls, and groups of mice treated with pazopanib and/or 1 or 3 Gy radiation/day · 5 days (n = 10 mice/group). Error bars represent – SD.
MEREDITH ET AL. Biomarker studies
Thirty-one randomly selected animals were sacrificed on day 20 for A549 tumors and day 28 for UM-SCC-6 tumors. Tumors taken at the time of sacrifice were processed into blocks. Slides cut from each block were stained for Ki67 as a biomarker of proliferation, CD31 for angiogenesis, or with H&E to aid the pathologist in review for necrosis. Correlation analysis between biomarkers and tumor size was performed using the tumor size at day 17 since this was close to the time of sacrifice. Results
The growth pattern for most groups bearing A549 lung cancer xenografts initially treated (n = 10) is shown in Figure 1. Multivariate analysis showed that the tumor size significantly increased over time ( p < 0.001) for all groups, and that changes of tumor size were different by treatment groups over time ( p < 0.0001). In the A549 untreated control group, tumors reached greater than 4 · the original tumor size before day 26 and some animals were euthanized due to a large tumor burden. Among the treatment groups, only one animal in the 1 Gy group and one that received pazopanib alone had to be euthanized due to a large tumor burden. The group receiving the most aggressive treatment of pazopanib + 3 Gy radiation/day had tumor regression to less than baseline by day 21 postradiation treatment. Although 2 Gy groups are not shown in Figure 1 for simplicity, the growth patterns were relatively similar and slightly less favorable for 2 Gy versus 3 Gy – pazopanib and these were not statistically different (Table 1). The repeat experiment had similar patterns, showing a greater efficacy with increasing radiation and a trend of improved inhibition with the addition of pazopanib. Table 1 provides a comparison of most A459 xenografts, with data combined from the two experiments for the repeat groups. As shown in Table 1, where shaded rows indicate comparisons that were statistically different, the tumor size in all treatment groups was significantly less than untreated control tumors ( p < 0.0001).
PAZOPANIB PLUS RADIATION IN XENOGRAFT TUMOR MODEL
Table 1. Comparison of Tumor Growth in Untreated Control Mice and Various Treatment Groups Group 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 1 Gy 2 Gy 2 Gy 2 Gy 2 Gy 2 Gy 2 Gy 3 Gy 3 Gy 3 Gy 3 Gy 3 Gy Pazopanib Pazopanib Pazopanib Pazopanib Pazopanib + 1 Pazopanib + 1 Pazopanib + 1 Pazopanib + 2 Pazopanib + 2 Pazopanib + 3
Group
Gy Gy Gy Gy Gy Gy
2 Gy 3 Gy Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control 3 Gy Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 1 Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 2 Pazopanib + 3 Control Pazopanib + 3 Control Control
Gy Gy Gy
Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy Gy
Estimatea
Adjusted p-value
73 98 41 75 106 127 - 162 25 - 32 2 33 54 - 235 - 57 - 23 8 29 - 270 33 65 86 - 203 31 52 - 237 21 - 268 - 289
0.1041 0.0054 0.7576 0.0829 0.0017 < 0.0001 < 0.0001 0.9798 0.9245 1.0000 0.9078 0.4406 < 0.0001 0.3606 0.9871 1.0000 0.9511 < 0.0001 0.8962 0.1992 0.0246 < 0.0001 0.9303 0.4844 < 0.0001 0.9932 < 0.0001 < 0.0001
This analysis includes combined data for the initial and repeat experiments (n = 20) for the 1 and 2 Gy groups; 3 Gy groups were only in the initial experiment. a Estimate rounded to nearest whole number; standard error was 25.9–26.2 for all.
249
Similar to the results in the A549 tumor-bearing animals, there is more tumor inhibition with higher radiation doses and a positive interaction between radiation and pazopanib in the UM-SCC-6 groups. An example of the interaction is shown in Figure 2, where tumor inhibition after 0.5 Gy is improved with the addition of pazopanib. In the UM-SCC-6tumor-bearing animals, tumors in all groups continued to grow during initial therapy and then declined by day 13 postradiation treatment. Those animals treated with pazopanib alone had a growth and regression pattern most similar to that of the untreated controls, whereas those receiving the combination of pazopanib and radiation had tumor regression below baseline. Confirming the radiation alone efficacy at the highest dose like the A459 groups, the UMSCC-6 tumor-bearing animals treated with 3 Gy/day had the most vigorous regression pattern, and some animals had complete response to treatment. There are no significant associations between the biomarkers studied and treatment group. The percent of cells staining for Ki67 ranged from 5 to 85, but did not show any association with the tumor size using the Pearson correlation measurement with rho = 0.1227, p = 0.5109. There was a trend of association of angiogenesis marker CD31 with tumor size at day 17, but this was not statistically significant even at the 10% level ( p = 0.1044). Categories of mild, moderate, and severe necrosis were used for the pathologist’s assessment of necrosis. There was a significant difference in tumor size by category ( p = 0.0004) with mean tumor size of 147 mm2, median 140 mm2, and range 120–196 mm2 in the mild necrosis group, whereas the mean was 132 mm2, median 125 mm2, with a range of 100– 168 mm2 in the moderate group, and the mean was 103 mm2, median 101 mm2, with a range 80–136 mm2 in the severe necrosis group. Discussion
Although the pattern of growth and treatment effects were different for the lung versus the head and neck cancer xenografts, both showed an enhanced tumor inhibition with the
FIG. 2. Comparison of UM-SCC-6 tumor xenograft growth over time for untreated controls, and groups treated with pazopanib and/or 5 days of 0.5 Gy radiation/day (n = 10 mice/group). Error bars represent – SD.
250
addition of pazopanib over radiation alone. There was a positive trend of interaction at all radiation dose levels studied, despite some not being statistically significant. The lack of correlation of tumor growth outcome with biomarkers of proliferation and angiogenesis leaves open the need for additional study to determine the mechanisms of interaction. Since pazopanib is a potent inhibitor of multiple tyrosine kinases, the evaluation of kinase activities in tumor specimens represents a feasible pretreatment assessment for biomarker development, but this has not yet been accomplished.12,13
MEREDITH ET AL.
3. 4. 5.
Conclusions
The combination of pazopanib and limited radiation resulted in a trend of superior inhibition of tumor growth compared with either agent alone. All treatment groups had impaired tumor progression compared with untreated controls.
6.
Acknowledgments
7.
The authors thank Sheila Bright and Leisa Seay for technical assistance in animal model studies, and Sally Wakefield for article preparation. Supported by Glaxo Smith Kline.
8.
Disclosure Statement
The author has no significant financial interests that are related to or would reasonably appear to be affected by the proposed article. All authors involved with the article have been informed of their obligations under federal regulations governing disclosure of significant financial interests and have no conflicts of interest or potential conflicts of interest that have not been disclosed.
9.
10. 11.
References
1. Goyal S, et al. Evaluation of acute locoregional toxicity in patients with breast cancer treated with adjuvant radiotherapy in combination with pazopanib. ISRN Oncol 2012; 2012:896202. 2. Johnston SR, et al. A randomized and open-label trial evaluating the addition of pazopanib to lapatinib as first-
12. 13.
line therapy in patients with HER2-positive advanced breast cancer. Breast Cancer Res Treat 2013;137:755. Reardon DA, et al. A phase I/II trial of pazopanib in combination with lapatinib in adult patients with relapsed malignant glioma. Clin Cancer Res 2013;19:900. Isham CR, et al. Pazopanib enhances paclitaxel-induced mitotic catastrophe in anaplastic thyroid cancer. Sci Transl Med 2013;5:p. 166ra3. R. T. O. Group. 2013. A Randomized Phase II Study of Concurrent Intensity Modulated Radiation Therapy (IMRT), Paclitaxel and Pazopanib (NSC 737754)/Placebo, for the Treatment of Anaplastic Thyroid Cancer (RTOG 0912). Available at rtog.org G. O. Group. A Randomized Phase II Evaluation of Weekly Paclitaxel Plus Pazopanib VS Weekly Paclitaxel Plus Placebo in the Treatment of Persistent or Recurrent Epithelial Ovarian, Fallopian Tube or Primary Peritoneal Carcinoma (GOG-0186J). Available at gog.org Nieder C, et al. Radiation therapy plus angiogenesis inhibition with bevacizumab: Rationale and initial experience. Rev Recent Clin Trials 2007;2:163. Hess C, et al. Effect of VEGF receptor inhibitor PTK787/ ZK222584 [correction of ZK222548] combined with ionizing radiation on endothelial cells and tumour growth. Br J Cancer 2001;85:2010. Kumar R, et al. Pharmacokinetic-pharmacodynamic correlation from mouse to human with pazopanib, a multikinase angiogenesis inhibitor with potent antitumor and antiangiogenic activity. Mol Cancer Ther 2007;6:2012. Hurwitz HI, et al. Phase I trial of pazopanib in patients with advanced cancer. Clin Cancer Res 2009;15:4220. Shibata SI, et al. Phase I study of pazopanib in patients with advanced solid tumors and hepatic dysfunction: A National Cancer Institute Organ Dysfunction Working Group study. Clin Cancer Res 2013;19:3631. Jarboe JS, et al. Mini-review: Bmx kinase inhibitors for cancer therapy. Recent Pat Anticancer Drug Discov 2013;8: 228. Jarboe JS, et al. Kinomic profiling approach identifies Trk as a novel radiation modulator. Radiother Oncol 2012; 103:380.
