IGF1R and insulin receptor (IR) regulate biology of estrogen positive (ER+) and triple negative breast cancer (TNBC) cells. The results of initial clinical trials with anti-IGF1R drugs have been disappointing due to feedback upregulation of insulin receptor (IR) signaling and absence of biomarkers for these drugs.

We evaluated the effects of BMS-754807, a dual tyrosine kinase inhibitor of IGF1R/IR on ER+ and TNBC. In ER+ MCF-7 cells, it inhibited xenograft growth of MCF-7 tumors (n = 10 per treatment) compared to vehicle. Interestingly, while tumor growth was suppressed over a period of five weeks, eventually the tumors displayed resistance to BMS-754807. In TNBC, it inhibited motility in vitro. In contrast to ER+ cells, BMS-754807 did not inhibit primary tumor growth of TNBC cells injected into the mammary fat pad of mice. But at a dose of 50 mg/kg daily inhibited metastasis of TNBC cells, MDA-231-LM2 and MDA-MB435A/LCC6 cells, in the orthotopic and tail vein models of metastasis compared to vehicle (n = 10/group). Our data indicate that regulation of metastasis and tumor growth by IGF1R can be discrete events and functional imaging to identify biological properties of metastatic breast cancer regulated by IGF1R/IR are needed to better define treatments. While MRI is a powerful tool for detecting and imaging cancer, its utility in imaging metastasis to the lung is limited due to the challenges of lung MRI with conventional 3D gradient echo (GRE). MRI does not visualize lung well, mainly due to the abundance of air-tissue interfaces, which cause the MR signal to decay too rapidly for conventional MRI pulse sequences to capture. Clinically metastases are monitored by CT or PET but exposure of patients to ionizing radiation is a concern and problematic in longitudinal studies monitoring response to a targeted drug. Therefore, we recently reported the utility of a novel MR sequence called sweep imaging with Fourier transformation (SWIFT), where the data is acquired quasi-simultaneously with the radiofrequency pulse, to image lung metastasis of breast cancer. Here, we monitored response to IGF1R and IGF1R/IR targeted drugs in preclinical models of lung metastasis of breast cancer. We used MDA-231-LM2 cells with the tail vein injection model of metastasis. Mice with breast cancer metastases in the lungs were treated with either huEM164, an antibody against IGF1R, or BMS-754807. Metastasis was monitored by BLI and SWIFT MRI weekly. SWIFT was more sensitive in detecting inhibition of metastasis by these drugs.

Thus, dual inhibition of IGF1R and IR is effective in blocking growth of ER+ and metastasis of TNBC. However, combination of this therapeutic strategy with other agents may be necessary to prevent or delay onset of resistance. Further, noninvasive biomarkers of response to IGF1R/IR targeted drugs can be developed with SWIFT imaging.

Citation Format: Deepali Sachdev, Huy Donguyen, Naoharu Kobayashi, Sidath C. Kumarapperuma, Joeseph C. Weber. Functional imaging markers for blockade of breast cancer metastasis by IGF1R and insulin receptor targeted drugs using novel MRI and targeted iron oxide nanoparticles. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4248.