Modulation of the Tumor Microenvironment with Trastuzumab Enables Radiosensitization in HER2+ Breast Cancer

Abstract

DNA damage repair and tumor hypoxia contribute to intratumoral cellular and molecular heterogeneity and affect radiation response. The goal of this study is to investigate anti-HER2-induced radiosensitization of the tumor microenvironment to enhance fractionated radiotherapy in models of HER2+ breast cancer. This is monitored through in vitro and in vivo studies of phosphorylated γ-H2AX, [18F]-fluoromisonidazole (FMISO)-PET, and transcriptomic analysis. In vitro, HER2+ breast cancer cell lines were treated with trastuzumab prior to radiation and DNA double-strand breaks (DSB) were quantified. In vivo, HER2+ human cell line or patient-derived xenograft models were treated with trastuzumab, fractionated radiation, or a combination and monitored longitudinally with [18F]-FMISO-PET. In vitro DSB analysis revealed that trastuzumab administered prior to fractionated radiation increased DSB. In vivo, trastuzumab prior to fractionated radiation significantly reduced hypoxia, as detected through decreased [18F]-FMISO SUV, synergistically improving long-term tumor response. Significant changes in IL-2, IFN-gamma, and THBS-4 were observed in combination-treated tumors. Trastuzumab prior to fractionated radiation synergistically increases radiotherapy in vitro and in vivo in HER2+ breast cancer which is independent of anti-HER2 response alone. Modulation of the tumor microenvironment, through increased tumor oxygenation and decreased DNA damage response, can be translated to other cancers with first-line radiation therapy.

Polyclonal antibody-induced downregulation of HER1/EGFR and HER2 surpasses the effect of combinations of specific registered antibodies

“…Of note, the concentration used for anti-HER1 MAbs (that is, 10 µg/ml for cetuximab and nimotuzumab) was consistent with previous literature reports where these MAbs were used in vitro ( 34 , 37 ). Likewise, the concentration of anti-HER2 MAb, trastuzumab, agreed with additional literature reports ( 38 , 39 ). As before, PAbs-induced degradation of HER1 and HER2 exceeded HER1-specific or HER2-specific MAbs and their combinations in H292 cells, as evidenced by immunoblotting ( Figure 3C ) and quantitative ELISA ( Figures 3D , E ).…”

Quantifying the Effects of Combination Trastuzumab and Radiation Therapy in Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer

“…Radiation therapy can reduce recurrence rates in patients by eradicating the remaining cancer cells after the surgical removal of tumors; however, HER2+ patients have greater chances of recurrence than HER2- patients [ 11 , 26 ]. In vitro evidence suggests that trastuzumab can sensitize HER2+ breast cancer cells to radiation through the inhibition of signaling pathways involved in DNA repair mechanisms [ 7 , 27 , 28 ], although, systematic evaluations of the order of therapies and longitudinal data of cell responses are limited. This study demonstrates that the order of therapy does not alter cell proliferation after treatment, and longitudinal treatment effects are additive in vitro.…”

“…Immuno–PET imaging is an alternative method that could longitudinally evaluate immune infiltration after treatment [ 31 ]. 18 F-Fluoromisonidazole positron emission tomography is one method used to monitor the tumor oxygenation levels, and dynamic contrast-enhanced magnetic resonance imaging is an alternative method to quantitatively assess vascularity [ 27 , 30 ]. Neither of these methods would allow for histological validation at every time point; however, they would offer finely time-resolved data of tumor status over the course of treatment.…”

Molecular and serological biomarkers to predict trastuzumab responsiveness in HER-2 positive breast cancer

“…Despite a year-long trastuzumab treatment (17 cycles), over 20% of patients experience recurrence or metastasis, demonstrating the complexity and heterogeneity of the tumor [ 5 ]. Unfortunately, there are no currently available noninvasive biomarkers that can accurately detect a patient's responsiveness to trastuzumab [ 6 ]. Finding new treatments to overcome trastuzumab treatment failure is essential to improve mortality in HER-2-positive metastatic breast cancer [ 7 , 8 ].…”