FY25 Overcoming Treatment Resistance in Wilms Tumor by PT

Overcoming Treatment Resistance in Wilms Tumor by Precision Targeting with Radiopharmaceuticals Project Summary/Abstract (limit one page) Wilms tumor, also known as nephroblastoma, is the most common renal malignancy in children. The long-term survival rates for Wilms tumor in patients with localized disease are high, but morbidity is often associated with treatment in these patients. Moreover, several studies have indicated that Wilms tumors with anaplastic histology are associated with higher rates of recurrence, metastases, and death. There is an urgent need therefore to develop new treatment options to overcome therapy resistance and also minimize the risk of secondary tumors caused by treatment. The focus of the activities in this supplement is to develop a strategy that employs radio- pharmaceuticals with an emission range of 2-mm to selectively target cell surface GRP78 (csGRP78) on the Wilms tumor cells. This approach will induce endoplasmic reticulum (ER)-stress and a DNA damage response (DDR) to produce irreparable damage only in cancer cells, overcome treatment resistance, and cause growth inhibition of Wilms tumor. This approach involves targeting csGRP78 with a cyclic-peptide that is cell-penetrating and reaches the ER to induce ER-stress. As this csGRP78- binding peptide is not expected to cause cell death on it’s own, we will attached a radionuclide emitting β- particles to it as a therapeutic payload to cause DNA damage. By selectively binding to the cancer cells and co-inducing ER-stress and DDR, the radiolabeled csGRP78-binding peptide will trigger extreme stress and cell death in cancer cells, but not in the normal cells. We will determine the relationship between Wilms tumor 1 (WT1) protein, csGRP78 expression, and Par-4, which binds to WT1 and csGRP78 and regulates their function. The goals of the project are to perform pharmacokinetics/biodistribution studies on csGRP78- binding peptide in tumor bearing mice to trace targeting of the tumors by the radiolabeled peptide. These studies will use 68Ga, a positron (β+) emitter, as a radiotracer for detection of the csGRP78- binding peptide by micro-PET (Positron Emission Tomography) imaging. The therapeutic outcome of inducing ER-stress, DNA damage, and cell death proteins will be validated in cell culture and tumor xenografts by using 177Lu, an electron (β-) particle emitting radiolabel as a therapeutic payload to induce irreparable damage and cell death selectively in the cancer cells. As the energy emission range of 177Lu is 2-mm in tissues, we expect that csGRP78+ tumor cells that bind to the radiolabeled-peptide will show ER-stress, DDR, robust caspase activation and apoptotic cell death, and the neighboring cancer cells within the 2-mm range of the target cells will also show ER-stress and DDR owing to the radiation emitted. Most of the normal cells will not bind to the radiolabeled peptide and normal cells are generally known to be resistant to ER-stress. We will monitor adverse effects of radiopharmaceuticals, especially accumulation and increased risk of secondary cancers in the kidney and bone marrow of mice. Together with immuno-histochemistry for ER-stress, DDR, and cell survival or cell death associated proteins, and digital image analysis, these studies will elucidate the effects of targeting csGRP78 with the radiolabeled-peptide on cell fate (i.e., survival or cell death) in normal and tumor tissues. The relationship between Par-4 and csGRP78 was established by us and other laboratories and that between Par-4 and WT1 protein is previously published by us and will be further examined in the parent grant. The studies proposed in this Supplement will extend the impact of the parent grant in relation to childhood cancer by providing a better understanding of the relationship between WT1 and csGRP78, and testing csGRP78 as a direct target to precisely kill Wilms tumor cells without the side effects noted with current chemotherapy or external bean radiation treatment. The findings will provide the biological and mechanistic framework for using csGRP78-targeting radiopharmaceuticals for robust growth inhibition of Wilms tumor.