Rong He

Supplementary Figures and Tables

Purpose: SMARCB1-deficient renal medullary carcinoma (RMC) is an ultrarare, lethal malignancy refractory to therapies approved for other renal cell carcinomas, and its rarity makes randomized trials logistically unfeasible. We investigated whether wild-type (WT) epidermal growth factor receptor (EGFR) is a therapeutically actionable dependency in RMC and translated this insight into a deployable clinical regimen. Experimental Design: EGFR expression was assessed by Clinical Laboratory Improvement Amendments–certified immunohistochemistry in RMC tumors and by integrated RNA and chromatin immunoprecipitation sequencing of primary tumors and adjacent kidney. Panitumumab was compared with erlotinib in patient- and cell line–derived xenografts, and its mechanism defined by immunoblotting, confocal co-localization, cell-cycle and apoptosis assays, and natural killer (NK) cell coculture. Panitumumab-based therapy was then evaluated prospectively in 26 patients with RMC across 10 centers on two continents. Results: RMC showed uniformly high membranous EGFR (median H-score 300), with enhancer and promoter reprogramming at the EGFR locus and a ligand switch from EGF to epiregulin and amphiregulin. EGFR expression was uncoupled from SMARCB1 status in vitro. Panitumumab outperformed erlotinib in RMC xenografts, suppressed AKT and ERK1/2 signaling, and routed EGFR to LAMP1-positive lysosomes in vitro; its effect was predominantly cytostatic, with minimal NK cell–mediated cytotoxicity. Clinically, panitumumab-based therapy achieved a 53.9% objective response rate, including 15.4% complete responses, with median progression-free and overall survival rates of 5.8 and 9.5 months, respectively. Conclusions: WT EGFR is a foundational dependency in RMC that is effectively targeted by panitumumab-based therapy. These findings, derived from a nonrandomized registry, provide a biological and clinical rationale for further prospective validation.

Growth curves for subcutaneous UOK360 tumor-bearing mice treated with vehicle or erlotinib.

Individual tumor growth curves.

Representative images of stained colony assays.

10x images of FH-RCC1X and RMC32X tissues stained with Ki67, CD34 and CD31.

Adjusted p-values between different treatment cohorts in RMC32X mice after 24 days of treatment and in FH-RCC1X mice after 30 days of treatment.

STR of original and patient tissue and preclinical models of FH-RCC1X and RMC32X.

Renal medullary carcinoma (RMC) and fumarate hydratase (FH)–deficient renal cell carcinoma (RCC) are rare and highly aggressive cancers. Although the combination of VEGF inhibition by bevacizumab and EGFR inhibition by erlotinib is clinically used for both diseases, the differential effect of each component has not been investigated. Transcriptomic profiling revealed that RMC and FH-deficient tumor tissues demonstrate increased EGFR but not VEGF expression compared with adjacent normal kidney. Subsequent in vitro studies revealed that RMC and FH-deficient cell lines are sensitive to erlotinib treatment, whereas clear-cell RCC cell lines are resistant. We developed patient-derived xenograft (PDX) models of tumors exposed to first-line therapies to represent treatment-experienced RMC and FH-deficient RCC models. These models were then used to determine tumor growth response to angiogenesis inhibition by bevacizumab alone or in combination with erlotinib. The FH-deficient RCC PDX model responded to either bevacizumab or erlotinib alone or in combination, whereas the RMC PDX model responded only to erlotinib, consistent with clinical and preclinical data suggesting that RMC is refractory to angiogenesis inhibition. Statistically higher expression of EGFR was observed in the RMC PDX model compared with the FH-deficient model, whereas higher phosphorylated tyrosine-416 SRC expression was observed in the FH-deficient PDX model compared with the RMC model. Our preclinical data suggest that EGFR signaling differentially modulates tumor growth in RMC and FH-deficient RCC and that angiogenesis inhibition is a valid target in FH-deficient RCC but not RMC.

Supplementary Table S3 lists the baseline demographics, clinical and prior treatment characteristics of the prospective RMC cohort used in the study.