GPNMB expression identifies TSC1/2/mTOR‐associated and MiT family translocation‐driven renal neoplasms

Abstract

GPNMB (glycoprotein nonmetastatic B) and other TFE3/TFEB transcriptional targets have been proposed as markers for microphthalmia (MiT) translocation renal cell carcinomas (tRCCs). We recently demonstrated that constitutive mTORC1 activation via TSC1/2 loss leads to increased activity of TFE3/TFEB, suggesting that the pathogenesis and molecular markers for tRCCs and TSC1/2-associated tumors may be overlapping. We examined GPNMB expression in human kidney and angiomyolipoma (AML) cell lines with TSC2 and/or TFE3/TFEB loss produced using CRISPR-Cas9 genome editing as well as in a mouse model of Tsc2 inactivation-driven renal tumorigenesis. Using an automated immunohistochemistry (IHC) assay for GPNMB, digital image analysis was employed to quantitatively score expression in clear cell RCC (ccRCC, n = 87), papillary RCC (papRCC, n = 53), chromophobe RCC (chRCC, n = 34), oncocytoma (n = 4), TFE3-or TFEB-driven tRCC (n = 56), eosinophilic solid and cystic RCC (ESC, n = 6), eosinophilic vacuolated tumor (EVT, n = 4), and low-grade oncocytic tumor (LOT, n = 3), as well as AML (n = 29) and perivascular epithelioid cell tumors (PEComas, n = 8). In cell lines, GPNMB was upregulated following TSC2 loss in a MiT/TFE-and mTORC1-dependent fashion. Renal tumors in Tsc2 +/À A/J mice showed upregulation of GPNMB compared with normal kidney. Mean GPNMB expression was significantly higher in tRCC than in ccRCC (p < 0.0001), papRCC (p < 0.0001), and chRCC (p < 0.0001). GPNMB expression in TSC1/2/MTOR alteration-associated renal tumors (including ESC, LOT, AML, and PEComa) was comparable to that in tRCC. The immunophenotype of tRCC and TSC1/2/MTOR alteration-associated renal tumors is highly overlapping, likely due to the increased activity of TFE3/TFEB in both, revealing an important caveat regarding the use of TFE3/TFEB-transcriptional targets as diagnostic markers.

Xanthomatous Giant Cell Renal Cell Carcinoma

“…We note that cathepsin K immunoreactivity is common to both TSC/mTOR pathway neoplasia and MiT-family renal cell carcinomas,30 as is immunoreactivity for GPNMB 31,32. This is consistent with recent molecular data which highlight that activation of mTOR pathway upregulates TFE3/TFEB expression in vitro, which promotes autophagy 32. In addition, the predominance of multinucleate tumor giant cells with eosinophilic cytoplasm also suggested epithelioid angiomyolipoma, which was excluded by the absence of immunoreactivity for melanocytic markers HMB45 and Melan A in both cases.…”

“…In both cases, absence of TFE3 or TFEB gene rearrangements helped exclude this possibility. We note that cathepsin K immunoreactivity is common to both TSC/mTOR pathway neoplasia and MiT-family renal cell carcinomas,30 as is immunoreactivity for GPNMB 31,32. This is consistent with recent molecular data which highlight that activation of mTOR pathway upregulates TFE3/TFEB expression in vitro, which promotes autophagy 32.…”

TFEB and TFE3 drive kidney cystogenesis and tumorigenesis

“…Therefore, BHD renal tumor cells, similar to other MiT/TFE ‐dependent cancer cells, may have acquired mechanisms to escape the negative regulation of mTORC1 signaling over the autophagy process to maximize nutrient scavenging pathways for the de novo synthesis of the macromolecules required for cancer proliferation and growth (Perera et al , 2019 ; Napolitano et al , 2022 ). Moreover, among our selected list of candidate genes responsible of tumor growth in BHD, we also find the protumorigenic protein GPNMB, a transmembrane protein highly enriched at the plasma membrane of different types of cancer cells (e.g., melanoma, glioblastoma, and breast cancer) whose upregulation has already been reported in BHD‐RCC (Hong et al , 2010 ; Furuya et al , 2015 ), but also in translocation (t)‐RCC (Baba et al , 2019 ), MITF‐RCC (Lang et al , 2021 ) and TSC‐renal tumors (Taya & Hammes, 2018 ; Salles et al , 2022 ). To start assessing the potential contribution of these 28 TFEB/TFE3 target genes to the BHD renal phenotype, we downregulated each of them in UOK257 cells and then monitored cell proliferation through MTT assay.…”

Renal Neoplasia Occurring in Patients With PTEN Hamartoma Tumor Syndrome

“…This finding in the kidney typically represents “lipid-rich” AML but the findings in this clinical scenario support a true adipocytic proliferation (ie, “lipoma”), supported by immunoreactivity for cathepsin-K and GPNMB. GPNMB has been reported as a highly sensitive marker of TSC1/TSC2/MTOR-driven renal neoplasms 36 . The distinction from AML is important since the presence of chromophobe RCC and multiple microscopic AMLs would raise suspicion for underlying tuberous sclerosis complex.…”

“…GPNMB has been reported as a highly sensitive marker of TSC1/TSC2/ MTOR-driven renal neoplasms. 36 The distinction from AML is important since the presence of chromophobe RCC and multiple microscopic AMLs would raise suspicion for underlying tuberous sclerosis complex. With careful morphologic assessment, many lipid-rich AMLs have a distinct population of epithelioid or spindled PE-Coma cells without intracytoplasmic lipid, making diagnosis straightforward.…”