Therapeutic Targeting of TFE3/IRS-1/PI3K/mTOR Axis in Translocation Renal Cell Carcinoma

Nur P Damayanti, Justin A Budka, Heba W Z Khella, Mary W Ferris, Sheng Yu Ku, Eric Kauffman, Anthony C Wood, Khunsha Ahmed, Venkata Nithinsai Chintala, Remi Adelaiye-Ogala, May Elbanna, Ashley Orillion, Sreenivasulu Chintala, Chinghai Kao, W Marston Linehan, George M Yousef, Peter C Hollenhorst, Roberto Pili
Clinical Cancer Research 2018 December 1, 24 (23): 5977-5989

PURPOSE: Translocation renal cell carcinoma (tRCC) represents a rare subtype of kidney cancer associated with various TFE3, TFEB , or MITF gene fusions that are not responsive to standard treatments for RCC. Therefore, the identification of new therapeutic targets represents an unmet need for this disease.

EXPERIMENTAL DESIGN: We have established and characterized a tRCC patient-derived xenograft, RP-R07, as a novel preclinical model for drug development by using next-generation sequencing and bioinformatics analysis. We then assessed the therapeutic potential of inhibiting the identified pathway using in vitro and in vivo models.

RESULTS: The presence of a SFPQ-TFE3 fusion [t(X;1) (p11.2; p34)] with chromosomal break-points was identified by RNA-seq and validated by RT-PCR. TFE3 chromatin immunoprecipitation followed by deep sequencing analysis indicated a strong enrichment for the PI3K/AKT/mTOR pathway. Consistently, miRNA microarray analysis also identified PI3K/AKT/mTOR as a highly enriched pathway in RP-R07. Upregulation of PI3/AKT/mTOR pathway in additional TFE3-tRCC models was confirmed by significantly higher expression of phospho-S6 ( P < 0.0001) and phospho-4EBP1 ( P < 0.0001) in established tRCC cell lines compared with clear cell RCC cells. Simultaneous vertical targeting of both PI3K/AKT and mTOR axis provided a greater antiproliferative effect both in vitro ( P < 0.0001) and in vivo ( P < 0.01) compared with single-node inhibition. Knockdown of TFE3 in RP-R07 resulted in decreased expression of IRS-1 and inhibited cell proliferation.

CONCLUSIONS: These results identify TFE3/IRS-1/PI3K/AKT/mTOR as a potential dysregulated pathway in TFE3-tRCC, and suggest a therapeutic potential of vertical inhibition of this axis by using a dual PI3K/mTOR inhibitor for patients with TFE3-tRCC.


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