Bromodomain-Containing Protein 4 (BRD4) Inhibition Sensitizes Palomid 529-Induced Anti-Renal Cell Carcinoma Cell Activity in Vitro and in Vivo

Abstract

Background/Aims: Mammalian target of rapamycin (mTOR) is a valuable treatment target of renal cell carcinoma (RCC). Palomid 529 is a novel mTORC1/2 dual inhibitor. Methods: RCC cells were treated with different concentrations of Palomid 529. Cell survival was tested by MTT assay and clonogenicity assay. Cell proliferation was tested by BrdU ELISA assay. Cell apoptosis was tested by the Hoechst-33342 nuclei staining assay and Histone DNA ELISA assay. mTOR signaling was tested by Western blotting assay and co-immunoprecipitation (IP) assay. The SCID mouse 786-O xenograft model was established to test RCC cell growth in vivo. Results: Palomid 529 exerted cytotoxic, anti-proliferative and pro-apoptotic activities in 786-O RCC cells. Palomid 529 disassembled mTORC1/2, causing de-phosphorylation of mTORC1/2 substrates. Bromodomain-containing protein 4 (BRD4) is a primary resistant factor of Palomid 529. Palomid 529-induced 786-O cell apoptosis was sensitized by BRD4 inhibitors or BRD4 silencing, but inhibited with BRD4 over-expression. Palomid 529-induced cytotoxicity in the primary human RCC cells was negatively correlated with BRD4 expression level. In vivo, Palomid 529 i.p. administration inhibited 786-O xenograft tumor growth in SCID mice. Its anti-tumor activity was further sensitized by co-administration of the BRD4 inhibitor JQ1. Cconclusion: Palomid 529 inhibits RCC cell growth in vitro and in vivo. BRD4 inhibition could further sensitize Palomid 529 against RCC cells.

Exploring synthetic lethal network for the precision treatment of clear cell renal cell carcinoma

“…The up-regulation of BRD4 expression was found in RCC tissues, and associated with advanced histological stage and lymph node metastasis, while knockdown of BRD4 reduced cell vitality and inhibited tumor growth 37 . The BRD4 inhibitor JQ-1 enhanced the anti-tumor activity of the mTOR inhibitor Palomid 529 in RCC cells 38 . Malignant peripheral nerve sheath tumor with PRC2 loss-of-function was sensitive to BRD4 inhibitor, suggesting a promising therapeutic approach of SL-based BRD4 inhibition 39 .…”

BRDT is a novel regulator of eIF4EBP1 in renal cell carcinoma

“…Hence, PLX51107 and INCB054329 is thought to inhibit tumor progression during specific conditions ( 49 – 51 ). Suppression of c-Myc transcription was hypothesized to serve an important role in BRD4-induced suppression of tumor growth in malignant hematological diseases and solid tumors ( 52 – 54 ). In lung cancer, the BET inhibitor JQ1 demonstrated antitumor functions not only via suppression of c-myc, but also via downregulation of FOSL1 ( 55 ).…”

The mitochondrial protein YME1 Like 1 is important for non-small cell lung cancer cell growth

“…CCK-8 cell viability, colony formation, the nuclear EdU/DAPI staining assay of cell proliferation, the caspase-3 activity assay, cell apoptosis detection by nuclear TUNEL/Hoechst 33342 staining, in vitro cell migration “Transwell” assays, JC-1 staining of mitochondrial depolarization were described in detail in our previous studies 30 , 31 . Trypan blue staining of cell death and ssDNA (single strand DNA) ELISA (Merck, Shanghai, China) were described in a previous study 35 , with the Histone-bound DNA ELISA assays described in another study 36 . Quantitative real time-PCR (qPCR), Western blotting and co-immunoprecipitation (Co-IP) was described early as well 30 , 31 .…”