KIX domain determines a selective tumor-promoting role for EP300 and its vulnerability in small cell lung cancer

Abstract

EP300, a transcription coactivator important in proliferation and differentiation, is frequently mutated in diverse cancer types, including small cell lung cancer (SCLC). While these mutations are thought to result in loss of EP300 function, the impact on tumorigenesis remains largely unknown. Here, we demonstrate that EP300 mutants lacking acetyltransferase domain accelerate tumor development in mouse models of SCLC. However, unexpectedly, complete Ep300 knockout suppresses SCLC development and proliferation. Dissection of EP300 domains identified kinase inducible domain-interacting (KIX) domain, specifically its interaction with transcription factors including MYB, as the determinant of protumorigenic activity. Ala 627 in EP300 KIX results in a higher protein-binding affinity than Asp 647 at the equivalent position in CREBBP KIX, underlying the selectivity of KIX-binding partners for EP300. Blockade of KIX-mediated interactions inhibits SCLC development in mice and cell growth. This study unravels domain-specific roles for EP300 in SCLC and unique vulnerability of the EP300 KIX domain for therapeutic intervention.

Rapid-kinetics degron benchmarking reveals off-target activities and mixed agonism-antagonism of MYB inhibitors

“…The KIX domain of p300/CBP interacts with a number of other TFs 52 , and therefore the "off-target" effects of the KIX-binding inhibitors may in fact represent on-target modulation of p300/CBP in a MYB-independent manner. Conversely, while the interaction with p300/CBP is essential for the oncogenic properties of MYB 53,54 , it does not represent the full repertoire of MYB interactions 22,30,55,56 , and any p300/CBP-independent activities of MYB will be preserved after p300/CBP inhibition.…”

CRACD loss promotes small cell lung cancer tumorigenesis via EZH2-mediated immune evasion

“…Human embryonic kidney 293T (HEK293T) and NCI-H2081 used in this study were purchased from American Type Culture Collection (ATCC). The murine preSC cells have been previously described (Kim et al, 2016; Kim et al, 2022b). HEK293T and preSC cells were maintained in a Dulbecco’s Modified Eagle’s Medium (DMEM) medium containing 10% fetal bovine serum (Thermo Fisher Scientific) and 1% penicillin and streptomycin (Thermo Fisher Scientific).…”

“…Immunocompromised (BALB/c athymic nude) mice and C57BL/6 mice were purchased from the Jackson Laboratory (Maine, USA). Compound transgenic mice Rb1 lox/lox Trp53 lox/lox Rbl2 lox/lox (RPR2) mice have been previously described (Kim et al, 2022b). For SCLC tumor induction, the lungs of 10-week-old mice were infected with adenoviral Cre via intratracheal instillation as previously described (DuPage et al, 2009; Kim et al, 2022b).…”

“…Compound transgenic mice Rb1 lox/lox Trp53 lox/lox Rbl2 lox/lox (RPR2) mice have been previously described (Kim et al, 2022b). For SCLC tumor induction, the lungs of 10-week-old mice were infected with adenoviral Cre via intratracheal instillation as previously described (DuPage et al, 2009; Kim et al, 2022b). Multiple cohorts of independent litters were analyzed to control for background effects, and both male and female mice were used.…”

The New Way to Define Key Oncogenic Drivers of Small Cell Lung Cancer

“…Recent studies present a 2-step approach for testing the disease relevance of uncharacterized somatic alterations found in SCLC. First, in an in vitro model, we induce candidate mutations in pre-cancerous cells (preSC) derived from the GEMM and characterize cellular phenotypes for transformation (Kim et al, 2016;Jia et al, 2018;Kim et al, 2020;Kim et al, 2022a). Second, we suggest in an in vivo model where we induce the in vitro prioritized mutations in the GEMM, using adenoviral delivery of clustered regularly interspaced short palindromic repeats (CRISPR)-Cre hybrid system (Kim et al, 2022b).…”