Fig 2: The POU2F3 transcription factor complex is evicted from chromatin in SCLC-P cells upon mSWI/SNF ATPase degradation(A) Visualization of ATAC-seq read-density in NCI-H526 (SCLC-P) and NCI-H69 (SCLC-A) cells post-treatment for 4 h with either vehicle or 1 μM AU-15330 (n =2 biological replicates).(B) Analysis of fold change and significance level for HOMER motifs that are enriched within sites dependent and independent of the mSWI/SNF complex in NCI-H526 and NCI-H69 cells.(C) ChIP-seq read-density heatmaps representing POU2F3 (green), HA-POU2F3 (red), and HA-POU2AF2 (blue) at AU-15330-loss genomic sites in NCI-H526 cells following treatment with DMSO or AU-15330.(D) Volcano plot detailing proteins that interact with POU2AF2, as identified by POU2AF2 RIME analysis in NCI-H526 cells. mSWI/SNF components highlighted in orange (n = 3 biological replicates).(E) Expression levels of POU2F3, POU2AF2/3, and PTGS1 as assessed by QPCR (normalized to ACTB) in the indicated cell lines after being treated for 12 h with vehicle or 1 μM AU-15330. Data are presented as mean ± SD (n = 3 biological replicates).(F) Volcano plot visualizing the overall transcriptomic alterations as assessed by RNA-seq in NCI-H526 and NCI-H1048 cells post-treatment for 12 h with vehicle or 1 μM AU-15330. Canonical POU2F3 target genes are highlighted in blue (n = 2 biological replicates).(G) GSEA plots illustrating genes regulated by POU2F3 and its coactivators POU2AF2 and POU2AF3. The plots employ a gene signature ranked by fold change in AU-15330-treated NCI-H526 and NCI-1048 cells. DEG, differentially expressed gene.(H) Combined ATAC-seq and ChIP-seq tracks for AVIL, PTGS1, and ASCL2 in NCI-H526 with and without AU-15330 treatment. See also Figures S1–S3 and Table S1.

Fig 3: Selective inhibition of SCLC-P xenograft tumor models employing an orally bioavailable mSWI/SNF ATPase degrader(A) Overview of the AU-24118 efficacy study conducted using SCLC xenograft models.(B) Analysis of tumor volume in indicated SCLC xenograft models upon treatment with AU-24118, measured bi-weekly using calipers. Statistical analysis was performed using a two-way ANOVA. Data are presented as mean ± SEM.(C) Immunoblots illustrating levels of the indicated proteins in SCLC-P and SCLC-A xenografts after 5 days of AU-24118 administration. Vinculin is utilized as the loading control across immunoblots. CDX, cell line-derived xenograft.(D) Representative H&E staining with corresponding IHC analyses for SMARCA4, POU2F3, and DCLK1 after 5 days of treatment with AU-24118 in NCI-H526 xenografts (scale, 50 mm). The inset scale, 20 μm.(E) (left) Representative DAPI and TUNEL staining from xenografts from indicated cell lines after 5 days of AU-24118 treatment (scale, 100 μm). (right) Quantitative evaluation of TUNEL staining of respective SCLC xenografts for 5 days. t tests were used to calculate the significance. p value < 0.05 in the top panel. The whiskers extend from the minimum to the maximum values, indicating the full range of the data. The middle line represents the median of the data. The box spans from the first quartile (Q1, 25th percentile) to the third quartile (Q3, 75th percentile), representing the interquartile range (IQR).(F) Analysis of tumor volume in Lx1322 patient-derived xenograft (PDX) model upon treatment with AU-24118, measured bi-weekly using calipers. Statistical analysis was performed using a two-way ANOVA. Data are presented as mean ± SEM.(G) Representative H&E staining with corresponding IHC analyses for SMARCA4 after 5 days of treatment with AU-24118 in Lx1322 PDX (scale, 50 mm). The inset scale, 20 μm.(H) DCLK1 cell positivity in lung and small intestine for endpoint evaluation. AU-24118 (15 mg/kg) dosed. Ns, not significant (t tests). The whiskers extend from the minimum to the maximum values, indicating the full range of the data. The middle line represents the median of the data. The box spans from the first quartile (Q1, 25th percentile) to the third quartile (Q3, 75th percentile), representing the interquartile range (IQR).See also Figures S3 and S4.