Transforming growth factor beta (TGFβ) and activin A suppress natural killer (NK) cell function and proliferation, limiting the efficacy of adoptive NK cell therapies. Inspired by the partial resistance to TGFβ of NK cells with SMAD4 haploinsufficiency, we used CRISPR–Cas9 for knockout of SMAD4 in human NK cells. Here we show that SMAD4^KO NK cells were resistant to TGFβ and activin A inhibition, retaining their cytotoxicity, cytokine secretion and interleukin-2/interleukin-15-driven proliferation. They showed enhanced tumor penetration and tumor growth control, both as monotherapy and in combination with tumor-targeted therapeutic antibodies. Notably, SMAD4^KO NK cells outperformed control NK cells treated with a TGFβ inhibitor, underscoring the benefit of maintaining SMAD4-independent TGFβ signaling. SMAD4^KO conferred TGFβ resistance across diverse NK cell platforms, including CD19-CAR NK cells, stem cell-derived NK cells and ADAPT-NK cells. These findings position SMAD4 knockout as a versatile and compelling strategy to enhance NK cell antitumor activity, providing a new avenue for improving NK cell-based cancer immunotherapies.

Immune checkpoint inhibitors (ICIs) targeting the programmed cell death protein 1 (PD‐1)/programmed cell death 1 ligand 1 (PD‐L1) pathway have transformed urothelial cancer (UC) therapy. The correlation between PD‐L1 expression and ICI effectiveness is uncertain, leaving the role of PD‐L1 as a predictive marker for ICI efficacy unclear. Among several ways to enhance the efficacy of ICI, trials are exploring combining ICIs with serine/threonine‐protein kinase mTOR (mTOR) inhibitors in different tumor types. The potential interaction between mTOR inhibitors and PD‐L1 expression in UC has not been well characterized. In our study, we investigated how phosphoinositide 3‐kinase (PI3K)/AKT/mTOR pathway inhibitors (TAK‐228, everolimus and TAK‐117) affect PD‐L1 expression and function in preclinical bladder cancer cell models. TAK‐228 increased cell surface levels of glycosylated PD‐L1 in all but one of the seven cell lines, regardless of baseline levels. TAK‐228 promoted the secretion of epidermal growth factor (EGF) and interferon‐β (IFNβ), both linked to PD‐L1 protein induction. Blocking EGF and IFNβ receptors reversed the TAK‐228‐induced PD‐L1 increase. Additionally, TAK‐228 enhanced IFN‐γ‐induced PD‐L1 expression and intracellular HLA‐I levels in some cells. TAK‐228‐treated bladder cancer cells exhibited resistance to the cytotoxic effects of peripheral blood mononuclear cells (PBMCs) and cluster of differentiation 8 (CD8)+ T cells. The addition of an anti‐PD‐L1 antibody diminished this resistance in T24 cells. Increased expression of PD‐L1 under TAK‐228 exposure was confirmed in patient‐derived explants (PDEs) treated ex vivo. These preclinical findings suggest that mTOR inhibition with TAK‐228 can increase PD‐L1 levels, potentially impacting the specific immune response against UC cells. This highlights the rationale for exploring the combination of mTOR inhibitors with ICIs in patients with advanced UC.

Complex RNA-seq signatures involving the transcription factors ASCL1, NEUROD1, and POU2F3 classify Small Cell Lung Cancer (SCLC) into four subtypes: SCLC-A, SCLC-N, SCLC-P, and SCLC-I (triple negative or inflamed). Preliminary studies suggest that identifying these subtypes can guide targeted therapies and potentially improve outcomes. This study aims to evaluate whether the expression levels of these three key transcription factors can effectively classify SCLC subtypes, comparable to the use of individual antibodies in immunohistochemical (IHC) analysis of formalin-fixed, paraffin-embedded (FFPE) tumor samples. We analyzed preclinical models of increasing complexity, including eleven human and five mouse SCLC cell lines, six patient-derived xenografts (PDXs), and two circulating tumor cell (CTC)-derived xenografts (CDXs) generated in our laboratory. RT-qPCR conditions were established to detect the expression levels of ASCL1, NEUROD1, and POU2F3. Additionally, protein-level analysis was performed using Western blot for cell lines and IHC for FFPE samples of PDX and CDX tumors, following our experience with patient tumor samples from the CANTABRICO trial (NCT04712903). We found that the analyzed SCLC cell line models predominantly expressed ASCL1, NEUROD1, and POU2F3, or showed no expression, as identified by RT-qPCR, consistently matching the previously assigned subtypes for each cell line. The classification of PDX and CDX models demonstrated consistency between RT-qPCR and IHC analyses of the transcription factors. Our results show that single-gene analysis by RT-qPCR from FFPE-extracted RNA simplifies SCLC subtype classification. This approach provides a cost-effective alternative to IHC staining or expensive multi-gene RNA sequencing panels, making SCLC subtyping more accessible for both preclinical research and clinical applications.