POU2F3 expression

This study confirmed the SCLC subtyping based on key transcription factors. While no significant differences in OS and PFS among subtypes were found, the SCLC-I subtype showed potential benefit from platinum-based chemotherapy combined with immune checkpoint inhibitors. M stage and bone metastasis at diagnosis were identified as independent risk factors for SCLC.

SCLCs were found to have relatively colder immune profiles than lung adenocarcinomas and squamous cell carcinomas, characterized by lower expression of HLA genes, immune cell, and immune checkpoint genes, except the LAG3 gene. Clinical-grade SCLC RNA expression profiling has value for SCLC subtyping, design of clinical trials, and identification of patients for trials and potential targeted therapy.

POU2F3 expression is a highly sensitive but nonspecific indicator of tuft cell differentiation. Co-expression of POU2F3 and POU2AF2 appears to be a more specific marker, although it may not pinpoint tumors driven by the POU2F3-POU2AF3 complex.

POU2F3-positive SCBC showed higher expression levels of POU2F3, HMGA2 and PLCG2 genes by RNA-Seq. Our data showed the specific clinicopathologic features of 4 rare POU2F3-positive SCBC cases, and the distinct molecular feature was observed between POU2F3-positive and negative SCBC in the limited number of cases.

The presence of POU2F3-expressing cells in normal urothelium, cystitis cystica glandularis and IM of the urinary bladder is demonstrated in separate cases of cystitis cystica glandularis with IM. Also, POU2F3 expression is identified in a subset of bladder SmCC.

The expression patterns of the characteristic transcription factors found in ionocytes and tuft cells vary among salivary gland tumor types and are higher in WT, which might be relevant for understanding and diagnosing salivary gland neoplasms.

AURKA and FGFR2 are both possible targets for inhibition in SCLC and LCNEC, but patients' selection should be based on expression of the enzyme. Combined chemo- and immunotherapy might be decided by PD-L1 staining of stroma cells.

Recognition of this unique subtype may provide clues for solving the long-standing issues of NEC and appropriate therapeutic stratification. It is important to accurately identify POU2F3-expressing carcinomas by immunohistochemistry and to analyze their clinicopathological features.

YAP1 upregulated PD-L1 expression and suppressed T cell activation, thus leading to immune evasion. In in vitro experiments, blockade of YAP1 promoted cancer cell apoptosis, immune cell proliferation, T-cell activation, and cytotoxic T-cell infiltration, thus further potentiating the efficacy of immunotherapy in patients with the SCLC-Y subtype.

Plasticity was observed with rare cases switching from NEUROD1-predominant to ASC1-predominant SCLC. Resubtyping is unnecessary for the consideration of novel subtype-specific targeted agents, except cases with NEUROD1-predominant subtype.

One case of esophageal NE tumor was nuclear-positive, while the normal proliferating squamous epithelium was strongly membrane-stained. This is the largest cohort of clinical samples to confirm that POU2F3 is a highly sensitive and specific diagnostic marker for NE-low/negative SCLC.

We further highlight the promising immunotherapy strategies in SCLC that are currently under investigation. PRACTICAL APPLICATIONS: Recent biological findings push toward a future morphomolecular classification, although they have not yet fully translated into novel therapeutic options for all subtypes.The optimal systemic treatment for patients with stage IV large-cell neuroendocrine carcinoma is yet to be defined, with both small-cell lung carcinoma (SCLC) and non–small-cell lung carcinoma systemic therapy regimens commonly used in practice.Biologic subtypes are classified by differential expression of transcription regulators, such as ASCL1 (achaete-scute homolog 1), NEUROD1 (neurogenic differentiation factor 1), and POU2F3 (POU class 2 homeobox 3), or low expression of all three transcription factor signatures accompanied by an inflamed gene signature and may have therapeutic implications.Combined PD-L1 inhibitors and platinum-doublet chemotherapy improve overall survival in all patients with extensive-stage SCLC and may preferentially benefit patients with the SCLC-I subtype.Bispecific T-cell engagers and chimeric antigen receptor T cells designed against unique SCLC tumor antigens, such as DLL3, are novel immunotherapeutic strategies to overcome deficiencies in antigen presentation, which are common in SCLC.

POU2F3 expression defines small subsets in various breast cancer subtypes, which can be accompanied by DCIS. The mechanistic relationship between POU2F3 and SOX9 in the breast warrants further analysis to enhance our understanding of normal breast physiology and to clarify the significance of the tuft cell-like phenotype for TNBCs.

The positivity for these markers in TMAs and LN metastatic sites was significantly correlated with that of corresponding surgical specimens, indicating that biopsy specimens could be used to identify molecular subtypes of SCLC in patients.

The aim of this study was to analyze the activity of lurbinectedin in the different SCLC molecular subtypes and to investigate new biomarkers of response.Methods and Results - We have characterized a panel of 20 SCLC human cell lines based on the expression of ASCL1, NEUROD1, YAP1 and POU2F3, where lurbinectedin yielded a mean IC50 value of 6.52 nM, which is considerable greater than the activity exerted by topotecan, irinotecan, carboplatin, etoposide, olaparib, alisertib and navitoclax (IC50 100 µM-100 nM). Finally, SLFN11 expression was evaluated by IHC in FFPE tumor samples from SCLC patients participating in a multicenter phase II clinical trial in advanced solid tumors (NCT02454972), which allowed lurbinectedin accelerated approval in this indication by FDA. Patients with higher expression of SLFN11 had a slightly better overall survival (OS at 6 months: 68.4% (<15%, N=20) vs. 98.7% (≥15%, N=20) p=0.0261)), especially in the refractory/resistant subgroup (OS at 6 months: 33.3% (<15%, N=9) vs. 100.0% (≥15%, N=6) p<0.0001).Conclusions - Lurbinectedin is highly effective in all molecular subtypes of SCLC in vitro and in vivo, with IC50 values at least two logs more potent than for other antitumoral agents and its activity is even greater in tumors with high POU2F3 expression and/or high SLFN11 expression.

However, the interaction between the tuft cells and cancer remains to be further elucidated. Here, based on an introduction of biological functions and specific markers of the tuft cells, we have summarized the functional roles and potential therapeutic implications of tuft cells in cancers, including pancreatic cancer, lung cancer, gastric cancer, colon cancer, and liver cancer, which is in the hope of inspiring the future research in validating tuft cells as novel strategies for cancer therapies.

Taken together, pulmonary tuft cell-like cancers maintain histotype-related clinicopathologic characteristics despite overlapping unique molecular features. From a therapeutic perspective, identification of tuft cell-like LCNECs might be crucial given their close kinship with tuft cell-like SCLC.

We found rare extrapulmonary POU2F3-positive tumors arising from previously unappreciated cells of origin. Our data show novel molecular pathologic features of EP-NEC/PDCs including potential therapeutic vulnerabilities, thereby emphasizing the need for focusing on unique features of EP-NEC/PDCs.

On the basis of the molecular function of C11orf53, we renamed it as "POU Class 2 Homeobox Associating Factor 2" (POU2AF2). In summary, our study has identified a new coactivator of POU2F3 and sheds light on the therapeutic potential of targeting POU2AF2/POU2F3 heterodimer in human SCLC.

This is the largest cohort of SCLC-P clinical samples to date, where we describe the diagnostic utility of POU2F3 in a challenging subset of SCLC with low or absent expression of standard neuroendocrine markers. The distinct genomic alterations in SCLC-P may offer a novel avenue for therapeutic targeting. The role of POU2F3 in a narrow subset of other lung cancer types warrants further study.

None of the genes was correlated with any specific genotype. Conclusion Our data show that: i) ADC-NED are associated with specific profiles of transcriptional regulation; ii) the expression of these genes is influenced by the tumor genotype; iii) the association of some of these genes with clinical and pathological features support their potential role as novel biomarkers.

High POU2F3 expression is associated with improved survival in a univariate analysis, whereas elevated ASCL1 expression is an independent negative prognosticator. Proteomic and cell viability assays of human SCLC cell lines reveal distinct vulnerability profiles defined by transcription regulators.

In our experiments, high mRNA expression of POU2F3 in SCLC cell lines correlated with the effect of lurbinectedin.