Notch signaling triggers the tumor heterogeneity of small cell lung cancer

Combined small cell lung cancer: current progress and unmet needs

Combined small cell lung cancer (CSCLC) is a specific subtype of lung cancer characterized by a pathological mixture of small cell lung cancer and any subtype of non-small cell lung cancer components. Currently, our understanding of the clinicopathological features, origin, molecular characterization, treatment, and prognosis of CSCLC remains limited. CSCLCs represent examples of intratumor heterogeneity and pose challenges for accurate diagnosis. Are there any distinct clinicopathologic and molecular differences between pure SCLC and CSCLC? Furthermore, the prognostic outcomes and optimal treatments for CSCLC are urgently needed. This article aims to summarize the current biological features and clinical management of CSCLC, providing a reference for further understanding of this heterogeneous form of small cell lung cancer.

Integrative molecular analysis of combined small-cell lung carcinomas identifies major subtypes with different therapeutic opportunities

BACKGROUND

Combined small-cell lung cancer (C-SCLC) is composed of SCLC admixed with a non-small-cell cancer component. They currently receive the same treatment as SCLC. The recent evidence that SCLC may belong to either of two lineages, neuroendocrine (NE) or non-NE, with different vulnerability to specific cell death pathways such as ferroptosis, opens new therapeutic opportunities also for C-SCLC.

MATERIALS AND METHODS

Thirteen C-SCLCs, including five with adenocarcinoma (CoADC), five with large-cell neuroendocrine carcinoma (CoLCNEC) and three with squamous cell carcinoma (CoSQC) components, were assessed for alterations in 409 genes and transcriptomic profiling of 20 815 genes.

RESULTS

All 13 cases harbored TP53 (12 cases) and/or RB1 (7 cases) inactivation, which was accompanied by mutated KRAS in 4 and PTEN in 3 cases. Potentially targetable alterations included two KRAS G12C, two PIK3CA and one EGFR mutations. Comparison of C-SCLC transcriptomes with those of 57 pure histology lung cancers (17 ADCs, 20 SQCs, 11 LCNECs, 9 SCLCs) showed that CoLCNEC and CoADC constituted a standalone group of NE tumors, while CoSQC transcriptional setup was overlapping that of pure SQC. Using transcriptional signatures of NE versus non-NE SCLC as classifier, CoLCNEC was clearly NE while CoSQC was strongly non-NE and CoADC exhibited a heterogeneous phenotype. Similarly, using ferroptosis sensitivity/resistance markers, CoSQC was classified as sensitive (as expected for non-NE), CoLCNEC as resistant (as expected for NE) and CoADC showed a heterogeneous pattern.

CONCLUSIONS

These data support routine molecular profiling of C-SCLC to search for targetable driver alterations and to precisely classify them according to therapeutically relevant subgroups (e.g. NE versus non-NE).

Molecular profiles of small cell lung cancer subtypes: therapeutic implications

Small cell lung cancer (SCLC; accounting for approximately 13%-15% of all lung cancers) is an exceptionally lethal malignancy characterized by rapid doubling time and high propensity to metastasize. In contrast to the increasingly personalized therapies in other types of lung cancer, SCLC is still regarded as a homogeneous disease and the prognosis of SCLC patients remains poor. Recently, however, substantial progress has been made in our understanding of SCLC biology. Advances in genomics and development of new preclinical models have facilitated insights into the intratumoral heterogeneity and specific genetic alterations of this disease. This worldwide resurgence of studies on SCLC has ultimately led to the development of novel subtype-specific classifications primarily based on the neuroendocrine features and distinct molecular profiles of SCLC. Importantly, these biologically distinct subtypes might define unique therapeutic vulnerabilities. Herein, we summarize the current knowledge on the molecular profiles of SCLC subtypes with a focus on their potential clinical implications.

Notch pathway in small-cell lung cancer: from preclinical evidence to therapeutic challenges

BACKGROUND

Small-cell lung cancer (SCLC) is an aggressive disease with still limited therapeutic options. Despite being both a chemo- and radiation-sensitive malignancy, SCLC recurrence occurs in most cases and negatively impacts patients' prognosis. Over the last few years, a deeper understanding of SCLC molecular aberrations has led to the identification of Notch pathway deregulation as a crucial event in SCLC tumorigenesis, disease progression and chemoresistance. In particular, the delta-like protein 3 (DLL3), a Notch inhibitory ligand whose expression is directly related to the key neuroendocrine transcription factor ASCL1, was found to be expressed in ~85% of SCLCs, while it exhibits minimal to absent surface expression in normal lungs. DLL3 thus represents an appealing novel biomarker as well as a potential target in SCLC.

CONCLUSIONS

The first DLL3-targeted antibody-drug conjugate rovalpituzumab tesirine (Rova-T, SC16LD6.5) has shown promising results in terms of efficacy and safety for the management of extensive SCLC, supporting further studies on this novel therapeutic approach that combines specific SCLC targeting with the cell-killing ability of a pyrrolobenzodiazepine dimer. In the present review, we discuss currently available evidence on the biological role of Notch signaling in SCLC from early preclinical findings to current and future clinical implications.

Elevated Notch1 enhances interleukin-22 production by CD4+ T cells via aryl hydrocarbon receptor in patients with lung adenocarcinoma

Notch signaling induced interleukin (IL)-22 secretion by CD4+ T cells via retinoid-related orphan nuclear receptor γt (RORγt) or aryl hydrocarbon receptor (AhR). Previous studies have demonstrated that Notch-AhR-IL-22 axis took part in the pathogenesis of chronic viral infection, however, its role in cancer has not been fully elucidated. Thus, the aim of current study was to investigate the involvement of Notch-AhR-IL-22 axis in the pathogenesis of lung adenocarcinoma. A total of 37 late-stage lung adenocarcinoma patients and 17 healthy individuals were enrolled. CD4+ T cells were purified from peripheral bloods and bronchoalveolar lavage fluids (BALF), and were stimulated with γ-secretase inhibitor (GSI). mRNA corresponding to Notch receptors and transcriptional factors were measured by real-time PCR. IL-22 concentration was investigated by ELISA. The bioactivity (including cellular proliferation, cell cycle, apoptosis, and invasion) of lung adenocarcinoma cell line A549 was also assessed in response to recombinant IL-22 stimulation in vitro. Notch1 mRNA expression was significantly elevated in CD4+ T cells purified from peripheral bloods and tumor site BALF in lung adenocarcinoma patients. IL-22 expression and RORγt/AhR mRNA in BALF was also remarkably increased in tumor site. Inhibition of Notch signaling by GSI did not affect cellular proliferation, but reduced IL-22 production in CD4+ T cells from BALF, along with down-regulation of AhR, but not RORγt. Moreover, IL-22 stimulation promoted A549 cells invasion. The current data indicated that elevated Notch1 induced higher IL-22 secretion by CD4+ T cells in lung adenocarcinoma patients, and Notch-AhR-IL-22 axis took part in the pathogenesis of lung adenocarcinoma.

Lung cancer stem cells: origin, features, maintenance mechanisms and therapeutic targeting

Lung cancer remains the leading cause of cancer-related deaths despite recent breakthroughs in immunotherapy. The widely embraced cancer stem cell (CSC) theory has also been applied for lung cancer, postulating that an often small proportion of tumor cells with stem cell properties are responsible for tumor growth, therapeutic resistance and metastasis. The identification of these CSCs and underlying molecular maintenance mechanisms is considered to be absolutely necessary for developing therapies for their riddance, hence achieving remission. In this review, we will critically address the CSC concept in lung cancer and its advancement thus far. We will describe both normal lung stem cells and their malignant counterparts in order to identify common aspects with respect to their emergence and regulation. Subsequently, the importance of CSCs and their molecular features in lung cancers will be discussed in a preclinical and clinical context. We will highlight some examples on how lung CSCs attain stemness through different molecular modifications and cellular assistance from the tumor microenvironment. The exploitation of these mechanistic features for the development of pharmacological therapy will also be discussed. In summary, the validity of the CSC concept has been evidenced by various studies. Ongoing research to identify molecular mechanisms driving lung CSC have revealed potential new cell intrinsic as well as tumor microenvironment-derived therapeutic targets. Although successfully demonstrated in preclinical models, the clinical benefit of lung CSC targeted therapies has thus far not been demonstrated. Therefore, further research to validate the therapeutic value of CSC concept is required.