Pathway targets to explore in the treatment of small cell and large cell lung cancers

Comprehensive analysis of prognostic predictors for patients with limited-stage small-cell lung cancer who underwent resection followed by adjuvant chemotherapy

Background

The prognosis of patients with limited-stage small-cell lung cancer (LS-SCLC) who undergo resection followed by adjuvant chemotherapy (ACT) is uncertain. Thus, we combined clinicopathological characteristics and next-generation sequencing (NGS) to answer this question.

Methods

In total, the data of 51 LS-SCLC patients who had undergone complete surgical resection and postoperative ACT were retrospectively collected. NGS examinations with a 68-gene panel were performed for each specimen. Patients' genetic status and potentially clinical correlations were statistically evaluated. Progression-free survival (PFS) and overall survival (OS) were plotted using Kaplan-Meier curves. The independent prognostic factors for the primary cohort were investigated using univariable and multivariable cox proportional hazard regression analyses. Subgroup analyses were also conducted based on retinoblastoma protein 1 (RB1) status.

Results

Combined SCLC (c-SCLC) had similar clinical and pathological characteristics to that of pure SCLC (p-SCLC). TP53 and RB1 were 2 major genetic mutations present in both p-SCLC and c-SCLC. c-SCLC had a unique genetic profile that was related to the PI3K/AKT/mTOR and WNT/β-catenin signaling pathways. There was no prognostic difference between c-SCLC and p-SCLC. However, the pathological node (N) stage of lymphovascular invasion (LVI), which was related to PFS and age, corelated with OS. Neither pathological subtypes nor genetic mutations affected the survival outcomes. Notably, RB1 mutated c-SCLC resulted in poorer DFS compared to that of p-SCLC among LS-SCLC patients who underwent resection followed by ACT.

Conclusions

Our examination of LS-SCLC patients who underwent resection followed by ACT showed that c-SCLC and p-SCLC had a clinical and prognostic similarity and a genetic peculiarity. Thus, it is essential that a new classification system be proposed for SCLC. Such a system is especially needed for LS-SCLC.

NOTCH, ASCL1, p53 and RB alterations define an alternative pathway driving neuroendocrine and small cell lung carcinomas

Small cell lung cancers (SCLCs) and extrapulmonary small cell cancers (SCCs) are very aggressive tumors arising de novo as primary small cell cancer with characteristic genetic lesions in RB1 and TP53. Based on murine models, neuroendocrine stem cells of the terminal bronchioli have been postulated as the cellular origin of primary SCLC. However, both in lung and many other organs, combined small cell/non‐small cell tumors and secondary transitions from non‐small cell carcinomas upon cancer therapy to neuroendocrine and small cell tumors occur. We define features of “small cell‐ness” based on neuroendocrine markers, characteristic RB1 and TP53 mutations and small cell morphology. Furthermore, here we identify a pathway driving the pathogenesis of secondary SCLC involving inactivating NOTCH mutations, activation of the NOTCH target ASCL1 and canonical WNT‐signaling in the context of mutual bi‐allelic RB1 and TP53 lesions. Additionaly, we explored ASCL1 dependent RB inactivation by phosphorylation, which is reversible by CDK5 inhibition. We experimentally verify the NOTCH‐ASCL1‐RB‐p53 signaling axis in vitro and validate its activation by genetic alterations in vivo. We analyzed clinical tumor samples including SCLC, SCC and pulmonary large cell neuroendocrine carcinomas and adenocarcinomas using amplicon‐based Next Generation Sequencing, immunohistochemistry and fluorescence in situ hybridization. In conclusion, we identified a novel pathway underlying rare secondary SCLC which may drive small cell carcinomas in organs other than lung, as well.

What's new?

Using next generation sequencing and establishing features of ‘small cell‐ness’, we identified a NOTCH‐ASCL1‐RB1‐TP53 signaling axis driving small cell cancers. In contrast to the previously described bi‐allelic RB1/TP53 loss in neuroendocrine stem cells as origin of primary small cell neuroendocrine cancers, the NOTCH‐ASCL1 mediated signaling defines an alternative pathway driving secondary small cell neuroendocrine cancers arising from non‐small cell cancers. Moreover, we show a preclinical rational for therapeutically testing WNT‐inhibitors in small cell cancers.

Array-based pharmacogenomics of molecular-targeted therapies in oncology

The advent of microarrays over the past decade has transformed the way genome-wide studies are designed and conducted, leading to an unprecedented speed of acquisition and amount of new knowledge. Microarray data have led to the identification of molecular subclasses of solid tumors characterized by distinct oncogenic pathways, as well as the development of multigene prognostic or predictive models equivalent or superior to those of established clinical parameters. In the field of molecular-targeted therapy for cancer, in particular, the application of array-based methodologies has enabled the identification of molecular targets with 'key' roles in neoplastic transformation or tumor progression and the subsequent development of targeted agents, which are most likely to be active in the specific molecular setting. Herein, we present a summary of the main applications of whole-genome expression microarrays in the field of molecular-targeted therapies for solid tumors and we discuss their potential in the clinical setting. An emphasis is given on deciphering the molecular mechanisms of drug action, identifying novel therapeutic targets and suitable agents to target them with, and discovering molecular markers/signatures that predict response to therapy or optimal drug dose for each patient.