PTEN Loss Expands the Histopathologic Diversity and Lineage Plasticity of Lung Cancers Initiated by Rb1/Trp53 Deletion

Abstract

Introduction: High-grade neuroendocrine tumors of the lung such as SCLC are recalcitrant cancers for which more effective systemic therapies are needed. Despite their histopathologic and molecular heterogeneity, they are generally treated as a single disease entity with similar chemotherapy regimens. Whereas marked clinical responses can be observed, they are short-lived. Inter- and intratumoral heterogeneity is considered a confounding factor in these unsatisfactory clinical outcomes, yet the origin of this heterogeneity and its impact on therapeutic responses is not well understood.

Methods: New genetically engineered mouse models are used to test the effects of PTEN loss on the development of lung tumors initiated by Rb1 and Trp53 tumor suppressor gene deletion.

Results: Complete PTEN loss drives more rapid tumor development with a greater diversity of tumor histopathology ranging from adenocarcinoma to SCLC. PTEN loss also drives transcriptional heterogeneity as marked lineage plasticity is observed within histopathologic subtypes. Spatial profiling indicates transcriptional heterogeneity exists both within and among tumor foci with transcriptional patterns correlating with spatial position, implying that the growth environment influences gene expression.

Conclusions: These results identify PTEN loss as a clinically relevant genetic alteration driving the molecular and histopathologic heterogeneity of neuroendocrine lung tumors initiated by Rb1/Trp53 mutations.

Keywords: Genetically engineered mouse models; Small cell lung cancer; Tumor heterogeneity; Tumor suppressor genes.