Modulation of mutant KrasG12D-driven lung tumorigenesis in vivo by gain or loss of PCDH7 function

PROTOCADHERIN 7 (PCDH7), a transmembrane receptor and member of the Cadherin superfamily, is frequently overexpressed in lung adenocarcinoma and is associated with poor clinical outcome. While PCDH7 was recently shown to promote transformation and facilitate brain metastasis in lung and breast cancers, decreased PCDH7 expression has also been documented in colorectal, gastric, and invasive bladder cancers. These data suggest context-dependent functions for PCDH7 in distinct tumor types. Given that PCDH7 is a potentially targetable molecule on the surface of cancer cells, further investigation of its role in tumorigenesis in vivo is needed to evaluate the therapeutic potential of its inhibition. Here we report the analysis of novel PCDH7 gain- and loss-of-function mouse models and provide compelling evidence that this cell-surface protein acts as a potent lung cancer driver. Employing a Cre-inducible transgenic allele, we demonstrated that enforced PCDH7 expression significantly accelerates KrasG12D-driven lung tumorigenesis and potentiates MAPK pathway activation. Furthermore, we performed in vivo somatic genome editing with CRISPR/Cas9 in KrasLSL-G12D; Tp53fl/fl (KP) mice to assess the consequences of PCDH7 loss of function. Inactivation of PCDH7 in KP mice significantly reduced lung tumor development, prolonged survival, and diminished phospho-activation of ERK1/2. Together, these findings establish a critical oncogenic function for PCDH7 in vivo and highlight the therapeutic potential of PCDH7 inhibition for lung cancer. Moreover, given recent reports of elevated or reduced PCDH7 in distinct tumor types, the new inducible transgenic model described here provides a robust experimental system for broadly elucidating the effects of PCDH7 overexpression in vivo.\n\nAUTHOR SUMMARYLung cancer is the leading cause of cancer-associated deaths worldwide. PROTOCADHERIN 7 (PCDH7), cell surface protein and member of the Cadherin superfamily, is frequently overexpressed in lung adenocarcinomas and is associated with poor clinical outcome. Nevertheless, it has yet to be shown in vivo whether PCDH7 plays a role in the initiation and progression of lung cancer, and whether it represents an actionable therapeutic target. Here we demonstrate, using a novel transgenic mouse model, that PCDH7 overexpression accelerates KrasG12D-driven lung tumorigenesis. Furthermore, we validate PCDH7 as a therapeutic target by knocking it out using in vivo somatic genome editing in the KrasLSL-G12D; Tp53fl/fl (KP) model. Our results provide new insight into the mechanisms that drive lung cancer pathogenesis and, because targeting oncogenic cell-surface proteins with antibodies has proven to be a highly effective anti-cancer therapeutic strategy, establish a new target for cancer treatment. Moreover, given recent reports of elevated or reduced PCDH7 in distinct tumor types, the transgenic PCDH7 model described here provides a robust experimental system for elucidating the effects of PCDH7 overexpression in different in vivo settings. This model will also provide an ideal system for future testing of therapeutics directed at PCDH7.