Characterization of YAP as a rational companion target in lung cancer

PROJECT ABSTRACT. Lung cancer is the leading cause of cancer mortality worldwide, with non-small cell lung
cancer (NSCLC) the predominant histologic subtype of lung cancer and lung adenocarcinoma the major subset
of NSCLC. Despite clinical progress with the use of targeted therapies, drug resistance remains a problem that
limits patient survival. A less well understood aspect of the evolution of drug resistance is the drug tolerant,
“persister” cell state, in which a subpopulation of cancer cells survives initial targeted treatment to form a minimal
residual disease (MRD) reservoir that is a precursor to acquired resistance. We propose an innovative,
multidisciplinary and collaborative project to hopefully improve the survival of NSCLC patients by defining the
role that the Hippo-YAP pathway plays in promoting drug tolerance and MRD to current pathway targeted
therapies. Extending work that we completed in the first funding cycle of this R01, we aim to capitalize on our
discovery of the Hippo-YAP signaling pathway as a critical molecular circuit and therapeutic target in the many
cancers driven by hyperactivation of RTK-RAS-MAPK signaling. Our data suggest an emerging paradigm in
which YAP activation is a key functional feature of the drug tolerant state during RTK-RAS-MAPK targeted
inhibition in NSCLC. We observed YAP activation during therapy in multiple oncogene-driven NSCLC preclinical
models treated with EGFR, ALK, KRAS and SHP2 inhibitors. YAP upregulation promoted the expression of
several survival factors including BCL-xL and RTKs such as FGFR1 and ErbB2. Furthermore, through single-
cell RNA sequencing (scRNAseq) performed longitudinally in clinical specimens obtained from patients treated
with targeted inhibitors, we discovered that residual cancer cells often show lineage plasticity and a transition to
an alveolar type (AT)1/2-like transcriptional state that is a novel phenotype of slow cycling, drug tolerant cancer
cells. We verified this occurred in bona fide cancer cells (i.e., not from misannotated normal alveolar cells) and
was distinct from therapy-naïve adenocarcinoma or normal AT1/2 cells. Our data suggest a role for YAP in
promoting drug tolerance and this novel form of lineage plasticity. Inhibition of YAP signaling with YAP/TEAD
small molecule inhibitors that are in clinical development suppressed drug tolerant cancer cell survival and
expression of molecular markers of the AT1/2-like lineage switch. We propose to further test the hypothesis that
YAP signaling is a key molecular switch that regulates the biological and clinical response to RTK-MAPK pathway
inhibitors. In Aim 1, we define the role of YAP in promoting drug tolerance and the AT1/2-like lineage plasticity
present in drug tolerant cancer cells in RTK-RAS-MAPK-driven NSCLCs. We also test whether pharmacologic
inhibition of YAP/TEAD can thwart MRD and enhance response to RTK-RAS inhibitors in preclinical models. In
Aim 2, we study molecular features of YAP/TEAD activation and the AT1/2-like lineage switch as biomarkers of
MRD and clinical outcomes using tumors from patients before and on treatment. This project offers insight into
the role of YAP and lineage plasticity in therapy tolerance and MRD, with potential for future clinical translation.

Grant Number: 5R01CA204302-09
NIH Institute/Center: NIH
Principal Investigator: Trever Bivona