ABL kinase inhibition sensitizes SCLC to dysregulation of metabolic pathways leading to cell death

ABSTRACT
Prognosis for patients with small cell lung cancer (SCLC) remains poor due to high rates of metastatic disease,
vast intra-tumoral heterogeneity, limited therapeutic options, and rapid development of therapeutic resistance.
Our lab has recently shown that Abelson (ABL) family kinase inhibitors are effective in the treatment of SCLC
metastases in vivo. Targeted combination therapies can minimize cytotoxic adverse events and impair the
development of resistance. Thus, we performed a whole-genome CRISPR/Cas9 loss-of-function sensitization
screen to identify synergizing combination therapy targets with the ABL allosteric inhibitor ABL001. Consistent
with prior observations that ABL kinase inhibition dysregulates mitochondrial and metabolic function in lung
adenocarcinoma, numerous top sensitizers to ABL kinase inhibition revealed by the screen are involved in the
processing and clearance of metabolic products. Preliminary validation of the screen has shown that inhibition
of organic anion MCT transporters synergizes with ABL001 to cause cell death as a consequence of a
mitochondrial dysregulation phenotype observed in lung cancer cells following treatment with allosteric ABL
kinase inhibitors. Furthermore, targeted metabolomic sequencing revealed that following combination treatment
with ABL and MCT inhibitors, the levels of numerous metabolite species become significantly dysregulated.
These changes are consistent with the stalling of glutaminolysis and are most strikingly characterized by a
significant decrease in glutathione, an important mediator of metabolic stress responses. My hypothesis is that
the metabolic stress induced by inhibition of the ABL kinases when paired with MCT inhibition, results in the
stalling of glutaminolysis and the subsequent loss of glutathione, thereby promoting ferroptosis, and contributing
to the synergistic cell death phenotype observed. The aims of this proposal are 1) to determine how the ABL
kinases mediate homeostatic metabolic function and define the mechanism of metabolic dysregulation following
ABL kinase inhibition, 2) to determine the mechanism of dysregulation of glutaminolysis following combined ABL
kinase and MCT inhibition, and 3) assess the extent to which this combined therapy contributes to cell death via
ferroptosis. Approaches to address these objectives include metabolic profiling via stable isotope tracing of
glucose and glutamine, and Seahorse assays to measure oxidative and glycolytic energy metabolism. We will
also assess the extent to which this combination treatment induces ferroptotic cell death by in vitro drug-
treatment and isogenic knockout experiments. Subsequently we will perform in vivo drug treatment experiments
to assess the efficacy of combined ABL and MCT inhibition in the treatment of SCLC in mouse models. This
investigation into the role of the ABL kinases in metabolic dynamics will explore a novel mechanism of regulation
of mitochondrial homeostasis by the ABL kinases, as well as evaluate a potential treatment modality for patients
with SCLC.

Grant Number: 5F31CA290817-02
NIH Institute/Center: NIH
Principal Investigator: Roberto Barbier