Phosphoproteomics Provides Novel Insights into the Response of Primary Acute Lymphoblastic Leukemia Cells to Microtubule Depolymerization in G1 Phase of the Cell Cycle

Microtubule targeting
agents (MTAs) have been used for the treatment
of cancer for many decades and are among the most successful chemotherapeutic
agents. However, their application and effectiveness are limited because
of toxicity and resistance as well as a lack of knowledge of molecular
mechanisms downstream of microtubule inhibition. Insights into key
pathways that link microtubule disruption to cell death is critical
for optimal use of these drugs, for defining biomarkers useful in
patient stratification, and for informed design of drug combinations.
Although MTAs characteristically induce death in mitosis, microtubule
destabilizing agents such as vincristine also induce death directly
in G1 phase in primary acute lymphoblastic leukemia (ALL) cells. Because
many signaling pathways regulating cell survival and death involve
changes in protein expression and phosphorylation, we undertook a
comprehensive quantitative proteomic study of G1 phase ALL cells treated
with vincristine. The results revealed distinct alterations associated
with c-Jun N-terminal kinase signaling, anti-proliferative signaling,
the DNA damage response, and cytoskeletal remodeling. Signals specifically
associated with cell death were identified by pre-treatment with the
CDK4/6 inhibitor palbociclib, which caused G1 arrest and precluded
death induction. These results provide insights into signaling mechanisms
regulating cellular responses to microtubule inhibition and provide
a foundation for a better understanding of the clinical mechanisms
of MTAs and for the design of novel drug combinations. The mass spectrometry
proteomics data have been deposited to the PRIDE Archive (http://www.ebi.ac.uk/pride/archive/) via the PRIDE partner repository with the data set identifier PXD027190
and 10.6019/PXD027190.