Graduate Biochemistry Group
M.S. Defense
Wednesday, May 18, 2016
Johnson Cancer Center Conference Room
36 Chalmers Hall, 1:00 p.m.
Refreshments will be served at 12:45 p.m.
Jacob Hodge
B.S./M.S. Student
Dr. Anna Zolkiewska’s Lab
Regulation of the MEK/ERK signaling cascade by ADAM12
in Triple-Negative Breast Cancer cells
Mitogen-activated protein kinase (MAPK) signaling plays an important role in proliferation,
survival, and therapy resistance of breast cancer cells. Two important protein kinases
involved in the MAPK pathway are MEK and ERK. The MEK/ERK signaling cascade can be
stimulated by activation of epidermal growth factor receptor (EGFR) upon binding of EGFlike ligands, which are released from cells by ADAM proteases. In a particularly aggressive
form of breast cancer, triple-negative breast cancer (TNBC), EGFR is frequently overexpressed.
Our analysis of clinical data revealed that high expression of ADAM12, but not other ADAMs,
in TNBC is associated with poor patient survival. Thus, we hypothesized that ADAM12 plays
a critical role in the progression of TNBC, possibly by stimulating MEK/ERK activity in an
EGFR-dependent manner. To test this hypothesis, ADAM12 was knocked-down (KD) in
SUM159PT TNBC cells, which express high levels of the endogenous ADAM12 protein. The
extent of phosphorylation of tyrosine residues in EGFR, before and after ADAM12 KD, was
tested to determine the level of EGFR activation. An antibody array assay indicated a
significant decrease in the activation of the MAPK pathway in SUM159PT cells after
ADAM12 KD. The decrease in MAPK activity was further confirmed by Western blotting
using phospho-MEK and phospho-ERK specific antibodies. Additionally, conditioned media
from ADAM12-deficient SUM159PT cells failed to support the survival of MCF10A cells,
suggesting that ADAM12 KD reduced the release of pro-survival growth factors from
SUM159PT cells. We propose that ADAM12 is a novel regulator of the MAPK pathway and a
potential therapeutic target in breast cancer.