1. Proteomic analysis reveals Src/Stat and EGFR/MAPK pathways as potential mechanism of resistance to PI3K inhibitors in lung cancer
Maria Angelica Cortez1, Lauren Averett Byers1, You Hong Fan1, Lixia Diao2, Philip Groth3, Julianne Paul3, Jing Wang2, Uma Giri1, Jayanthi Gudikote1, Hai T. Tran1, Kevin Coombes2, John D. Minna4, Ningshu Liu3, John V. Heymach1.
1Department of Thoracic and Head and Neck Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston,Texas, 2Department of Bioinformatics and Computational Biology, University of Texas M.D. Anderson Cancer Center, Houston, Texas, 3Bayer Pharma AG, Berlin, Germany, 4Hamon Center for Therapeutic Oncology, University of Texas Southwestern Medical Center, Dallas, Texas
Background
The phosphoinositide 3-kinase (PI3K) signaling is the most commonly dysregulated pathway in many human cancers, including non-small cell lung cancer (NSCLC). Therefore, targeting PI3K signaling has become a promising approach in cancer therapy.
Although studies have indicated development of resistance to PI3K inhibitors, the molecular mechanism of drug resistance is largely unknown in NSCLC.
The goal of this study was to identify new potential mechanism of resistance to PI3K inhibitors.
Figure 1. Protein profiling by reverse phase protein array (RPPA) identifies pathways and proteins dysregulated in NSCLC cell lines treated with PI3K inhibitor BAY C.
Figure 5. Proposed mechanism of resistance to PI3K inhibitors. Suppression of mTOR pathway by PI3K inhibition upregulates Src/Stat pathway to promote cell survival.
PI3K/
mTOR
pathway
Src/Stat
EGFR/MAPK
Her2.pY1248
EGFR
Stat5.pY694
Src.pY416
Stat3.pY705
Met
Met.pY
Axl.pY702
mTOR.p2448
GSK3a.b.pS21.9
S6.pS
S6.pS
p70S6K.pT389
Akt.pT308
Akt.pS473
TSC2.pT1462
X4EBP1.pT70
X4EBP1.pS65
X4EBP1.pT37.46
Figure 3. Our analysis identified Src/Stat and EGFR/MAPK pathways as potential mechanism of resistance upon PI3K inhibition.
Methods
We used reverse-phase protein array (RPPA) to assess the expression levels and activation status of 137 proteins involved in signaling pathways implicated in lung cancer.
Seventy-four NSCLC cell lines were treated with the PI3K inhibitor BAY and lysates were collected for proteomic analysis.
Paired t-test was applied to each marker comparing the difference between drug and control treated cells.
We evaluated the association between drug sensitivity (IC50) and RPPA expression levels at baseline in sixty NSCLC cell lines. Correlation test was applied to each marker vs drug and Wilcox Rank test was performed to compare the smallest and largest one third of all the cell lines.
Conclusions
Our results suggest that PI3K inhibition leads to EGFR/MAPK and Src/Stat signaling activation in vitro, suggesting a compensatory pathway that may allow NSCLC survival.
Taken together, these results suggest that activation of Src/Stat pathway as an important mechanism of resistance to PI3K inhibitors in NSCLC and may be clinically relevant targets for combination therapy.
Figure 2. Treatment with BAY significantly downregulates downstream effectors (A and B) and upregulates negative regulators (C) of mTOR pathway. A.
Figure 4. Association between drug sensitivity (IC50) and RPPA expression levels at baseline.
Acknowledgements
This work was supported by UTSW and MDACC Lung SPORE 5 P50 CA070907; DoD PROSPECT W81XWH ; CCSG grant 5 P30 CA016672; Chapman Fund for Bioinformatics in Personalized Cancer Therapy, 1 U24 CA143883; Bayer Pharmaceuticals. B.
A549
H441
H460
Calu1 + - + - + - + - SF FS
PI3Ki (1μM)
S6.pS
TSC2.pT1462
p70S6K.pT389
Vinculin