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Targeting SHP2 Sensitizes Papillary Thyroid Cancer Cells to MEK Inhibitors

Background: Pharmacologic targeting of components of the MAPK/ERK pathway in differentiated thyroid carcinoma (DTC) is often limited due to the development of adaptive resistance. However, the detailed mechanism of MEK inhibitor (MEKi) resistance is not fully understood. 
 
Methods: RNA-seq of the constructed MEKi-resistant DTC cell line BCPAP-R (compared with the BCPAP line) was performed to investigate the intrinsic mechanism of drug resistance. Colony formation assays, cell viability assays, and cell cycle analysis were performed, and various murine models, including xenograft models, long-term MEKi-treated models, and transgenic model were used to evaluate the treatment effect of combination therapy (SHP099 and selumetinib).  
 
Findings: MEKi-resistant models were constructed successfully, in which multiple receptor tyrosine kinases (RTKs) signaling pathways and Src-homology 2 domain-containing phosphatase 2 (SHP2) were activated in MEKi-resistant cells. Given the physiological role of SHP2 as the downstream target of many RTKs, we first found that blockade of SHP2 enhanced the sensitivity to MEKi in constructed MEKi-resistant thyroid cancer models (including constructed cell lines and a long-term MEKi-treated murine model). Interestingly, we also found that compared with MEKi treatment alone, MEKi in combination with an SHP2 inhibitor markedly suppressed the reactivation of the MEK/ERK pathway; thus, the addition of the SHP2 inhibitor significantly improved the anti-tumor effects of MEKi. The synergistic suppression of DTC upon treatment with both inhibitors was futher confirmed in xenograft models and transgenic models. 
 
Interpretation: RTKs activation leads to reactivation of the MAPK pathway and resistance to MEKi in DTC, which is reversed by SHP2 blockade. As a novel active inhibitor of SHP2, SHP099 in combination with selumetinib is a promising therapeutic approach for advanced DTC and MEKi-resistant one.  
 
Funding Statement: This work was partially supported by grants from the National Natural Science Foundation of China (GRANT no. 81872169), Tianjin Key Research and Development Program Science and Technology Support Key Projects (grant no. 17YFZCSY00690), and Tianjin Municipal Science and Technology Project (grant no. 19JCYBJC27400). 
 
Declaration of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 
 
Ethics Approval Statement: All animal experiments were approved by the Tianjin Medical University Cancer Institute and the Hospital Animal Care and Use Committee and performed according to the IACUC protocol.