Dual targeting of PDPK1 and BRAF V600E is synthetically lethal

PDPK1 functions downstream of PI3K and is essential for activating AKT and other AGC kinases. Although PDPK1 has a central role in the PI3K/AKT/mTOR signaling pathway, there has been limited evaluation of it as a target for cancer therapy. Anaplastic thyroid cancer (ATC) has one of the highest mortality rates of all human malignancies. Although combined BRAF and MEK inhibition in BRAF V600E mutant ATC (present in 45% of cases) results in response, resistance is common, and there is no curative treatment for ATC. The majority (up to 95.8%) of ATC cases have activation in the PI3K/AKT/mTOR and RAS/RAF/MEK/MAPK pathways due to genetic alterations involved in these pathways. In this study, we investigated PDPK1 as a therapeutic target for ATC. We used in vitro, ex vivo, and in vivo ATC models to evaluate the effect of targeting PDPK1 (BX795) alone and in combination with BRAF V600E inhibition (dabrafenib), and the mechanism of action that resulted in ATC cell death. BX795 monotherapy significantly reduced ATC cell proliferation, invasion, colony formation, and spheroid size. Combination BX795 and dabrafenib treatment had strong synergistic anticancer activity in BRAF V600E-mutant ATC models and led to simultaneous and sustained suppression of PDPK1/AKT and MAPK signaling, preventing the compensatory pathway reactivation observed with single-agent treatment. Mechanistically, combined inhibition induced pronounced oxidative stress, DNA damage, and G2-phase cell-cycle arrest, accompanied by mitochondrial dysfunction and robust activation of apoptosis in ATC cells. These effects resulted in marked tumor regression in in vitro, ex vivo, and in vivo ATC models. Our findings identify PDPK1 as a critical therapeutic vulnerability in ATC. Co-targeting PDPK1 and BRAF V600E produces potent synergistic anticancer activity by shutting down convergent oncogenic signaling pathways and amplifying apoptotic stress responses. These data support PDPK1 inhibition alone and in combination with BRAF blockade as a promising therapeutic strategy in BRAF V600E-mutant cancers.