Novel Combination Therapy Targeting Oncogenic Signaling Kinase P21-Activated Kinase 1 and Chemotherapeutic Drugs Against Triple-Negative Breast Cancer.

Most of the triple-negative phenotypes or basal-like molecular subtypes of breast cancers are associated with aggressive clinical behavior and show poor disease prognosis. Current treatment options are constrained, emphasizing the need for novel combinatorial therapies for this particular tumor subtype. Our group has demonstrated that functionally active p21-activated kinase 1 (PAK1) exhibits significantly higher expression levels in clinical triple-negative breast cancer (TNBC) samples compared with other subtypes, as well as adjacent normal tissues. Low PAK1 expression in TNBC was significantly linked to better prognosis, with improved overall survival (P = 0.00236) and relapse-free survival (P = 0.0314), as shown by Gene expression-based Outcome for Breast cancer Online analysis. To confirm the role of PAK1 as a therapeutic target and to discover novel synergistic chemotherapy drug combinations, we conducted a drug combination screen using TNBC cell lines and a mouse metastatic tumor cell line. We identified the combined inhibition of PAK1 inhibitor NVS-PAK1 with doxorubicin/paclitaxel/methotrexate as a synergistic novel therapeutic approach for treating metastatic TNBC to improve overall survival. This study also indicated a reduction in the effective dosage of the chemotherapeutic drug when combined with NVS-PAK1. Our study demonstrates that combining NVS-PAK1 with each individual chemotherapeutic drug such as doxorubicin, paclitaxel, and methotrexate resulted in decreased colony formation, reduced wound-healing capability, and diminished migratory and invasive potential in both TNBC cell lines and 4T1 in vitro. These findings were further validated in orthotopic mouse mammary tumors, confirming that simultaneous PAK1 inhibition alongside chemotherapy significantly enhanced antitumor efficacy and reduced metastasis.