DCLK1-mediated regulation of invadopodia dynamics and matrix metalloproteinase trafficking drives invasive progression in head and neck squamous cell carcinoma.

Background: HNSCC presents a significant health challenge due to its high mortality resulting from treatment resistance and locoregional invasion into critical structures in the head and neck region. Understanding the invasion mechanisms of HNSCC has the potential to guide targeted therapies, improving patient survival. Previously, we demonstrated the involvement of doublecortin like kinase 1 (DCLK1) in regulating HNSCC cell invasion. Here, we investigated the hypothesis that DCLK1 modulates proteins within invadopodia, specialized subcellular protrusions that secrete matrix metalloproteinases to degrade the ECM.

Methods: We employed tandem mass tag (TMT)-based proteomics to identify the role of DCLK1 in regulating proteins involved in HNSCC invasion and validated the findings using immunoblotting. The Cancer Genome Atlas (TCGA) database was interrogated to correlate DCLK1 expression with tumor stage, grade, and invasion-associated proteins. In vitro invasion was assessed using a Boyden chamber assay, and immunohistochemistry on patient samples determined DCLK1's distribution within tumors. Gelatin invadopodia assay was used to establish DCLK1 localization to invadopodia related gelatin degradation. Super-resolution confocal microscopy demonstrated colocalization of DCLK1 with invadopodia markers and MMP trafficking proteins. ECM degradation by MMPs in HNSCC cells with wild-type and knockdown DCLK1 was evaluated using a dye-quenched tracer, while gel zymography and MMP array identified secreted proteases. Proximity ligation assay (PLA) and co-immunoprecipitation assays were used to confirm interactions between DCLK1, MMP9, KIF16B, and RAB40B.

Results: Proteomic analysis demonstrate DCLK1's role in regulating proteins involved in cytoskeletal and ECM remodeling. Clinically, rising DCLK1 levels correlate with higher histological grade and lymph node metastasis, with heightened expression observed at the leading edge of HNSCC patient tissue. DCLK1 is localized with markers of mature invadopodia including TKS4, TKS5, cortactin, and MT1-MMP. Knockdown of DCLK1 led to reductions in invadopodia numbers and decreased in vitro invasion and ECM degradation. MMP9 colocalizes with DCLK1 within invadopodia structures and its secretion is disrupted by DCLK1 knockdown. Further, PLA and co-immunoprecipitations studies demonstrate DLCK1 complexes with KIF16B and RAB40B enabling trafficking of degradative MMP9 cargo along the invadopodia to degrade local ECM.

Conclusion: This work unveils a novel function of DCLK1 in regulating KIF16B and RAB40B to traffic matrix degrading MMP9 cargo to the distal end of the invadopodia facilitating HNSCC invasion.