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Breast cancer; Drug tolerance; Secretome Cáncer de mama; Tolerancia a los fármacos; Secretoma Càncer de mama; Tolerància als fàrmacs; Secretoma Drug tolerant persister (DTP) cells enter into a reversible slow-cycling state after drug treatment. We performed proteomic characterization of the breast cancer (BC) DTP cell secretome after eribulin treatment. We showed that the growth differentiation factor 15 (GDF15) is a protein significantly over-secreted upon eribulin treatment. The biomarker potential of GDF15 was confirmed in 3D-cell culture models using BC cells lines and PDXs, as well as in a TNBC in vivo model. We also found that GDF15 is required for survival of DTP cells. Direct participation of GDF15 and its receptor GFRAL in eribulin-induction of DTPs was established by the enhanced cell killing of DTPs by eribulin seen under GDF15 and GFRAL loss of function assays. Finally, we showed that combination therapy of eribulin plus an anti-GDF15 antibody kills BC-DTP cells. Our results suggest that targeting GDF15 may help eradicate DTP cells and block the onset of acquired resistance. This research was funded by Eisai Inc.

Simple Summary Drug resistance is the principal limiting factor to achieving good survival rates in patients with cancer. The identification of potential biomarkers for diagnosis and prognostic prediction, as well as the design of new molecular-targeted treatments, will be essential to improving head and neck squamous cell carcinoma (HNSCC) patient outcomes. In this sense, the sensitization of resistant cells and cancer stem cells (CSCs) represents a major challenge in cancer therapy. We conducted a proteomic study involving cisplatin-resistance and CSCs with the aim to unravel the molecular and cellular mechanisms by which tumor cells acquire resistance to chemotherapy. Syntenin-1 (SDCBP) was identified as an important protein involved in the chemoresistance and stemness of HNSCC tumors. Abstract To characterize the mechanisms that govern chemoresistance, we performed a comparative proteomic study analyzing head and neck squamous cell carcinoma (HNSCC) cells: CCL-138 (parental), CCL-138-R (cisplatin-resistant), and cancer stem cells (CSCs). Syntenin-1 (SDCBP) was upregulated in CCL-138-R cells and CSCs over parental cells. SDCBP depletion sensitized biopsy-derived and established HNSCC cell lines to cisplatin (CDDP) and reduced CSC markers, Src activation being the main SDCBP downstream target. In mice, SDCBP-depleted cells formed tumors with decreased mitosis, Ki-67 positivity, and metastasis over controls. Moreover, the fusocellular pattern of CCL-138-R cell-derived tumors reverted to a more epithelial morphology upon SDCBP silencing. Importantly, SDCBP expression was associated with Src activation, poor differentiated tumor grade, advanced tumor stage, and shorter survival rates in a series of 382 HNSCC patients. Our results reveal that SDCBP might be a promising therapeutic target for effectively eliminating CSCs and CDDP resistance.

Sensitization of resistant cells and cancer stem cells (CSCs) represents a major challenge in cancer therapy. A proteomic study revealed tetraspanin-1 (TSPAN1) as a protein involved in acquisition of cisplatin (CDDP) resistance (Data are available via ProteomeXchange with identifier PXD020159). TSPAN1 was found to increase in CDDP-resistant cells, CSCs and biopsies from head and neck squamous cell carcinoma (HNSCC) patients. TSPAN1 depletion in parental and CDDP-resistant HNSCC cells reduced cell proliferation, induced apoptosis, decreased autophagy, sensitized to chemotherapeutic agents and inhibited several signaling cascades, with phospho-SRC inhibition being a major common target. Moreover, TSPAN1 depletion in vivo decreased the size and proliferation of parental and CDDP-resistant tumors and reduced metastatic spreading. Notably, CDDP-resistant tumors showed epithelial&ndash, mesenchymal transition (EMT) features that disappeared upon TSPAN1 inhibition, suggesting a link of TSPAN1 with EMT and metastasis. Immunohistochemical analysis of HNSCC specimens further revealed that TSPAN1 expression was correlated with phospho-SRC (pSRC), and inversely with E-cadherin, thus reinforcing TSPAN1 association with EMT. Overall, TSPAN1 emerges as a novel oncogenic protein and a promising target for HNSCC therapy.