272 Neurotrophin receptors: conflicting roles in cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent form of skin cancer showing a rapidly increasing incidence worldwide. NTs mediate their effects through the common neurotrophin receptor CD271 and the tyrosine kinases family of receptors (Trks). In the skin, CD271 is implicated in the switch between stem and early progenitors, while Trk receptors mediate cell survival. However, the precise role of NTreceptors in cSCC is still to be defined. Gene and protein expression analysis revealed that CD271 overexpression, while reducing SCC spheroid growth and increasing apoptosis, down-regulates TrkA and Survivin, both required for keratinocyte stemness. Conversely, CD271 silencing upregulates TrkA, as well as CXCL8, which is associated with cancer invasion. Moreover, CD271 silencing increases viability and aggressiveness of cSCC, as further demonstrated by the cSCC zebrafish model By using the novel flow-based W8TM machine, we show that CD271 overexpression significantly increases mass density, reduces their weight and diameter. RNAseq analysis of CD271 overexpressing spheroids show a major fold-enrichment in cell differentiation and keratinization genes. CD271 overexpressing spheroids display low TrkA and Ki67 expression, while the expression of Keratin 1 is increased. TrkA/Fc chimera decreases cell viability and SCC spheroid invasion area, confirming the dependence of SCC cells from the autocrine NTs. K252, that blocks Trk phosphorylation, reduces spheroid invasion to the same extent as chemotherapy or 5FU, the effect being upregulated by CD271 overexpression. K252 or CD271 overexpression improves the outcome of photodynamic therapy or chemotherapy, as measured by cSCC spheroid size and viability. Our data strongly indicate the opposite functions of NT receptors in cSCC, and their modulation may be a potential treatment strategy in this cancer.