Non-epithelial Circulating Tumor Cells Enhance Disease Progression in High-risk Prostate Cancer through EMT and COL1A1 Expression

<b>Introduction:</b> Circulating tumor cells (CTCs) are important prognostic indicators for malignancies. However, a reliable positive/negative cutoff value of non-epithelial (NE⁺: hybrid and mesenchymal) CTCs phenotype in prostate cancer (PCa) patients has not been established. Here, we aimed to determine the cutoff value and the prognostic value of NE⁺ CTCs in high-risk prostate cancer (HRPC) patients after radical prostatectomy (RP). <b>Methods:</b> The cutoff value of NE⁺ CTCs was established in spiking experiments, and CTCs were detected in 208 HRPC patients using the CanPatrol^TM platform. The expression and function of COL1A1 in PCa were examined via qRT-PCR, Western blot, wound healing assay, Transwell assay, and immunohistochemistry (IHC). <b>Results:</b> The cutoff value of NE⁺ CTCs was determined to be 45% by spiking experiments. In 208 HRPC patients, the NE⁺ CTCs positive group had higher prostate-specific antigen (PSA) levels, more advanced pathological tumor stage, and lymph node stage (<i>P</i> < 0.001, <i>P</i> = 0.002 and 0.002, respectively). Besides, patients with NE⁺ CTCs ≥ 45% had a shorter median progression-free survival (PFS) than those with NE⁺ CTCs < 45% (44.5 vs. 51.0 months, hazard ratio = 3.31, <i>P</i> < 0.05). Moreover, we identified that COL1A1 was associated with a high proportion of NE⁺ CTCs in HRPC patients via an EMT mechanism. <b>Conclusion:</b> Our findings suggest that NE⁺ CTCs represent a reliable prognostic indicator for HRPC patients and that targeting COL1A1 may prevent the formation of NE⁺ CTCs.