Prevention of in Situ Recurrence and Distant Metastasis in Feline Mammary Carcinoma Treated with Plasmonic Photothermal Therapy

Abstract Most of the felines with mammary carcinoma (MC) exhibit an aggressive metastatic phenotype. A slew of studies has implicated breast cancer stem cells (BCSCs) with the phenotypes CD44 + /CD24 - and/or CD133 + in the promotion of invasive and metastatic MC. Where BCSCs are resistant to conventional chemo- and radiotherapies, gold nanorods (AuNRs)-mediated plasmonic photothermal therapy (PPTT) selectively eradicates BCSCs. In this study, we investigated for the first time the anti-tumor activity of AuNRs PPTT by flow cytometry analysis (FCA) of the circulatory BCSCs in the PB of cats with spontaneous metastatic and non-metastatic forms of MC. The PPTT was applied either alone (GA = 7) or in combination with mastectomy (GB = 3). In one test, BCSCs were identified as CD133 + , while in another, they were identified as a CD44 + /CD24 - combination. With a survival rate of 50%, the non-metastatic cats in GA revealed complete tumor ablation 6–8 weeks post-treatment and complete wound healing in GB, no in situ recurrence or distant metastasis over the observation period with a statistically significant drop in cBCSC counts ( P = 0.00512). Lung metastasis persisted in metastatic cats in both groups with a statistically significant rise in cBCSC counts ( P = 0.008). The prognostic significance cutoff values were >996 for (CD44 + /CD24 - ) phenotypes and >110 for CD133 + cells. That implies that BCSCs are highly susceptible to PPTT in non-metastatic queens, unlike metastatic cats, and indicates the FCA of cBCSCs as an accurate and non-invasive method for therapy monitoring in FMC.