Residual tumor micro-foci and overwhelming regulatory T lymphocyte infiltration are the causes of bladder cancer recurrence

// Alessia Parodi 1,* , Paolo Traverso 1,2,3,* , Francesca Kalli 1 , Giuseppina Conteduca 1 , Samuele Tardito 1 , Monica Curto 1 , Federica Grillo 2,3 , Luca Mastracci 2,3 , Cinzia Bernardi 1 , Giorgia Nasi 1 , Francesco Minaglia 2,3 , Alchiede Simonato 2,3 , Giorgio Carmignani 2,3 , Francesca Ferrera 1 , Daniela Fenoglio 1,3,4 and Gilberto Filaci 1,3,4 1 Centre of Excellence for Biomedical Research, University of Genoa, Genoa, Italy 2 Department of Surgical Sciences and Integrated Diagnostics, University of Genoa, Genoa, Italy 3 IRCCS Azienda Ospedaliero Universitaria San Martino – IST - Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy 4 Department of Internal Medicine, University of Genoa, Genoa, Italy * These authors have contributed equally to this work Correspondence to: Gilberto Filaci, email: // Keywords : bladder cancer, tumor infiltrating lymphocytes, MAGE, Th1, Th17, Immunology and Microbiology Section, Immune response, Immunity Received : September 21, 2015 Accepted : January 02, 2016 Published : January 25, 2016 Abstract Bladder cancer has an unexplained, high recurrence rate. Causes of recurrence might include the presence of sporadic tumor micro-foci in the residual urothelial tissue after surgery associated with an inverted ratio between intratumoral effector and regulatory T cell subsets. Hence, surgical specimens of both tumors and autologous, macroscopically/histologically free-of-tumor tissues were collected from 28 and 20 patients affected by bladder or renal cancer, respectively. The frequencies of effector (IFNγ+ and IL17+ T cells) and regulatory (CD4+CD25hiCD127lo and CD8+CD28-CD127loCD39+ Treg) T cell subpopulations among tumor infiltrating lymphocytes were analyzed by immunofluorescence, while the gene expression of MAGE-A1 and MAGE-A2 tumor-associated antigens was studied by RT-PCR. The results show that both the T cell infiltrate and the frequency of MAGE-A1/A2 gene expression were comparable in tumors and in autologous free-of-tumor tissues in bladder cancer, while the autologous free-of-tumor renal tissues showed reduced T cell infiltrate and frequency of MAGE gene expression as compared to the autologous tumors. Importantly, the intra-tumor T effector/Treg cell ratio was consistently 1 in patients (n. 6) without recurrence (regardless of tumor stage) ( P = 0.0006, Odds ratio = 195). These unprecedented findings clarify the pathogenic mechanism of bladder cancer recurrence and suggest that microscopically undetectable micro-foci of tumor may predispose to recurrence when associated with an inverted intratumoral T effector/Treg cell ratio.