Etude de la réponse immunitaire dans les cancers colorectaux

• Auteur / Autrice : David Tougeron
• Direction : Thierry Frébourg
• Type : Thèse de doctorat
• Discipline(s) : Biologie
• Date : Soutenance en 2012
• Etablissement(s) : Rouen
• Ecole(s) doctorale(s) : École doctorale Normande de biologie intégrative, santé, environnement (Mont-Saint-Aignan, Seine-Maritime)
• Partenaire(s) de recherche : Laboratoire : INSERM U614 (Rouen)
• Jury : Examinateurs / Examinatrices : Jean-Claude Lecron, Thierry Lecomte, Julien Taieb, Jérôme Galon

Mots clés

Mots clés contrôlés

Immunothérapie anticancéreuse

Réponse immunitaire

Cancer colorectal

Résumé

It is now clearly established that the immune system plays an important role in tumor growth control, and a strong conflation between the presence of tumor infiltrating lymphocytes (TIL) in colorectal cancers (CRC) and patients' overall survival has been shown. The activation and expansion of tumor antigen-specific cytotoxic T lymphocytes (CTL) in vitro, followed by their administration to the patients, is a very promising approach for cancer treatment (adoptive immunotherapy). Artificial antigen-presenting cells (AAPC), allowing a powerful stimulation of CTL in all individuals sharing the same HLA class I molecule, were generated from murine fibroblasts. AAPC expressing carcinoembryonic antigen (CEA) failed to induce a specific CTL response against CEA (Article 1). The tolerance phenomena potentially involved in the lack of response observed against CEA led us to study neo-antigens, for which less tolerance phenomena are expected, in the context of CRC with RER+ (Replication errors) phenotype. The RER+ phenotype is found in 15% of CRC and is associated with an inactivation of DNA mismatch repair (MMR) system leading to genetic instability affecting repeated nucleotide sequences. This genetic instability causes mutations shifting the reading frame of genes carrying coding nucleotide repeat sequences. These shifts are responsible for the emergence of neo-antigens that may be immunogenic. Moreover, this phenotype is associated with a more important TIL density which is correlated with better patients' survival. In 61 RER+ CRC, we have demonstrated a correlation between infiltrating T cell (CD3+) density and mutation of two target genes: ASTEI and PTEN (Article 2). Currently, we are increasing the number of analyzed RER+ CRC (n=78) and we try to better characterize the tumor infiltrating cells (cytotoxic and regulatory T cells) using "Tissue microarray" (TMA). We have demonstrated a correlation beetween ASTEI, PTEN, and BAX mutations, and CTL (CD8+), but not regulatory T cell (FoxP3+) infiltrate. Neo-proteins corresponding to these mutations are therefore attractive targets to develop a cytotoxic T cell adoptive immunotherapy strategy in RER+ CRC. In parallel, we evaluated the immune response prognostic value in CRC RER+ and we demonstrated a correlation between the early metastatic invasion (venous emboli and lymphatic and perineural invasion) and regulatory T cell (FoxP3+) infiltration density (Article 3 in preparation). In addition, we implemented a clinical study on the prognostic value of lymphocyte infiltration in operated CRC in order to find a link with tumor recurrence at 2 years (TIL study). We have also begun an analysis of the cutaneous inflammatory response (acneiform papulo-pustular rash) associated with anti-EGFR (Epidermal growth factor receptor) treatment used in metastatic CRC (CUTACETUX study). This cutaneous toxicity is strongly correlated with treatment response. The study objective is to find a correlation between treatment response and skin inflammatory markers. Initial results show a Th17 cytokine expression increase in the skin. The ultimate aim of this work is a better understanding of the immune response mechanisms in CRC and the identification of tumor antigens for the development of adoptive immunotherapy strategy based on in vitro autologous CTL stimulation with our AAPC.