ProLyPhy-GEP : Pesticide Associated Lymphomas: Expression of Treatment Resistance Genes

Occupational exposure to pesticides is associated with higher incidence of non-Hodgkin lymphoma (NHL), including diffuse large B-cell lymphoma (DLBCL) The relative risk for NHL after occupational exposure to pesticide is 1.5 to 3, with little variation according to NHL subtypes. DLBCL is one of the most frequent subtypes of NHL and characterized by aggressive presentation. DLBCL is treated by chemotherapy based on anthracyclines combined with an anti-CD20 monoclonal antibody allowing complete response and long term remission in 65-70% of patients. The response rate to treatment and clinical outcome is depending of the DLBCL subtype. There are 3 of them depending of the cell of origin (germinal centre B cell or activated B cell), and the anatomical location (primary mediastinal) identified by molecular gene expression profile. The activated B cell subtype have a worse outcome.

Lymphomagenesis is partially known, and some risk factor are identified like those inducing immune deficiencies: chronic exposure to HIV, immune suppressor therapies or commun variable immunodeficiency. Parts of the mechanisms leading to NHL development after pesticide exposure are the disruption of immune surveillance against cancer cell. Pro-oncogenic action of metabolites is the most important mechanisms of action for pesticides. Thus, pesticides are metabolized in pro-oxidant compounds disturbing the redox homeostasis in the haematopoietic and immune cells precursors, promoting proliferation and survival, and inducing DNA breaks. Some of them induce direct DNA breaks and non-conform reparation, leading to activation of oncogenes; and other induces transcription factors for oncogenic signalling pathways. DNA reparation and adaptation to a higher ROS level are associated with resistance against cytotoxic chemotherapy treatment with induction of detoxification mechanism by tumour cells.

That DNA repair pathways, which are targeted by chemotherapy could also explain a part of chemo-resistance. It was therefore suggested that DLBCL dependence to specific DNA repair pathways could be targeted to hamper repair of intrinsic DNA damage occurring during B-lymphoma cells proliferation or to increase DNA damage induced by chemotherapy.

The investigators hypothesize that actions of pesticides on DNA and redox homeostasis are critical events during lymphomagenesis. We supposed that specific mechanisms of DNA repair and antioxidant defences induced by pesticides exposure are implicated in the chemo-resistance in DLBCL patients.

There might be a negative impact of professional exposure to pesticide on treatment response.