Cytotoxic drugs up-regulate epidermal growth factor receptor (EGFR) expression in colon cancer cells and enhance their susceptibility to EGFR-targeted antibody-dependent cell-mediated-cytotoxicity (ADCC).

Cetuximab is a human-murine chimeric IgG1 monoclonal antibody to epidermal growth factor-receptor (EGFR) which exerts synergistic antitumour interactions with several cytotoxic drugs. Therefore, it is presently recommended in combination with chemotherapy in the treatment of colon, head and neck and non-small cell lung cancer. Cetuximab has been designed to inhibit EGFR signalling; however, preclinical evidence suggests that its anti-cancer effects in vivo are also related to the ability of its human IgG1 backbone to trigger immunological mechanisms. Here we have investigated whether the exposure to different cytotoxic drugs may affect the susceptibility of colon cancer cells in vitro to cetuximab immuno-targeting and related lymphokine-activated killer (LAK)-mediated antibody-dependent cell cytotoxicity (ADCC). Five colon cancer cell lines expressing a different k-ras mutational status were evaluated for: (i) EGFR-expression, (ii) susceptibility to LAK cells and (iii) cetuximab-mediated ADCC, before and after exposure to 5-flurouracil (5-FU), gemcitabine (Gem), irinotecan (Iri) alone or in multiple two/three drug combinations. These drugs were able to up-regulate EGFR expression on the surface of all the colon cancer cell lines with a maximal effect observed few hours after the exposure to GILF regimen (Gem, Iri, Levofolinic acid and 5-FU). Chemotherapy was able to greatly enhance the sensitivity to either LAK cells or cetuximab-mediated ADCC in all the colon cancer cell lines with a mechanism independent from k-ras status. The results of our study suggest that chemotherapy may enhance cetuximab-mediated immuno-targeting and ADCC thus providing the rationale to design novel immuno-biochemotherapy regimens.

Regulatory (FoxP3+) T-cell tumor infiltration is a favorable prognostic factor in advanced colon cancer patients undergoing chemo or chemoimmunotherapy.

Antitumor immune response and chemotherapy-induced immunomodulation in colon cancer patients represented the rationale to design new strategies, like GOLFIG chemoimmunotherapy (gemcitabine, oxaliplatin, 5-fluorouracil/folinic acid, granulocyte macrophage colony-stimulating factor, and aldesleukine), that resulted a safe and very active regimen. Antitumor activity and immunity feedback to GOLFIG were strictly correlated with the best outcome observed in patients with autoimmunity signs, increase of central memory T cells, and decrease of regulatory T cells (Treg) in the peripheral blood. We thus investigated a potential correlation between the Treg tumor infiltration at diagnosis and the clinical outcome in a current randomized phase 3 trial aimed to compare the GOLFIG regimen with the standard FOLFOX chemotherapy (GOLFIG-2). An immunohistochemistry study was carried out to quantify the infiltration of Treg/FoxP3+ T lymphocytes in tumor samples of 57 patients enrolled in the GOLFIG-2 trial. Treg tumor infiltration scores were correlated with overall survival, treatment-relative survival, and progression-free survival (PFS). Higher Treg tumor infiltration scores were associated with a better prognosis in the whole series (Treg high score vs. low score: overall survival=mean 43.2 mo vs. 28.6 mo, P=0.0005) and a better outcome after treatment (Treg high score vs. low score: PFS=mean 15.8 mo vs. 8.8 mo, P=0.0009; treatment-relative survival=mean 23.1 mo vs. 18.2 mo, P=0.004). PFS was significantly longer in GOLFIG high versus all other subgroups (mean 18.1 mo vs. 9.9 mo, P=0.01). Our results suggest that a higher FoxP3+ T-lymphocyte tumor infiltration score is a favorable prognostic factor in colon cancer patients undergoing chemo or chemoimmunotherapy.