Mismatch repair gene defects in sporadic colorectal cancer enhance immune surveillance
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Marco Scarpa1,*, Cesare Ruffolo2,*, Fabio Canal3, Melania Scarpa1, Silvia Basato4, Francesca Erroi4, Alain Fiorot2, Lucia Dall’Agnese4, Anna Pozza4, Andrea Porzionato5, Ignazio Castagliuolo5, Angelo P. Dei Tos3, Nicolò Bassi2 and Carlo Castoro1
1 Surgical Oncology Unit, Veneto Institute of Oncology IOV-IRCCS, Padova, Italy
2 General Surgery Unit (IV), “Ca’ Foncello” Hospital, Treviso, Italy
3 Pathology Unit, “Ca’ Foncello” Hospital, Treviso, Italy
4 Department of Surgical, Oncological and Gastroenterological Sciences, University of Padova, Padova, Italy
5 Department of Molecular Medicine, University of Padova, Padova, Italy
* These authors have contributed equally to this work
Marco Scarpa, email:
Keywords: mismatch repair, colorectal cancer, immune surveillance, CD80
Received: June 03, 2015 Accepted: October 07, 2015 Published: October 19, 2015
Background: There is evidence that colorectal cancers (CRC) with DNA mismatch repair deficiency (MMR-D) are associated with a better prognosis than the generality of large bowel malignancies. Since an active immune surveillance process has been demonstrated to influence CRC outcome, we investigated whether MMR-D can enhance the immune response in CRC.
Patients and Methods: A group of 113 consecutive patients operated for CRC (42 stage I or II and 71 with stage III or IV) was retrospectively analyzed. The expression of MMR genes (MSH2, MLH1, MSH6 and PSM2) and co-stimulatory molecule CD80 was assessed by tissue microarray immunohistochemistry. In addition, tumor infiltrating mononuclear cells (TIMC) and T cell subpopulations (CD4, CD8, T-bet and FoxP-3) were quantified. The effect of specific siRNA (siMSH2, siMLH1, siMSH6 and siPSM2) transfection in HT29 on CD80 expression was quantified by flow cytometry. Non parametric statistics and survival analysis were used.
Results: Patients with MMR-D showed a higher T-bet/CD4 ratio (p = 0.02), a higher rate of CD80 expression and CD8 lymphocyte infiltration compared to those with no MMR-D. Moreover, in the MMR-D group, the Treg marker FoxP-3 was not expressed (p = 0.05). MMR-D patients with stage I or II and T-bet expression had a significant better survival (p = 0.009). Silencing of MSH2, MLH1 and MSH6, but not PSM2, significantly increased the rate of CD80+ HT29 cells (p = 0.007, p = 0.023 and p = 0.015, respectively).
Conclusions: CRC with MMR-D showed a higher CD80 expression, and CD8+ and Th1 T-cell infiltration. In vitro silencing of MSH2, MLH1 and MSH6 significantly increased CD80+ cell rate. These results suggest an enhanced immune surveillance mechanism in presence of MMR-D.
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