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PD-L1 protein expression in tumour cells and immune cells in mismatch repair protein-deficient and -proficient colorectal cancer: the foundation study using the SP142 antibody and whole section immunohistochemistry
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  • Published on:
    Loss of MMR proteins expression as predictive marker for immunotherapy in malignant melanoma patients
    • Giovanni Ponti, Assistant Professor in Clinical Pathology University of Modena and Reggio Emilia
    • Other Contributors:
      • Giovanni Pellacani, Full Professor
      • Marco Manfredini, resercher

    El Jabbour T et al. (Jun 2017) described the association between immunohistochemical PD-L1 positivity and loss of MMR proteins in colorectal cancer. However, the evaluation of Mismatch Repair Deficiency (dMMR) as a immunotherapy predictive marker is lacking for Malignant Melanoma (MM) and other malignancies, such as genitourinary, prostate, bladder, head and neck cancers, that are treated with immune checkpoint inhibitors (ICPI).

    We recently assessed dMMR in MM patients treated with anti-PD-1/PD-L1 during 2014-2016 at University of Modena and Reggio Emilia: 7% of primary melanoma and 13% of metastasis showed the dMMR. We report a patient whose primary MM and metastasis showed dMMR with immunohistochemical lack of MSH6 expression. Her complex history was characterized by the regression of the multiple cerebral and visceral metastases after anti-PD-L1 therapy, and an extraordinary progression-free survival (1150 days) and overall-survival (2646 days). At present, she is still alive and well, and had the longest response to anti-PD-L1 treatment.

    Our results emphasize that the immunohistochemical assessment of MMR protein expression in MM patients represents a useful predictive marker, which may have crucial importance for the determination of the response of anti-PD-1/PD-L1 therapy for MM and potentially for other solid malignancies treated with ICPI therapy.

    Conflict of Interest:
    None declared.