{Reference Type}: Journal Article
{Title}: Divergent Cellular Expression Patterns of PD-L1 and PD-L2 Proteins in Breast Cancer.
{Author}: Jorns JM;Sun Y;Kamaraju S;Cheng YC;Kong A;Yen T;Patten CR;Cortina CS;Chitambar CR;Rui H;Chaudhary LN;
{Journal}: J Pers Med
{Volume}: 14
{Issue}: 5
{Year}: 2024 Apr 29
{Factor}: 3.508
{DOI}: 10.3390/jpm14050478
{Abstract}: PD-L1 immunohistochemistry (IHC) has become an established method for predicting cancer response to targeted anti-PD1 immunotherapies, including breast cancer (BC). The alternative PD-1 ligand, PD-L2, remains understudied but may be a complementary predictive marker. Prospective analysis of 32 breast cancers revealed divergent expression patterns of PD-L1 and PD-L2. PD-L1-positivity was higher in immune cells than in cancer cells (median = 5.0% vs. 0.0%; p = 0.001), whereas PD-L2-positivity was higher in cancer cells than immune cells (median = 30% vs. 5.0%; p = 0.001). Percent positivity of PD-L1 and PD-L2 were not correlated, neither in cancer cells nor immune cells. Based on a cut-point of ≥1% positivity, ER+ tumors (n = 23) were frequently PD-L2-positive (73.9%), whereas only 40.9% were PD-L1-positive. These data suggest differential control of cellular PD-L1 and PD-L2 expression in BC and a potential role for PD-L2 IHC as a complementary marker to PD-L1 to improve selection of aggressive ER+ BC that may benefit from anti-PD-1 therapy.