PD-L1-expressing cancer-associated fibroblasts induce tumor immunosuppression and contribute to poor clinical outcome in esophageal cancer.

The programmed cell death 1 protein (PD-1)/programmed cell death ligand 1 (PD-L1) axis plays a crucial role in tumor immunosuppression, while the cancer-associated fibroblasts (CAFs) have various tumor-promoting functions. To determine the advantage of immunotherapy, the relationship between the cancer cells and the CAFs was evaluated in terms of the PD-1/PD-L1 axis. Overall, 140 cases of esophageal cancer underwent an immunohistochemical analysis of the PD-L1 expression and its association with the expression of the α smooth muscle actin, fibroblast activation protein, CD8, and forkhead box P3 (FoxP3) positive cells. The relationship between the cancer cells and the CAFs was evaluated in vitro, and the effect of the anti-PD-L1 antibody was evaluated using a syngeneic mouse model. A survival analysis showed that the PD-L1+ CAF group had worse survival than the PD-L1- group. In vitro and in vivo, direct interaction between the cancer cells and the CAFs showed a mutually upregulated PD-L1 expression. In vivo, the anti-PD-L1 antibody increased the number of dead CAFs and cancer cells, resulting in increased CD8+ T cells and decreased FoxP3+ regulatory T cells. We demonstrated that the PD-L1-expressing CAFs lead to poor outcomes in patients with esophageal cancer. The cancer cells and the CAFs mutually enhanced the PD-L1 expression and induced tumor immunosuppression. Therefore, the PD-L1-expressing CAFs may be good targets for cancer therapy, inhibiting tumor progression and improving host tumor immunity.

[Two Cases of Stevens-Johnson Syndrome after Nivolumab Therapy for Gastric Cancer].

Case 1: A 51-year-old man with advanced gastric cancer and peritoneal metastasis was referred to our hospital. He received fourth-line chemotherapy with nivolumab, but it became PD. Next, he received S-1 plus docetaxel therapy as fifth- line therapy. After 2 courses of S-1 plus docetaxel, erythema and blisters appeared on his limbs, with erosions of the oral mucosa and penis. We diagnosed Stevens-Johnson syndrome(SJS)based on the clinical and pathological findings. He received steroid treatment, but the cutaneous symptoms persisted; therefore, it was impossible to continue the chemotherapy because of the SJS. Case 2: A 75-year-old woman with recurrence of peritoneally disseminated gastric cancer received third-line chemotherapy with nivolumab. After 1 course of nivolumab, erythema appeared on her body and limbs, with erosion of the lips and oral mucosa. We diagnosed SJS based on the clinical findings. She received steroid treatment, but the cutaneous symptoms persisted; therefore, it was impossible to continue chemotherapy because of the SJS. It should be noted that the onset of serious irAEs, such as SJS, might make continuous chemotherapy difficult.