Case Report: Complete response to four cycles of camrelizumab in a PD-L1 negative patient with advanced oral squamous cancer - He, Jianqiao; Yu, Guoning; Ma, Yi; Shi, Xiaoqiong; Gao, Yingna; Zheng, Hongliang; Zhu, Minhui; Zhang, Caiyun (Frontiers in Immunology, 2025)