SHANGHAI – Several weeks ago a 21-year-old man named Wei Zexi, diagnosed with terminal synovial sarcoma, a rare form of cancer of the soft tissue, died. In the weeks since his death, public debate and outrage have hit upon various elements of his story, illustrating a volatile mix of distrust in online transparency, lax oversight of regulations governing cell treatments and commonplace greed. It is also giving immunotherapy, a promising form of cancer treatment, a bad reputation in China.