RecruitingPhase 1Biological interventionUmbilical Cord Blood Megakaryocyte Injection (XJ-MK-002) for Cancer Therapy-Induced Thrombocytopenia (CTIT)This study is a single-center, open-label, single-arm, dose-escalation clinical trial to assess safety \& tolerability of XJ-MK-002 in CTIT patients. It plans to recruit subjects aged 18 to 75 years old with chemotherapy-induced thrombocytopenia (CTIT). The study is designed with three dose levels: low dose (1.0×108 viable cells per person), medium dose (3.0×108 viable cells per person), and high dose (6.0×108 viable cells per person). The first dose group (low dose) will enroll one subject for accelerated titration, while the other two dose groups will enroll at least three subjects each. Subjects successfully enrolled will receive only one cell therapy session. After the cell therapy, they will undergo a 28-day dose-limiting toxicity (DLT) observation period.