Dual-Target CAR-NK Cells for Advanced Breast Cancer (HER2+ and TNBC)

Inclusion Criteria: * Histologically confirmed breast carcinoma that is locally advanced, unresectable, or metastatic. * Disease subtype: HER2-positive breast cancer or triple-negative breast cancer (TNBC). * Progression after, intolerance to, or ineligibility for standard therapies appropriate for the disease subtype and line of therapy. * At least one measurable lesion per RECIST v1.1. * Tumor antigen assessment available (fresh or archival): expression of at least one candidate target antigen (HER2/ERBB2, MUC1, or ROR1). For TNBC, mesothelin assessment may be performed for exploratory analyses. * ECOG performance status 0-1. * Adequate organ function (example thresholds): ANC ≥ 1.0 x 10\^9/L; platelets ≥ 75 x 10\^9/L; hemoglobin * 8 g/dL; AST/ALT ≤ 3x ULN (≤ 5x with liver metastases); total bilirubin ≤ 1.5x ULN; creatinine clearance * 50 mL/min. * Left ventricular ejection fraction (LVEF) ≥ 45% and no uncontrolled cardiac arrhythmia. * Negative pregnancy test for participants of childbearing potential; agreement to use effective contraception during study treatment and for 6 months after last CAR-NK infusion. * Ability to understand and willingness to sign informed consent. Exclusion Criteria: * Active, untreated central nervous system (CNS) metastases or leptomeningeal disease. Patients with treated CNS metastases may be eligible if clinically stable for ≥ 4 weeks and off high-dose steroids. * Prior gene-modified cellular therapy (e.g., CAR-T or CAR-NK) within 6 months or unresolved grade ≥ 2 toxicity from prior cellular therapy. * Clinically significant active autoimmune disease requiring systemic immunosuppression (physiologic steroid replacement permitted). * Uncontrolled infection, including uncontrolled HBV, HCV, or HIV infection (controlled infections may be eligible per investigator). * History of severe hypersensitivity to fludarabine or cyclophosphamide. * Pregnant or breastfeeding. * Concurrent participation in another interventional study that could confound safety or efficacy assessments. * Any condition that, in the investigator's judgment, would make the participant unsuitable for the study (e.g., uncontrolled comorbidity, inability to comply with protocol procedures).