Exploring the Expression Level of Cadherin 6 Protein (CDH6) in Primary Malignant Bone Tumor Specimens and Its Clinical Application in Prognosis Assessment

1. Evaluate the feasibility of using immunohistochemistry to detect the expression level of CDH6 in histological white slides of patients with osteosarcoma and Ewing's sarcoma as a biological marker for prognostic monitoring The patient's initial visit was clinically diagnosed as high-grade osteosarcoma or Ewing's sarcoma. The informed consent form for specimen monitoring was signed first. During the puncture biopsy, fresh tissue (soft tissue component, not bone tissue) with a volume of about 1cm3 was taken, fixed with formalin solution, and tissue slices (white slices) with a thickness of 5 microns were cut, smeared, and baked. Immunohistochemistry staining was used for CDH6 expression analysis (XP) ® Cadherin-6 (D3T3I) Rabbit mAb Cat:#48111, CellSignaling Technology）。 2. Treatment process and follow-up The routine neoadjuvant chemotherapy regimen for osteosarcoma in our center includes sequential use of cisplatin, high-dose doxorubicin, methotrexate, and ifosfamide, while the VDC-IE regimen is used for Ewing sarcoma (see Figure 3.1.1A, B for details). Due to the significant heterogeneity of osteosarcoma cells, the subpopulations of cells affected by each drug are not the same, and there are also differences in the subpopulations of necrotic and lysed cells after medication. The expression level of CDH6 in patient tissue slices will dynamically change with the sensitivity of chemotherapy. While conducting clinical evaluations, if given the opportunity, we will try to compare the changes in CDH6 levels in tissue sections to assess their value for efficacy monitoring. Patients usually undergo surgical treatment after neoadjuvant chemotherapy, and the tumor burden decreases sharply after surgery. The gross tumor specimen obtained during surgery should be retained with qualified tumor tissue samples (at least 1cm3 in volume). During the tumor treatment process, if there is an opportunity for surgery, biopsy or resection of tumor tissue should be performed again to