The goal of this observational study is to evaluate and validate the expression and prognostic value of 15 ADC-targetable membrane proteins (PSMA, B7-H3, STEAP1, TROP2, KLK2, HER2, TF, HER3, DLL3, SEZ6, STEAP2, MUC1, NECTIN4, FAP, PDL1) in patients with diverse clinicopathological subtypes of prostate cancer (e.g. primary and different metastatic types，HSPC and CRPC， PC with neuroendocrine differentiation, cribriform/intraductal carcinoma).

The main questions it aims to answer are:

1. What is the expression profile of 15 clinically actionable targes in tumor tissues from patients with diverse clinicopathological subtypes of prostate cancer?
2. Can the prognostic value of these targets (e.g. association with overall survival) identified in a retrospective cohort be validated in an independent prospective cohort? Researchers will head-to-head compare the expression levels among different targets and across different disease stages/metastatic site. Researchers will also assess whether the targets showing prognostic significance in the retrospective cohort can also predict survival outcomes in the prospective cohort.

Participants in the retrospective cohort have already provided archived tissue samples and clinical data. Participants in the prospective cohort (metastatic prostate cancer patients) will be invited to provide residual tumor tissue samples obtained during standard care and will be followed up regularly for clinical outcomes.

1. Study Type This is a single-center, observational cohort study incorporating both retrospective and prospective components. It is a non-interventional study that does not involve assignment of participants to specific interventions.
2. Objectives

Primary Objectives:

1. To determine the protein expression profile (positive rate, expression level) of 15 membrane targets (PSMA, B7-H3, STEAP1, TROP2, KLK2, HER2, TF, HER3, DLL3, SEZ6, STEAP2, MUC1, NECTIN4, FAP, PDL1) in diverse clinicopathological subtypes of prostate cancer (HSPC and CRPC，primary and metastatic lesions include lymph node, bone and visceral metastasis, etc.).
2. To characterize the molecular subtypes of prostate cancer based on the expression profiles of AR, PSA, PSMA, Syn, CgA, CD56, p53, RB1, and PTEN across different disease states and metastatic sites.
3. To validate the association between the expression of prognostically significant targets (identified in the retrospective cohort) and overall survival (OS) in an independent, prospectively enrolled cohort of prostate cancer patients.

Secondary Objectives:

1. To compare the expression of each target between matched CSPC and mCRPC samples from the same patients.
2. To compare the expression of each target across different metastatic sites (e.g., bone, lymph node, viscera) in mCRPC.
3. To analyze the association between target expression and clinical outcomes [biochemical recurrence-free survival (BFS), metastasis-free survival (MFS)] in patients with CSPC.
4. To explore co-expression patterns of the targets and their correlation with clinicopathological features.

3.Study Design

Retrospective Cohort:

Population: Patients treated at Peking University First Hospital between 2000-2025.

Cohort 1: Primary Tumor Cohort - This cohort includes patients with CSPC or CRPC, or those with special pathological structures, for whom primary tumor tissue (from biopsy or surgery) is available.

Cohort 2: Lymph Node Metastasis Cohort - This cohort includes patients with CSPC or CRPC for whom lymph node metastasis tissue is available (from biopsy or surgery) .

Cohort 3: Bone Metastasis Cohort - This cohort includes patients with CSPC or CRPC, for whom bone metastasis tissue is available (from biopsy or surgery).

Cohort 4: Visceral Metastasis Cohort - This cohort includes patients with CSPC or CRPC, for whom visceral (e.g., liver, lung) metastasis tissue is available.

Procedures: Archived FFPE tissue blocks will be retrieved for immunohistochemistry (IHC) staining. Clinical and follow-up data will be extracted from medical records.

Prospective Cohort:

Population: Newly diagnosed metastatic prostate cancer patients at Peking University First Hospital from January 1, 2026.

Cohort 5: Prospective Validation Cohort - This cohort will consist of patients with metastatic prostate cancer (mHSPC or mCRPC), from whom tissue samples will be collected prospectively along with their clinical data.

Procedures: Eligible patients will provide informed consent. Residual tumor tissue obtained during standard-of-care biopsies or surgeries will be collected for IHC staining. Patients will be followed prospectively at defined intervals to collect treatment and outcome data.

4.Methods Laboratory Assessment (for both cohorts): IHC will be performed on FFPE tissue sections using validated antibodies against the eight targets (as specified in the protocol: e.g., HER2: ab2142275; TROP2: ab214488; etc.). Staining will be evaluated by pathologists blinded to clinical outcomes. IHC score 0-3,0=negative/none,1=weak,2=moderate,3=strong. A modified H-score ([1×% weak staining + 2×% moderate staining + 3×% strong staining], range 0-300) will be used for quantification.

Data Collection: Clinical data (demographics, laboratory assessment (tPSA、LDH levels)，imaging data(ultrasound, MRI, CT, PET, providing TNM staging results, treatment history, pathology reports) and outcome data (biochemical recurrence, metastasis, death) will be collected retrospectively from databases/records for the retrospective cohort and prospectively during follow-up visits for the prospective cohort.

Inclusion Criteria:

• For the Retrospective Cohorts (mCRPC, CSPC, Special Pathology):

  1. Patients with a pathological diagnosis of prostate cancer.
  2. Treated at Peking University First Hospital between January 2000 and 2025.
  3. Availability of adequate, qualified formalin-fixed, paraffin-embedded (FFPE) tumor tissue blocks for research.
  4. Availability of essential clinical and follow-up data in medical records.

• For the Prospective Cohort:

  1. Age ≥ 18 years.
  2. CSPC, primarily includes patients who underwent neoadjuvant therapy and have paired pre- and post-treatment biopsy and surgical specimens; or patients with special clinicopathological subtypes.
  3. metastatic prostate cancer patients.
  4. Planned or recent (within 6 months prior to enrollment) acquisition of tumor tissue (from metastasis or primary site) as part of standard clinical care, with sufficient residual tissue available for the study.
  5. Willing and able to provide written informed consent.

Exclusion Criteria:

• For All Cohorts:

  1. Tumor tissue sample is of insufficient quality or quantity for immunohistochemical (IHC) analysis.
  2. Essential clinical or outcome data are missing or irretrievable, which would preclude meaningful analysis.

• Specifically for the Prospective Cohort:

  1. Any condition that, in the investigator's judgment, would significantly compromise the patient's ability to provide informed consent or comply with the study follow-up procedures.
  2. Patient refusal to participate.

1. Retrospective Cohorts: These four groups are defined by the origin of the archived tumor tissue specimen at Peking University First Hospital (2000-2025). Each cohort includes patients across the spectrum of disease states (castration-sensitive [CSPC] and castration-resistant [CRPC] prostate cancer) and those with special clinicopathological subtypes (e.g., neuroendocrine differentiation, cribriform/intraductal carcinoma).
2. Prospective Validation Cohort: This group will consist of patients with metastatic prostate cancer recruited at Peking University First Hospital starting January 1, 2026. Participants will provide informed consent for the use of residual tumor tissue (from any anatomic site) obtained during standard clinical care and for prospective clinical follow-up.

The core material for analysis is formalin-fixed, paraffin-embedded (FFPE) tumor tissue from all participants, which will be subjected to immunohistochemical (IHC) staining for biomarker evaluation.