A clinical evaluation of an ex vivo organ culture system to predict patient response to cancer therapy

Abstract

Introduction: Ex vivo organ cultures (EVOC) were recently optimized to sustain cancer tissue for 5 days with its complete microenvironment. We examined the ability of an EVOC platform to predict patient response to cancer therapy.

Methods: A multicenter, prospective, single-arm observational trial. Samples were obtained from patients with newly diagnosed bladder cancer who underwent transurethral resection of bladder tumor and from core needle biopsies of patients with metastatic cancer. The tumors were cut into 250 μM slices and cultured within 24 h, then incubated for 96 h with vehicle or intended to treat drug. The cultures were then fixed and stained to analyze their morphology and cell viability. Each EVOC was given a score based on cell viability, level of damage, and Ki67 proliferation, and the scores were correlated with the patients' clinical response assessed by pathology or Response Evaluation Criteria in Solid Tumors (RECIST).

Results: The cancer tissue and microenvironment, including endothelial and immune cells, were preserved at high viability with continued cell division for 5 days, demonstrating active cell signaling dynamics. A total of 34 cancer samples were tested by the platform and were correlated with clinical results. A higher EVOC score was correlated with better clinical response. The EVOC system showed a predictive specificity of 77.7% (7/9, 95% CI 0.4-0.97) and a sensitivity of 96% (24/25, 95% CI 0.80-0.99).

Conclusion: EVOC cultured for 5 days showed high sensitivity and specificity for predicting clinical response to therapy among patients with muscle-invasive bladder cancer and other solid tumors.

Keywords: cancer; clinical response; ex vivo organ culture; prediction of treatment response; solid tumors.

Figure 1

An ex vivo organ culture (EVOC) system for preservation of the cancer microenvironment. (A) Colorectal cancer (CRC), transitional cell carcinoma (TCC) and breast cancer (BC) were cultured in an EVOC assay that preserves the tumor microenvironment. Representative images of the tissues are shown on Day 0 – when the tissue was received and after 5 days in culture. Hematoxylin and eosin (H&E) and Ki67 staining are shown. (B,C) Viability and proliferation of the different cancer samples were compared between Day 0 and Day 5 (N = 5 per cancer type). Cancer viability and Ki67% stain was assessed and quantified by a pathologist showing non-significant changes during the culture period (N = 16). (D) The capacity for signal transduction modification was assessed by adding specific pathway inhibitors and determining their effect after 24 h. Trametinib, a pERK inhibitor, palbociclib, a CDK4/6 inhibitor and NT219, a pStat3/insulin receptor substrate (IRS) inhibitor were added to the culture and their respective pathway targets were stained by immunohistochemistry showing downregulation of activity in the culture system.

Figure 2

Correlation between EVOC scores and clinical response of patients with MIBC. (A) EVOC scores were computed for each sample treated with cisplatin alone, gemcitabine alone and combined cisplatin and gemcitabine. The average is marked with an X while median is denoted by a horizontal line (B) Using an EVOC score of 45 to differentiate between non-response and response we found that 75.6% of patients with MIBC who had an EVOC score were classified as responders while 24.4% were classified as non-responders. (C) The clinical outcomes (pathology or RECIST) of patients who received a full course of cisplatin and gemcitabine were correlated to their EVOC score. EVOC scores are listed next to the four patients who were found to be non-responders (red) and the twelve patients identified as responders (blue). Patients who underwent cystectomy were listed as non-responders (NR), partial responder (PR), and complete responder (CR) based on pathology, while tumors of patients who were evaluated by imaging alone were designated a RECIST score [progressive disease (PD), stable disease (SD), PR, or CR]. (D) Representative H&E images from a responder and non-responder patient with bladder cancer. Vehicle samples were compared to samples treated with cisplatin and gemcitabine for 5 days.

Figure 3

Use of the EVOC system to assess treatment response on biopsies. (A) Biopsies of breast cancer (BC), pancreatic ductal adenocarcinoma (PDAC) and scarcoma were obtained prior to initiation of patient treatment and maintained in EVOC for 5 days. Representative images of the biopsies on day 0 and day 5 show high viability and preservation during the culture assay of several prominent tissue types. (B) Representative images of a pancreatic cancer biopsy stained with hematoxylin & eosin comparing treatment with vehicle and treatment with combined paclitaxel and gemcitabine after 5 days. The sample treated with paclitaxel and gemcitabine shows cell-death representing a response and an EVOC score of 62. (C) A graph demonstrating the percent of each cancer type obtained in the clinical trial evaluating EVOC predictive capabilities on biopsies. (D) Correlation between EVOC scores and clinical outcomes of patients. Cancer types included pancreatic, breast, colorectal, esophageal, sarcoma, and liver cancer N = 18.

Figure 4

Prediction of clinical response using EVOC scores of all collected samples. (A) The distribution of responders and non-responders based on an EVOC score of 45. (B) Computation of predictive statistical calculations for sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). (C) Correlation between EVOC scores and clinical outcomes of patients (determined by pathology or RECIST) with resected or biopsy samples (N = 34).