New drug development is a complex process that typically takes ten years or even longer from the discovery of lead compounds to clinical application. Traditional drug screening mainly relies on 2D cultured cell models, but 2D cultured cells have certain limitations in drug efficacy evaluation ^[1]. Patient derived organs (PDO), as a new tool for studying tumors, have unique advantages in the development and screening of tumor drugs, as they not only retain the original biological characteristics of tumors but also have stable passage. In addition, organoids have been recognized by Science as one of the top ten technologies of the year, becoming a powerful tool in fields such as new drug research and development, precision therapy, and regenerative medicine.

Creating a Tumor Organoid Biobanks

Organoids are a three-dimensional culture system generated by embryonic stem cells, induced pluripotent stem cells, and adult stem cells. They provide a good platform for studying organ development and simulating pathological processes. At present, organoid biobanks derived from various cancers have been established for research on tumor immunotherapy (Fig 2).

Tumor organoid biobanks are generated in two ways: collecting tissue directly from patients through biopsy or surgical resection; modifying organoids derived from healthy tissues^[3][4][5]. The tumor organoid biobanks allow for the passage, amplification, and cryopreservation of organoids from different cancers and different lesions, grades, or stages of designated cancers.

Tumor Organoid Biobanks for Active Drug Screening

The first step in drug development is the screening of active compounds, and the same applies to tumor organoids. Researchers have identified a novel candidate drug MCLA-158 through functional screening using a library of organoid biological samples from CRC patients.

Researchers extracted and stored 61 primary CRCs and 11 CRC liver metastasis organoids from a total of 99 tumor samples from 68 patients at two different hospitals. They also selected healthy mucosa adjacent to the tumor to establish organoids and constructed an organoid living organism biobank from CRC patients (Fig 3). Secondly, drug screening was conducted on over 500 bispecific antibodies using this type of organ organ biobank, and their activity was evaluated in matched normal colon mucosal organs. It was ultimately found that MCLA-158 (EGFR x LGR5 bispecific antibody) can bind to epidermal growth factor receptor (EGFR) and leucine rich G-protein coupled receptor-5 (LGR5). It effectively inhibited the growth and metastasis of colorectal cancer organoids in vitro and in vivo^[7].

In tumor immunotherapy, the interaction between tumor and immune cells in the tumor microenvironment (TME) is crucial for preclinical evaluation. Without the input of the tumor microenvironment, it is impossible to accurately evaluate the potential drug efficacy in the immunotherapy^[9]. After multiple studies on co-culture of tumor organoids and autologous peripheral blood lymphocytes, it has been found that a sufficient number of tumor specific T cells are essential for immunotherapy in tumor organoid models^[10]. If mouse chicken ovalbumin peptide (OVA) specific T cells, human NY-ESO-1 specific CD8⁺ T cells, and autologous tumor infiltrating T cells are co-cultured, they can promote tumor recognition and high cytotoxicity^[11]. Therefore, in order to make tumor organoids closer to the living tumor microenvironment, other cells can be added to the culture system to establish a cell co-culture system.

The research group of Professor Xiongbin Lu from Indiana University in the United States reported on the screening of epigenetic inhibitors based on organoids. Co-culture of breast tumor organoids derived from mice or cancer patients with tumor specific cytotoxic T cells (CD8⁺ T cells) to better simulate the tumor microenvironment in mice (Fig 4). After drug screening, three epigenetic inhibitors were selected from 141 epigenetic related compounds that can promote antigen presentation and enhance T cell mediated cytotoxicity^[12].

Literature process (for reference):

The orthotopic transplantation generates tumor tissue in vivo → Tumor tissue is digested into individual cells for 2D culture → Collection of adherent cells for organoids culture → Tumor organoids screening → 48 hours of drug treatment for tumor organoids → Co-culture of drug-treated organoids with OVA specific CD8⁺T cells^[13].

In addition to active drug screening and cytotoxicity testing, tumor organoids derived from patients can also provide reliable tumor models in vitro for precision medicine^[14][15]. More and more evidence confirms that the phenotype and genotype are consistent between the original tumor tissue and the generated tumor organoids^[16][17]. Meanwhile, clinical studies have shown that tumor organoids have a high success rate in predicting the clinical response of individual patients to the treatment of colorectal cancer and gastroesophageal cancer^[18][19][20]. But currently, drug testing based on tumor organoids still takes weeks or even months to provide results to patients.

The Yawei Hu team at Tsinghua University has developed an integrated superhydrophobic microwell array chip (InSMAR-chip) for high-throughput three-dimensional cultivation and analysis of lung cancer organoids (LCOs), and the response of LCOs to anticancer drugs is consistent with clinical results and gene mutations. Therefore, the combination of LCOs and InSMAR-chip may provide an effective means for quickly predicting specific drug responses in lung cancer patients (Fig 5).

In addition, the FDA approved the world's first new drug (NCT04658472) based solely on preclinical data obtained from "organoid chip" research to enter clinical trials in 2022. This means that the "organoids chip" experiment has replaced traditional animal experiments for the first time and has been officially recognized.

Literature process (for reference):

1. A mechanical sample processing method was established to generate a sufficient number of LCOs from the patient's tumor tissue within 3 days.

2. Remove the tumor tissue from surgically resected (approximately 0.5 × 0.5 × 0.5 cm³) into small pieces with scissors, gently grind, and then push them into a 100 µm filter using a syringe.

3. Collect 40~100 µm tumor fragments with a 40 µm filter, suspend and culture overnight in an optimized LCO medium.

4. Inoculate LCOs in Matrigel matrix gel and continue to culture in porous plates for 3 days for long-term amplification and organoid identification, or conduct a 3-day drug sensitivity test on InSMAR chip^[21].

By establishing tumor organoid models and tumor organoid biobanks, drugs can be evaluated for anti-tumor activity, toxicity, drug targets, and drug sensitivity screening. Tumor organoids can also be applied to precision medicine and preclinical drug prediction, and timely selection of appropriate treatment plans for patients. Therefore, organoid models and screening platforms will help to better understand disease mechanisms, test and develop new drugs related to diseases.