
Breast cancer refers to the most common malignancy in women. Its incidence rate ranks first among female malignancies, and it has been elevating (1). With the rise in the new patients and the potential variations in the molecular phenotype and genotype of breast cancer, a more efficient culture system maintaining the biological characteristics of breast cancer
Tumor-like organ culture refers to a cross-concept accompanying the development of organoids and oncology, namely, tumor cells form microstructures similar to the source tumor tissue structure and gene expression lineage under appropriate culturing conditions, which can reveal the biology of the source tumor tissue. It acts as an effective model to study tumors and high-throughput screening drugs
Cells exhibit a three-dimensional growth pattern in the body. Under conventional two-dimensional planar culture conditions, the cells are gradually flattened, losing some of their biological characteristics in the body; Thus, a low degree of reduction of the results of
Breast organoids act as vital branches of tumor organoids, whereas the construction of the culture system has long been explored and optimized to form an organoid culture system that exhibits common characteristics with other tumor organoids as well as targets breast cancer cell characteristics. The construction of breast cancer organoids primarily consists of three elements (i.e., breast cancer cells, stroma and cytokines).
This series of characteristics can act as an indicator of non-invasive monitoring of drug sensitivity variations in individual patients.
The matrix forming and maintaining the growth of organoids is a critical substance that mimics the microenvironment in the body. It creates attachment points for cells to support it, while providing nutrients to maintain cell growth. The common types include rat tail collagen, collagen and matrigel. Rat tail collagen is the earliest used matrix, which is easy to obtain and can support higher and cell survival rates. Since then, collagen and other matrices have been extensively used.; Among them, collagen IV, the major component of tumor stroma and laminin, is isolated from sarcoma and forms the main component of matrigel, which refers to the most used commercial matrix gel. Together with various growth factors, it forms a matrix protein mixture, which can more effectively replace the extracellular matrix and promote the growth, differentiation and tissue formation of breast cancer cells (22).
To achieve long-term
Table 1 . The cytokines of cultural system and recommend concentration
Cytokines | Function | Concentration |
---|---|---|
Epidermal Growth Factor, EGF | The ligand of epidermal growth factor receptor (EGFR) promotes the proliferation of breast cancer epithelial cells by promoting cell mitosis, to achieve the purpose of maintaining organoid growth for a long time | 0.1∼10 ng/ml |
Fibroblast Growth Factor7, FGF7 | Promoting the growth of epithelial cells; Improving the ability of breast cancer cells invades and metastasizes; working with Wnt3a to promote the formation of spheroid structures in the directionally differentiated endoderm and further expand the formation of breast cancer organoid | 50 ng/ml |
Wnt3a | Lipoprotein receptor-related protein (LPR) ligand, which mainly regulates tumor cell proliferation and differentiation | 50∼500 ng |
Noggin | Bone morphogenetic protein (BMP) inhibitors, which can replace the missing Niche-related signaling molecules to promote stem cell proliferation, increase the number of initial organoid formation, and accelerate the rate of expansion | 100 ng/ml |
R-Spondin-1 | G protein-coupled receptor 4/5 (LGR4 / 5) ligand, a Wnt pathway agonist, which riches in leucine repeats, can maintain stem cell population growth for a long time in vitro | 500 ng/ml |
Neuregulin1 | Neuregulin1:EGF receptor tyrosine kinase 3 and 4 (ERTK3 / 4) ligands are involved in breast formation and tumorigenesis | 100 g/l |
Y-27632 | Y-27632:Rho-related coiled-coil formation protein kinase (ROCK) inhibitors can effectively reduce the apoptosis of stem cells during the process of culture and improve the state of the medium | 10 mM |
A83-01 | Tumor growth factor- | 1 |
SB202190 | MAPK inhibitor that promotes the stability of pluripotent stem cells | 1 |
Organoid functions effectively reflect tumor heterogeneity, and gene sequencing of organoids formed in culture reveals that most organoid functions can display genes of source tissues well, even after prolonged passage, organoids and primary tumors are mutated. The similarity of characteristics and gene profile expression can reach 60% or more (28). Moreover, breast cancer organoids present all subtypes of solid tumors, which can be used as an effective
The selection of tumor drugs and treatment options determines the prognosis of patients, and the heterogeneity of tumors determines the precision of individualized medicine to enhance the treatment effect for specific patients. Both the cell phenotype and tissue structure of breast cancer organoids can indicate the biological characteristics of solid tumors in patients. Moreover, as the three-dimensional culture system of breast cancer organoids has been built and optimized progressively, the organoid functions of batch culture can affect multiple drugs simultaneously. By screening, individualized treatment options can be quickly and accurately obtained. In contrast to the two-dimensional planar cell culture system of breast cancer organoids, the assessed results of the drug efficacy are closer to the actual effect. The results of the sensitivity of different clinical drug regimens can be visually presented. Several studies reported the assessed sensitivity up to 100%, the specificity of 93%, and the positive rate of 88% (31). Cassidy et al. (32) used breast cancer organs to screen out 18 anticancer drugs; they found that the inhibition rate of pemetrexed combined with carboplatin, gemcitabine and pirlotinib was 60% more than those of other regimens. When this method is used in specific patients, the efficacy will be higher than the recommended standard treatment. The breast cancer organoids produced by Her2 over-expressed tissues are susceptible to tamoxifen. Under the concentration of the drug over 1
Gene mutations critically lead to the formation of breast cancer, and different patients, different pathological types and even the identical disease type show differences in gene expression. Besides, targeted drugs targeting different mutation subtypes are vital to treatment. In the cytokine-added medium, stem cells can exhibit other genotypes if the original tissues are not differentiated. Nearly 90% of biopsies of one patient contain all the differentia-ted genotypes. Thus, it is of high significance value to study the association between breast cancer tissue genotype and anticancer drugs
Besides the use of breast cancer organs for high-throughput screening of drugs and personalized treatment based on breast cancer gene profiles, it has also been extensively adopted in toxicology -under the development of novel drugs. New drugs developed for breast cancer are commonly tested for their effects and safety on animal models. In the case of little effect of drugs, they are usually treated by expanding the types or doses of anticancer drugs. Accordingly, drug accumulation often adversely affects patients’ livers. Kidney function generates `toxic side effects. Weeber et al. (35) exploited-breast cancer tissue-derived organoids to continuously controlthe dose and compatibility of various drugs before novel drugs were adopted to treat breast cancer patients. Such application solves the excessive abuse and limitation of animal models in the development of novel drugs, which - shortens the time required for drug detection to satisfy the standards and also creates ideas to deal with excessive anticancer drugs in clinical treatment.
After the initial success of immunotherapy in melanoma, researchers in oncology have shifted their emphasis to their respective research directions. Co-culture of tumor organoids are derived from colorectal cancer (CRC) and non-small cell lung cancer (NSCLC) and peripheral blood lymphocytes of corresponding patients. After two tweeks of co-cultivation, the tumor organoids are recognized, presented and then processed -with the immune system as new organisms,; Subsequently, the patient’s immune response is started. 50% of autologous tumor organoids enrich the CD8+ T natural killer cells in the peripheral blood of patients, as well as promoting the secretion of IFN
The
With the advent of advanced imaging technologies (e.g., optical metabolic imaging (OMI), the time of using organoids to determine the effectiveness of treatment options can be reduced to 72 h, and the invalid scheme of organoids can be more accurately identified, so as to avoid patients having received excessive treatment (41).
In response to the problem of low cell content in tumor tissue, we can use multi-point biopsy. For experimental differences caused by different product batches and inconsistent schemes in the culture system, we can adjust matrigel by adding collagen protein composition, so the same substrate is applied in independent experiments to ensure the repeatability of the experiment (14). Moreover, Besides, recent studies have continuously pointed out that we can solve the shortcomings of single organoid system components by adding other cells to form a “co-culture” system. Dijkstra et al. (36) employed the patient’s tumor-like organs to activate T lymphocytes to amplify the patient’s immune function. The results of their experiment provide novel insights into the study on breast cancer immuno-therapy. Moreover, the continuous advancement of microfluidic technology and new equipment will further expand the application scenarios and enhance the efficiency of tumor organoids.
In the conventional cell models, oxygen, nutrients, metabolities and signaling molecules can be used infinitely, however, the cancer cells in the body have limited utilization of various substances due to the three-dimensional structure of the tumor mass, consequently, causing various degrees of influence on the expression of cancer cell molecules and biological behaviors. Besides, patient-derived xenografts cannot be screened for high-throughput of drugs. Compared with the above models, organoids are easy to be cultured, and involve the advantages of cell models and PDX. Therefore, it has become the first choice for emerging breast cancer in a short time of research models
Although breast cancer organoids are widely used, there are still apparent deficiencies, such as: lack of mesenchymal cells, nerves, blood vessels, and immune system. The model that is constituted by single breast cancer is still quite different from the solid tumor in terms of tumor heterogeneity. The relating studies have continuously pointed out that we can form a “co-culture” system by adding corresponding cell components to restore the “tumor microenvironment” to a certain extent, for instance: lymphocytes andfibroblasts, to achieve the purpose of highly reproducing solid tumors
Breast cancer organoids can not only explore the role of tumor stem cells, so that we can study the occurrence, development and driving factors of tumors from normal cells, invasive cancers to metastatic cancers; but used to the chemotherapy, combined with gene editing technology to interfere with the progress of breast cancer, assessment of drug toxicity and immunotherapy autologous transplantation. Organoids can be generated from surgical samples, as well as from endoscopic fine needle aspiration samples. Thus, the model is capable of summarizing various disease stages and clinical conditions. Moreover, organoids can be generated from a small amount of tissue and completed efficiently, which can be employed for drug testing and assessment of potential diagnostic biomarkers; they can also verify multiple drivers of tumor progression
The authors have no conflicting financial interest.
Conceptualization: Jin Yu, Wei Huang
Investigation: Jin Yu
Resources: Jin Yu
Supervision: Jin Yu
Writing – original draft: Jin Yu, Wei Huang
Writing – review & editing: Jin Yu
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