A CRISPR/Cas9-Engineered ARID1A-Deficient Human Gastric Cancer Organoid Model Reveals Essential and Nonessential Modes of Oncogenic Transformation

Combinatorial Analysis of AT-Rich Interaction Domain 1A and CD47 in Gastric Cancer Patients Reveals Markers of Prognosis

Background: The AT-rich interaction domain 1A (ARID1A) is thought to be a tumor suppressive gene, and most of its mutations result in loss of expression of ARID1A protein. Combined with SIRPα on the surface of macrophages, CD47 on the surface of cancer cells can send an antiphagocytic "Don't eat me" signal to the immune system that helps to avoid immune surveillance. However, the relationship between ARID1A and CD47 expression and their prognostic value in gastric cancer (GC) are still unknown. Methods: In this study, we evaluated ARID1A and CD47 expression in 154 GC patients' tissues using tissue microarray. Expressions of ARID1A and CD47 in GC cell lines were determined by western blot and quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) techniques, and cell membranous CD47 expression was quantified by flow cytometry. In addition, chromatin immunoprecipitation (ChIP)-qPCR was used to determine the aspects of regulation of CD47 by ARID1A. The proportions of tumor-infiltrating immune cells were estimated on The Cancer Genome Atlas (TCGA) data set by using quanTIseq and EPIC algorithms. The infiltration of M1-polarized macrophages, M2-polarized macrophages, and regulatory T cells (Tregs) in GC tissues was determined by multispectral immunofluorescence. Results: A significant correlation was found between loss of ARID1A and high expression of CD47 at protein level in GC. By integrating 375 bulk RNA sequencing samples from TCGA data set, we found that mutated ARID1A correlated with high CD47 expression. In GC cell lines, knockdown of ARID1A significantly increased CD47 expression both at protein and mRNA levels as measured by western blot, qRT-PCR, and flow cytometry. Moreover, ChIP-qPCR revealed that CD47 was a direct downstream target gene of ARID1A in GC. Utilizing univariate and multivariate survival analyses, we found that patients with ARID1AlossCD47high expression had a worse prognosis. Estimation of infiltrating immune cells on TCGA data set showed that a higher infiltration proportion of M2 macrophages and Tregs was found in ARID1A mutated CD47 high expression subgroup. Furthermore, application of multispectral immunofluorescence revealed a higher infiltration proportion of M2 macrophages and Tregs in ARID1AlossCD47high GC tissues. Conclusion: Loss of ARID1A is strongly correlated with high CD47 expression in GC, and combination of ARID1A and CD47 is a promising prognosis factor in GC.

Studying the Role of Chromosomal Instability (CIN) in GI Cancers Using Patient-derived Organoids

Chromosomal instability (CIN) is associated with the initiation and progression of gastrointestinal (GI) tract cancers. Cancers of the GI tract are typically characterized by altered chromosome numbers. While the dynamics of CIN have been extensively characterized in 2D monolayer cell cultures derived from GI tumors, the tumor microenvironment and 3D tumor architecture also contribute to the progression of CIN, which is not captured in 2D cell culture systems. To overcome these limitations, self-organizing cellular structures that retain organ-specific 3D architecture, namely organoids, have been derived from various tissues of the GI tract. Organoids derived from normal tissue and patient tumors serve as a useful paradigm to study the crosstalk between tumor cells in the context of a tissue microenvironment and its impact on chromosomal stability. Such a paradigm, therefore, has a considerable advantage over 2D cell culture systems in drug screening and personalized medicine. Here, we review the importance of patient-derived tumor organoids (PDTOs) as a model to study CIN in cancers of the GI tract.

PARP1 Inhibitor Combined With Oxaliplatin Efficiently Suppresses Oxaliplatin Resistance in Gastric Cancer-Derived Organoids via Homologous Recombination and the Base Excision Repair Pathway

Oxaliplatin (OXA) resistance in the treatment of different types of cancer is an important and complex problem. The culture of tumor organoids derived from gastric cancer can help us to provide a deeper understanding of the underlying mechanisms that lead to OXA resistance. In this study, our purpose was to understand the mechanisms that lead to OXA resistance, and to provide survival benefits to patients with OXA through targeted combination therapies. Using sequence analysis of OXA-resistant and non-OXA-resistant organoids, we found that PARP1 is an important gene that mediates OXA resistance. Through the patients’ follow-up data, it was observed that the expression level of PARP1 was significantly correlated with OXA resistance. This was confirmed by genetic manipulation of PARP1 expression in OXA-resistant organoids used in subcutaneous tumor formation. Results further showed that PARP1 mediated OXA resistance by inhibiting the base excision repair pathway. OXA also inhibited homologous recombination by CDK1 activity and importantly made cancers with normal BRCA1 function sensitive to PARP inhibition. As a result, combination of OXA and Olaparib (PARP-1/2/3 inhibitor), inhibited in vivo and in vitro OXA resistant organoid growth and viability.

Promises and Challenges of Organoid-Guided Precision Medicine

Organoids are self-organizing, expanding 3D cultures derived from stem cells. Using tissue derived from patients, these miniaturized models recapitulate various aspects of patient physiology and disease phenotypes including genetic profiles and drug sensitivities. As such, patient-derived organoid (PDO) platforms provide an unprecedented opportunity for improving preclinical drug discovery, clinical trial validation, and ultimately patient care. This article reviews the evolution and scope of organoid technology, highlights recent encouraging results using PDOs as potential patient "avatars" to predict drug response and outcomes, and discusses critical parameters for widespread clinical adoption. These include improvements in assay speed, reproducibility, standardization, and automation which are necessary to realize the translational potential of PDOs as clinical tools. The multiple entry points where PDOs may contribute valuable insights in drug discovery and lessen the risks associated with clinical trials are also discussed.

Transcriptomic analysis of tumor tissues and organoids reveals the crucial genes regulating the proliferation of lung adenocarcinoma

Background

Accumulative evidence shows that an organoid is a more practical and reliable tool in cancer biology research. This study aimed to identify and validate crucial genes involved in non-small cell lung cancer carcinogenesis and development using the transcriptomic analysis of tumor tissues and organoids.

Methods

Gene set enrichment analysis (GSEA) of tumor tissues, tumor organoids, and normal tissues was performed to reveal the similar and different mechanisms involved in lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) carcinogenesis and progression. Differentially expressed gene analysis, prognostic analysis, and gene co-expression network analysis were further used to identify hub genes involved in LUAD and LUSC carcinogenesis and development. Finally, LUAD cell lines and organoids were used to validate these findings.

Results

GSEA analysis was performed to reveal the similar mechanisms involved in LUAD and LUSC carcinogenesis and development, such as P53 signaling pathway, base mismatch repair, DNA replication, cAMP signaling pathway and PPAR pathway. However, comparing with LUSC organoids, LUAD organoids showed downregulation of immune-related pathways, inflammation-related pathways, MAPK signaling pathways, and Rap1 signaling pathways, although these pathways were downregulated in LUAD and LUSC tissues by comparing with normal lung tissues. Further gene co-expression network analysis and prognostic analysis indicated CDK1, CCNB2, and CDC25A as the hub tumor-promoting genes in LUAD but not in LUSC, which were further validated in other datasets. Using LUAD cell lines and organoid models, CDK1 and CCNB2 knockdown were found to suppress LUAD proliferation. However, CDC25A knockdown did not inhibit LUAD cell line proliferation but could effectively suppress LUAD organoid growth, indicating that an organoid could be used as an effective tool to study cancer biology in LUAD.

Conclusions

The results revealed CDK1, CCNB2, and CDC25A as the hub genes involved in LUAD carcinogenesis and development, which could be used as the potential biomarkers and targets for LUAD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03043-6.

Revealing ARID1A Function in Gastric Cancer from the Bottom Up

In this issue of Cancer Discovery, Lo and colleagues use CRISPR-based genome engineering in primary human gastric organoids to reveal the functional consequences of ARID1A loss in the early stages of gastric cancer. They show that ARID1A disruption is not tolerated in wild-type organoids, but in the context of TP53 loss, leads to WNT suppression, mucinous metaplasia, enhanced tumorigenicity, and selectively toxicity to BIRC5/Survivin inhibition.See related article by Lo et al., p. 1562.