Journal Article

Targeting mutant RAS in patient-derived colorectal cancer organoids by combinatorial drug screening

Clevers, Hans, Gerwen, Bastiaan van, Bernards, René, Wetering, Marc van de, van der Ven, Marieke, Mertens, Sander, Snippert, Hugo J, Bos, Johannes L, Drost, Jarno, Egan, David A, Verissimo, Carla S, Overmeer, René M, Ponsioen, Bas, Verlaan-Klink, Ingrid

2016

Overview

Colorectal cancer (CRC) organoids can be derived from almost all CRC patients and therefore capture the genetic diversity of this disease. We assembled a panel of CRC organoids carrying either wild-type or mutant RAS, as well as normal organoids and tumor organoids with a CRISPR-introduced oncogenic KRAS mutation. Using this panel, we evaluated RAS pathway inhibitors and drug combinations that are currently in clinical trial for RAS mutant cancers. Presence of mutant RAS correlated strongly with resistance to these targeted therapies. This was observed in tumorigenic as well as in normal organoids. Moreover, dual inhibition of the EGFR-MEK-ERK pathway in RAS mutant organoids induced a transient cell-cycle arrest rather than cell death. In vivo drug response of xenotransplanted RAS mutant organoids confirmed this growth arrest upon pan-HER/MEK combination therapy. Altogether, our studies demonstrate the potential of patient-derived CRC organoid libraries in evaluating inhibitors and drug combinations in a preclinical setting. Recent technical advances mean that miniature replicas of many tissues can be grown in the laboratory. These so-called organoids provide scientists with model systems that are not as limited as simple, two-dimensional sheets of cells growing in a petri dish, and less labor and resource intensive than studies using laboratory animals. In particular, organoids grown from tumor cells from cancer patients have been suggested as having numerous advantages over both laboratory-grown cancer cells and mice when it comes to testing potential new anticancer drugs. Mutations in a gene called KRAS are common in many types of cancer including colon cancer. Tumors with these mutations are difficult to treat and so far virtually all attempts to generate compounds that selectively interfere with the KRAS protein encoded by the mutant gene have failed. Instead, drugs that indirectly inhibit this protein’s effects by targeting other proteins in the same signaling pathway are currently being tested on patients. However, there is still a need for better ways to pre-test whether these drugs will be effective in humans without having to expose the patient to side effects or an ineffective drug. Now, Verissimo, Overmeer, Ponsioen et al. have tested clinically-used KRAS pathway inhibitors and drug combinations against normal colon organoids and colon cancer organoids derived from patients with colon cancer. Gene editing techniques were used to introduce KRAS mutations into some of the normal organoids grown from healthy tissue, and into cancer organoids grown from tumors that had a normal copy of the KRAS gene. In all cases, only those organoids with mutant forms of the KRAS gene were resistant to the treatments. Furthermore, when organoids with the KRAS mutation were treated with some combination therapies that are currently being tested in clinical trials, the tumors stopped growing but the tumor cells failed to die. Similar drug treatments on mice carrying human colon cancer organoids confirmed these results, which is in line with previous studies where tumor tissue from human patients was transplanted into mice. These findings show that collections of tumor organoids from multiple patients could help researchers to quickly identify and optimize targeted anticancer therapies before they are incorporated into clinical trials. In the future, clinical studies are needed to verify how accurately the testing of cancer drugs on organoids predicts whether the drug will or will not work in patients.

• Publisher: eLife Science Publications, Ltd,eLife Sciences Publications Ltd,eLife Sciences Publications, Ltd
• Subject: Antineoplastic Agents - isolation & purification / Antineoplastic Agents - pharmacology / Cancer / Cancer Biology / Care and treatment / Clustered Regularly Interspaced Short Palindromic Repeats / Colorectal cancer / Colorectal Neoplasms - drug therapy / CRISPR / Developmental Biology and Stem Cells / Drug Evaluation, Preclinical - methods / Drug screening / Drug therapy / Drug therapy, Combination / Gene mutations / Genetic aspects / Health aspects / Humans / KRAS / Metabolic pathways / Methods / Mutant Proteins - antagonists & inhibitors / Organoids / Organoids - drug effects / ras Proteins - antagonists & inhibitors / Recombination, Genetic / targeted therapy / Xenografts