A predictive test for the selection of cancer chemotherapeutic agents for the treatment of human cancer

Pancreatic Cancer Organoids in the Field of Precision Medicine: A Review of Literature and Experience on Drug Sensitivity Testing with Multiple Readouts and Synergy Scoring

Simple Summary

New treatments are urgently needed for pancreatic ductal adenocarcinoma because it is one of the most aggressive and lethal cancers, detected too late and resistant to conventional chemotherapy. Tumors in most patients feature a similar set of core mutations but so far it has not been possible to design a one-fits-all treatment strategy. Instead, efforts are underway to personalize the therapies. To find the treatments that might work the best for each patient, entirely new experimental platforms based on living miniature tumors, organoids, have been developed. We review here the latest international findings in designing personalized treatments pancreatic cancer patients using organoids as testing beds. Our own work adds important clues about how such testing could, and perhaps should, be conducted.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a silent killer, often diagnosed late. However, it is also dishearteningly resistant to nearly all forms of treatment. New therapies are urgently needed, and with the advent of organoid culture for pancreatic cancer, an increasing number of innovative approaches are being tested. Organoids can be derived within a short enough time window to allow testing of several anticancer agents, which opens up the possibility for functional precision medicine for pancreatic cancer. At the same time, organoid model systems are being refined to better mimic the cancer, for example, by incorporation of components of the tumor microenvironment. We review some of the latest developments in pancreatic cancer organoid research and in novel treatment design. We also summarize our own current experiences with pancreatic cancer organoid drug sensitivity and resistance testing (DSRT) in 14 organoids from 11 PDAC patients. Our data show that it may be necessary to include a cell death read-out in ex vivo DSRT assays, as metabolic viability quantitation does not capture actual organoid killing. We also successfully adapted the organoid platform for drug combination synergy discovery. Lastly, live organoid culture 3D confocal microscopy can help identify individual surviving tumor cells escaping cell death even during harsh combination treatments. Taken together, the organoid technology allows the development of novel precision medicine approaches for PDAC, which paves the way for clinical trials and much needed new treatment options for pancreatic cancer patients.

A newly developed in vitro chemosensitivity test (nuclear damage assay): application to ovarian cancer

With a newly developed in vitro chemosensitivity test based on the morphological changes of nuclear damage (nuclear damage assay) described here, we were able to screen currently available anticancer drugs within 24 hr with a 100% success rate. In preclinical chemotherapy using four human ovarian epithelial tumor cell lines and their xenografts in nude mice, the in vitro/in vivo response (sensitive/sensitive and resistant/resistant) rate was 94%. The nuclear damage assay was used to determine the chemosensitivity in 49 patients (60 assays) with ovarian cancer. The response rate of the 13 patients with measurable tumors, 9 of whom showed resistance to CAP (cyclophosphamide, adriamycin, and cisplatin) therapy, was 46% when the patients were given various combination chemotherapy protocols consisting of more than one active agent selected from group A and B agents by the nuclear damage assay. The newly developed in vitro chemosensitivity test proved to be useful when selecting a second-line combination chemotherapy for patients with CAP-resistant ovarian cancer.

Augmentation of Hydroxyurea Cytotoxicity by Sintamil in Human Chronic Myeloid Leukemia Cells

The in vitro effect of sintamil, as a modulator alone and in combination with hydroxyurea (HU), on cytotoxicity was studied in 16 cases of human chronic myeloid leukemia (CML). We investigated the cytotoxicity of the drugs as a function of the exposure dose (HU, 10−4 M; sintamil, 10 μg/ml) and the exposure time (1 h) to the agent. Cytotoxicity was evaluated as the inhibition of incorporation of [3H-methyl]thymidine in the nucleic acids of CML cells. Cytotoxicity of HU was greatly enhanced (P < 0.001) by 1 h exposure of the CML cells to sintamil. The present data indicate that sintamil potentiates the cytotoxic activity of HU in CML cells.

Ex vivo hemodialysis culture system for assessing the activity of cancer chemotherapeutic agents

An ex vivo culture system was developed for assessing the activity of cancer chemotherapeutic agents against tumor cells. The system utilizes artificial capillary culture units and the technique of hemodialysis to expose tumor cells to a chemotherapeutic drug and its metabolites following injection of the drug into an experimental animal. This ex vivo culture system was used to test the activity of 5-fluorouracil (5-FU) against four human colorectal adenocarcinoma cell lines (SW 403, SW 480, SW 620, and SW 707). Cell killing by 5-FU or its metabolites in blood dialysate following intravenous injection was measured by determining colony formation of cells attached to plastic and suspended in 0.3% agar after short-term exposures of 1 to 2 h. The technique was shown to discriminate between the sensitivities of these cell lines and the respective sensitivities to the drug were reproducible. Kinetics of drug clearance from the host animal's blood were shown to be similar to that in humans. The results suggest the system may be useful for testing diverse drugs, including those requiring metabolic activation, against a variety of types of tumor cells.

In vitro short-term test to determine the resistance of human tumors to chemotherapy: Group for Sensitivity Testing of Tumors (KSST)

In a cooperative study conducted by nine different hospitals between 1975 and 1979, the results of a short-term test in vitro (cell suspension, incubation with cytostatics for three hours, determination of the effect of the cytostatic by means of radioactive precursors and liquid scintillation counter) were compared with the results of a cytostatic treatment in 155 patients. Seventy-two patients with ovarian carcinomas, 24 patients with bronchial carcinomas and 18 patients with mammary carcinomas were treated according to a uniform therapy schedule. The remaining patients were treated according to different therapy schedules. The results of the tests in vitro, in which the proliferation-dependent effect of 4-hydroperoxycyclophosphamide and doxorubicin hydrochloride was determined agree well with those of the clinical therapy. Tumors that responded only slightly to cytostatics in the test were also clinically progressive. Of the 76 tumors which proved to be resistant to doxorubicin (concentration 10(-1)mg/ml), 56 (73%) were clinically progressive, 2 tumors (2%) were in remission and 19 (25%) were unchanged. When the alternative evaluations (progression, remission) alone were compared with the test results, 56 (98%) of 57 tumors resistant in the test also proved to be clinically progressive.

Role of laboratory chemosensitivity testing in the selection of cancer chemotherapy for individual patients

Recently several assays have been developed which allow the growth of colonies from cell suspensions prepared from human tumour biopsy specimens. It has been suggested that such assays will provide a reliable means of measuring the chemosensitivity of human tumours for predicting the response to treatment in patients. We have briefly reviewed the previous, largely unsuccessful, attempts at chemosensitivity testing and the potential place of the new assays. The measurement of the survival of clonogenic tumour cells after cytotoxic treatment probably reflects to some extent the survival of cells which in vivo are capable of proliferating to repopulate and regrow the tumour. This endpoint therefore has advantages over alternatives that do not directly measure reproductive cell death, and the assays also have the advantage of suppressing the growth of many non-malignant cells found in tumours. However, technical problems such as the preparation of cell suspensions and the artificial nature of the drug exposure phase of the assays have not been completely overcome and the plating efficiencies remain low in most systems. Work with model systems such as human tumour xenografts tends to support the usefulness of the assays but also highlights some difficulties. Clinical studies of chemosensitivity testing are in progress and initial results are encouraging but inconclusive.

In vitro chemotherapeutic testing of urologic tumors

We studied 20 transitional cell tumors of the bladder and 25 adenocarcinomas of the kidney in vitro to determine their chemotherapeutic sensitivity. The different sensitivity patterns among the individual tumors were demonstrated. Identical drug sensitivity patterns could be identified in the primary and metastatic sites, and in tumor tissue removed from the primary and metastatic deposits in the same patient. Human renal adenocarcinoma maintained in the athymic mouse demonstrated identical chemotherapeutic sensitivity patterns in vitro and in vivo. Our data would support that these in vitro chemotherapy studies may assist in the selection of agents to use in human tumor-bearing hosts.

Screening of toxic compounds in tissue culture

To screen toxicity of chemicals most often easily manageable cultures of less differentiated cells have been used. This work includes 3 fields: (i) Screening of chemicals and fermentation broths for their cytoinhibitory effect, to predict antineoplastic activity. A related practical approach is to achieve optimal antitumour drug therapy by testing drugs on cultures of tumour cells from the patient. (ii) Screening of metal and plastic materials used in medicine, surgery and dentistry for their cytoinhibitory effect to predict local irritation. (iii) Screening of the mutagenicity or transformation capacity of chemicals in tissue culture, to predict their carcinogenicity. In addition, organ-specific cultures of most specialized cells (hepatocytes, ova, nerve cells, heart cells, skin cells, respiratory mucosa, and macrophages) have also been used to predict drug action on corresponding targets in the body. The author's group has focused on 2 new uses of standard cells for screening chemical toxicity: (i) Comparisons of in vitro cytotoxicity with in vivo toxicity of 85 randomly selected drugs indicated that for most drugs a systemic lethal action was brought about by cytotoxicity. A screening model is advocated by which results of cytotoxicity tests are compared with systemic toxicity in vivo to evaluate the systemic cytotoxicity of chemicals. (ii) Combinations of compounds with a cytotoxic lethal action in man indicated by the previous method have been screened in vitro for their combined systemic toxicity. By systematic comparison of results from standardized in vitro tests with in vivo toxicity, steps have been taken to resolve the question of the relevance of screening in tissue culture and to contribute to the development of an emerging subdiscipline to toxicology -- in vitro cytotoxicology.