Postconfluency MDCK monolayers as an in vitro model of solid tumor chemosensitivity

Multilayered Cultures of NSCLC cells grown at the Air-Liquid Interface allow the efficacy testing of inhaled anti-cancer drugs

Evidence supports the advantages of inhalation over other drug-administration routes in the treatment of lung diseases, including cancer. Although data obtained from animal models and conventional in vitro cultures are informative, testing the efficacy of inhaled chemotherapeutic agents requires human-relevant preclinical tools. Such tools are currently unavailable. Here, we developed and characterized in vitro models for the efficacy testing of inhaled chemotherapeutic agents against non-small-cell lung cancer (NSCLC). These models recapitulated key elements of both the lung epithelium and the tumour tissue, namely the direct contact with the gas phase and the three-dimensional (3D) architecture. Our in vitro models were formed by growing, for the first time, human adenocarcinoma (A549) cells as multilayered mono-cultures at the Air-Liquid Interface (ALI). The in vitro models were tested for their response to four benchmarking chemotherapeutics, currently in use in clinics, demonstrating an increased resistance to these drugs as compared to sub-confluent monolayered 2D cell cultures. Chemoresistance was comparable to that detected in 3D hypoxic tumour spheroids. Being cultured in ALI conditions, the multilayered monocultures demonstrated to be compatible with testing drugs administered as a liquid aerosol by a clinical nebulizer, offering an advantage over 3D tumour spheroids. In conclusion, we demonstrated that our in vitro models provide new human-relevant tools allowing for the efficacy screening of inhaled anti-cancer drugs.

Evidence that hepatocyte growth factor abrogates contact inhibition of mitosis in Madin-Darby canine kidney cell monolayers

It is becoming increasingly apparent that hepatocyte growth factor (HGF) plays an important role in kidney development, regeneration, and transformation to carcinoma. Previous in vitro studies have shown that HGF stimulates cell scattering, but not proliferation, in the renal epithelial cell line Madin-Darby canine kidney (MDCK) when grown on plastic at low density. This communication demonstrates that HGF treatment of confluent monolayers of MDCK also stimulates DNA synthesis and cell division. HGF stimulated thymidine incorporation in confluent MDCK cell monolayers grown on plastic in a dose dependent fashion, but did not stimulate thymidine incorporation in MDCK cells at 10-20% confluency on plastic. Additionally, basolaterally, but not apically, applied HGF stimulated thymidine incorporation in confluent MDCK cell monolayers grown on filters. Immunofluorescent labeling of nuclei in control and HGF treated MDCK cell monolayers grown on filters demonstrated an increase in mitotic figures. Confocal X-Z section views and direct cell counts of MDCK cell monolayers grown on filters demonstrated an increase in cell number after HGF treatment compared to controls. This is the first report of HGF stimulating cell proliferation in previously quiescent renal epithelial cell monolayers. This model will be useful for studying the mechanisms controlling cell proliferation rates in epithelial tissue.

Cytotoxic effects of anticancer agents on subconfluent and multilayered postconfluent cultures

The cytotoxic effects of conventional (doxorubicin, 5-fluorouracil, cisplatin) and investigational (2',2'-difluorodeoxycytidine, hexadecylphosphocholine, EO9, rhizoxin) anticancer drugs were studied in subconfluent and multilayered postconfluent cultures of human colon and ovarian carcinoma cell lines. Chemosensitivity was assessed 4 days after a 24-h drug exposure with the sulphorhodamine B assay. Except for rhizoxin, all drugs tested yielded an EC50 (drug concentration producing absorbance readings 50% lower than those of non-treated wells) in postconfluent cultures that were higher than an EC50 obtained with subconfluent cultures. Compared with subconfluent cultures, postconfluent cultures showed decreased cellular nucleotide concentrations and ATP/ADP ratios, in addition to an increased percentage of G0/G1 cells. The activity of DT-diaphorase, a reductase involved in the bioactivation of EO9, was similar in sub- and postconfluent cultures. These results indicate similarity of the postconfluent model presented with those obtained with in vivo models and more complex in vitro techniques.

Growth, morphology and chemosensitivity studies on postconfluent cells cultured in 'V'-bottomed microtiter plates

This study assessed the growth pattern, cellular organisation and chemosensitivity of established human tumour cell lines growing as postconfluent cultures in 'V'-bottomed, 96-well microtiter plates. Cross-sections of the colon (HT29, SW620, SW1116), ovarian (A2780) and head and neck (UM-SCC-22B) carcinoma microcultures allowed in situ evaluation of the cellular organisation in the wells. After 5 days of growth, every cell line had reached confluence, but each of them displayed a specific pattern of cell stacking which ranged from two to ten layers. Postconfluent HT29 cells displayed morphologic features suggestive of some degree of enterocytic differentiation. Growth and cytotoxicity could be studied reliably and reproducibly in this system with the sulforhodamine B protein assay. Against HT29 postconfluent cultures, the EC50's (drug concentrations producing absorbance readings 50% lower than those of non-treated wells) of 5-fluorouracil and of the ether lipid, hexadecylphosphocholine, were 1 mM and 50 microM respectively. The possibility to perform chemosensitivity tests using semiautomated microtiter plate technology supports further evaluation of this system as an alternative antitumour drug testing model.

Standardized kinetic microassay to quantify differential chemosensitivity on the basis of proliferative activity

Conventionally in vitro cytotoxicity assays are performed as single-end-point determinations. To compensate for the diversity of growth rates among different cell lines in this report we describe a computerized kinetic chemosensitivity assay based on quantification of biomass by staining cells with crystal violet. As a prerequisite four human breast cancer cell lines (MDA-MB-231, MCF-7, T-47-D and ZR-75-1) were characterized with regard to oestrogen and progesterone receptor content, modal chromosome number and proliferation kinetics depending on the number of passages in culture. With prolonged time in culture for ZR-75-1 exposed to various concentrations of cisplatinum a dose-related increase in drug effect was observed. Owing to a correction of the T/C values for the initial cell mass (at the time when drug is added) a sharp distinction between cytostatic and cytocidal drug effects becomes obvious in plots of corrected T/C values versus time of incubation. The influence of the untreated control on the corrected T/C values and possible time courses of theoretical inhibition profiles (reflecting cytostatic, transient cytotoxic or cytocidal drug effects as well as development of resistance) and their relationship to the corresponding growth curves of drug-treated cells are discussed. Chemosensitivity assays with diethylstilbestrol dipropionate, tamoxifen, melphalan, cisplatinum, vinblastine, Adriamycin and 5-fluorouracil prove the theoretical considerations to be true for MDA-MB-231, MCF-7, T-47-D and ZR-75-1 human breast cancer cell lines in practice.

The regulation of sterol metabolism by cell interactions

Total and free cholesterol levels in C6 glial cells are regulated by a cell interaction-dependent mechanism that operates independently of exogenous cholesterol and serum lipoproteins. This mechanism, which is activated by changes in culture density, coordinately regulates the activities of HMG-CoA reductase and acyl-CoA:cholesterol acyltransferase (ACAT). Both enzyme activities are low in sparse density cultures, rise as density increases from sparse to moderate, and decrease with further density increases. When culture density is abruptly elevated, both enzyme activities decay rapidly and with biphasic kinetics. Neither enzyme phosphorylation nor diffusible cytosolic factors appear to be directly involved in density suppression of HMG-CoA reductase. Studies with human fibroblasts that are defective in LDL receptor function demonstrate that density regulation does not require a functional LDL receptor. Extracellular matrix and soluble factors have also been ruled out as intercellular mediators. The specific growth rate of C6 cultures changes with density in the same manner as sterol metabolism. The possibility that growth and sterol metabolism are regulated by a common cell interaction-dependent mechanism is discussed.