Induction of cell death by hydrophobic hydrocarbons.

We present a novel and simple method for inducing cell death. Cells placed in contact with paraffin or other hydrophobic-hydrocarbon substances die. Cell death can be the result of apoptosis, which is also known as programmed cell death (PCD). In apoptosis, cells shrink and undergo both disintegration of the nucleoli and nuclear fragmentation (2). In necrosis, cells swell and disintegrate. Apoptosis is a critical homeostatic mechanism in the body to maintain the necessary proportion of cell proliferation and cell death (10). It is a form of cell suicide. The apoptotic pathway was first elucidated in the Caenorhabditis elegans nematode. A number of critical genes (5) and enzymes, notably the caspases (3), are operative and important to the apoptotic process. PCD can be induced by a variety of physical and chemical means (1). We offer yet another method that is both simple and nontoxic. Paraffin, long used in association with dead cells as a tissue-embedding agent, ironically can be used as a method for inducing cell death. Our experimental protocol consisted of four phases. First, we prepared 1.5–2.0 cc of liquid paraffin (Tissue Prep 2; Fisher Scientific, Pittsburgh, PA, USA) dispensed into polystyrene 6-well tissue culture plates (Falcon Model 3046; Becton Dickinson Labware, Bedford, MA, USA). The paraffin, when cool, formed uniform solid smooth surfaces at the bottom of the wells. Cell controls consisted of plain wells not coated with paraffin and treated identically. The following four cell lines were used: (i) human fetal lung (MRC-5, Catalog No. CCL-171; ATCC, Rockville, MD, USA), (ii) human lung carcinoma (A549, Catalog No. CCL-185; ATCC), (iii) human rhabdomyosarcoma (RD, Catalog No. CCL-136; ATCC) and (iv) human breast carcinoma (MCF 7, Catalog No. HTB-22; ATCC). Confluent monolayers from 75-cm2 tissue culture flasks