A Novel In Vitro Model of Human Mesothelioma for Studying Tumor Biology and Apoptotic Resistance
Thursday, August 25th, 2005.
American Journal of Respiratory Cell and Molecular Biology. Vol. 33, pp. 541-548, 2005. Published ahead of print on August 25, 2005. [Link]
Ki-Up Kim*, Shannon M. Wilson*, Keith S. Abayasiriwardana, Rodney Collins, Lars Fjellbirkeland, Zhidong Xu, David M. Jablons, Stephen L. Nishimura and V. Courtney Broaddus
Lung Biology Center or Department of Pathology, San Francisco General Hospital, University of California San Francisco; and Cancer Research Institute, UCSF Comprehensive Cancer Center, University of California San Francisco, San Francisco, California
Correspondence and requests for reprints should be addressed to V. Courtney Broaddus, M.D., Lung Biology Center, Box 0854 UCSF, San Francisco, CA 94143-0854. E-mail: cbroaddus@medsfgh.ucsf.edu
Abstract
Like many tumors, malignant mesothelioma exhibits significant chemoresistance and resistance to apoptosis in vivo that is not seen in current in vitro models. To study the mechanisms of this multicellular resistance, biologically relevant in vitro models are necessary. Therefore, we characterized and tested human mesothelioma tissue grown in vitro as tumor fragment spheroids. After 5–10 d in culture, fragments from each of 15 human mesothelioma tumors rounded into spheroids. The tumor fragment spheroids maintained multiple characteristics of the original tumors for up to 3 mo including the presence of viable mesothelioma cells, macrophages, and a collagen- rich stroma. In 14-d-old spheroids, mesothelioma cells showed the same proliferation rate and expression of a death receptor, DR5, as in the original tumor. To determine responses to treatment, we treated tumor fragment spheroids grown from three separate tumors with agents, TNF-related apoptosis-inducing ligand (TRAIL) plus cycloheximide, that induced near total apoptosis in three human mesothelioma cell lines (M28, REN, MS-1) grown as monolayers (94 ± 6% apoptosis; mean ± SEM). Compared with mesothelioma cells in monolayers, mesothelioma cells in the spheroids were resistant to TRAIL plus cycloheximide (32 ± 4% apoptosis; mean ± SEM). Apoptotic resistance of mesothelioma cells was significantly reduced by inhibiting either the PI3K/Akt pathway with LY294002 (47 ± 6% apoptosis) or the mTOR pathway with rapamycin (50 ± 17% apoptosis). We conclude that human mesothelioma can be maintained in vitro in a biologically relevant model that exhibits apoptotic resistance, thereby permitting study of its tumor biology and of novel approaches to therapy.
Key Words: collagen • death receptor DR5 • mTOR • multicellular resistance • PI3K/Akt survival pathway • TNF-related apoptosis-inducing ligand (TRAIL) • tumor-associated macrophage • tumor fragment spheroid
Glossary
- therapy
- any of the measures taken to treat a disease. Unproven therapy is any therapy that has not been scientifically tested and approved. Use of an unproven therapy instead of standard (proven) therapy is called alternative therapy. Some alternative therapies have dangerous or even life-threatening side effects. For others, the main danger is that a patient may lose the opportunity to benefit from standard therapy. Complementary therapy, on the other hand, refers to therapies used in addition to standard therapy. Some complementary therapies may help relieve certain symptoms of cancer, relieve side effects of standard cancer therapy, or improve a patient's sense of well-being. The ACS recommends that patients considering use of any alternative or complementary therapy discuss this with their health care team.
- cell
- the basic unit of which all living things are made. Cells replace themselves by splitting and forming new cells (mitosis). The processes that control the formation of new cells and the death of old cells are disrupted in cancer.
- cancer
- malignancy; a group of diseases typified by abnormal, generally out-of-control, cell growth.
- tissue
- a collection of cells, united to perform a particular function.
- tumor
- an abnormal lump or mass of tissue. Tumors can be benign (not cancerous) or malignant (cancerous).
- mesothelioma
- a tumor derived from mesothelial tissue, such as the peritoneum (lining the abdomen) or pleura (lining the lungs). More on mesothelioma.
- apoptosis
- a type of cell death in which the cell basically commits suicide; scientists believe some types of cancer may originate from an interruption of this programmed cell death, allowing cells to grow out of control.
