The HCT116 cell line is a tool in cancer research, derived from a human colorectal carcinoma or colon cancer tumor. Scientists use this cell line as a model system to study the biology of colorectal cancer and to test potential treatments. Its widespread use stems from well-documented genetic features that mirror those found in many human tumors. These features allow researchers to investigate how cancers develop, progress, and respond to therapy in a controlled laboratory environment.
Origin and Establishment of the Cell Line
The HCT116 cell line was established from a tumor sample taken from a man diagnosed with colorectal carcinoma. Creating a cell line involves isolating cancer cells from tissue and providing the nutrients and conditions needed for continuous growth in a lab.
Once isolated, the cells are maintained and distributed by major cell repositories like the American Type Culture Collection (ATCC). The involvement of institutions such as the National Cancer Institute (NCI) ensures a standardized and genetically consistent population is available to scientists. This standardization is important for the reproducibility of experimental results across different laboratories.
Distinct Genetic and Molecular Characteristics
A notable feature of HCT116 cells is their near-diploid karyotype, meaning they have 45 chromosomes, which is close to the 46 found in normal human cells. Many cancer cell lines are aneuploid, with chaotic numbers of chromosomes that can complicate genetic studies. The stable chromosome count in HCT116 cells provides a cleaner genetic background, making it easier to attribute experimental outcomes to specific gene functions or drug effects.
A characteristic of the HCT116 line is its deficiency in the DNA Mismatch Repair (MMR) system. The MMR system functions like a biological spell-checker, correcting errors that occur during DNA replication. HCT116 cells have a mutation in the MLH1 gene, a component of this repair machinery. This defect makes the MMR system non-functional, leading to a high rate of mutations in DNA sequences known as microsatellites. This condition, called microsatellite instability (MSI), is a hallmark of certain colorectal cancers, making HCT116 a model for studying these tumors.
These cells also harbor activating mutations in oncogenes that drive cancer growth. They possess a mutation in the KRAS gene, which locks the KRAS protein in a permanently “on” state, promoting cell division. Additionally, HCT116 cells have a mutation in the PIK3CA gene, which activates another pathway that encourages cell proliferation and survival. The presence of these mutations, which are frequently found in patient tumors, makes the cell line relevant for testing drugs that target these signaling pathways.
In contrast to their oncogene mutations, HCT116 cells are wild-type for the p53 tumor suppressor gene. The p53 protein helps protect the genome by halting the cell cycle or initiating cell death in response to DNA damage. Many cancer cell lines have mutated, non-functional p53. The presence of a functional p53 pathway in HCT116 cells allows scientists to investigate how cancer cells with an intact damage-response system behave. Researchers have also engineered HCT116 sub-lines where the p53 gene is knocked out, providing a tool to directly compare the effects of its presence or absence.
Primary Uses in Cancer Research
The genetic profile of HCT116 cells makes them valuable for drug discovery and screening. Pharmaceutical companies and academic labs use these cells to test the effectiveness of new anti-cancer compounds. Their known oncogene mutations make them useful for evaluating targeted therapies designed to inhibit those pathways. Researchers can expose the cells to a drug and measure changes in cell growth or survival to determine its potential as a therapeutic agent.
The cell line’s functional p53 pathway makes it a model for studying apoptosis (programmed cell death) and the cell cycle. Scientists can introduce DNA-damaging agents, like chemotherapy or radiation, and observe how the p53 system responds. This research helps uncover how some cancer cells evade death despite treatment. These studies help develop strategies to make cancer cells more sensitive to therapies that induce apoptosis.
The cell line’s defect in DNA mismatch repair is leveraged to study this cellular vulnerability. Researchers use it to understand the consequences of a failed DNA repair system and to explore therapies that target MSI-high tumors. This is relevant to the development of immunotherapies, as MSI tumors accumulate mutations that can be recognized by the immune system. The cell line provides a platform to test drugs that might enhance this immune recognition.
HCT116 cells are also used to create xenograft tumor models. This process involves injecting the human cancer cells into immunocompromised mice, where they grow into tumors. These models allow researchers to study tumor development, metastasis (the spread of cancer), and treatment response in a living organism. Observing how a drug affects tumor growth in a mouse provides more comprehensive data than cell culture experiments alone.
Laboratory Growth and Maintenance
In the laboratory, HCT116 cells are grown as an adherent monolayer, attaching and spreading out on the surface of a plastic culture flask. Under a microscope, they display an epithelial-like morphology, appearing as irregularly shaped cells that grow in patches.
Cultivation requires specific laboratory conditions. They are cultured in a nutrient broth, such as McCoy’s 5A or DMEM, supplemented with fetal bovine serum to provide growth factors. The flasks are kept in a humidified incubator at 37°C with a 5% carbon dioxide (CO2) atmosphere to maintain the correct pH.
A practical advantage of HCT116 cells is their rapid growth rate, with a population doubling time between 18 and 27 hours. When the cells cover most of the flask surface, they are subcultured, or “split.” This involves detaching them with an enzyme and transferring a fraction to new flasks to continue their growth.