Cancer cell and tissue models are adapted for use in a research setting allowing for the direct study of a complex set of diseases. As models improve, their use in research has proven pivotal to better diagnosing, treating and even preventing cancer. Here, we’ll look at the pros and cons of 3 common cancer cell models: cancer cell lines, spheroid 3D cell culture and tumor samples from patients.
Let us know what other cancer cell models you’d like us to write about and which models work for your research needs in the comments below!
2D Cancer Cell Lines
A cancer cell line is a collection of cells capable of dividing and growing in vitro. They have been grown and studied for over 60 years, starting with the now infamous HeLa cell line. Cell lines are extremely popular and have been in use for long enough that they are well-regarded and trusted to produce reproducible insights. There are however some drawbacks as we’ll discuss below.
|Don’t break the bank: Relatively inexpensive to maintain and store cells when compared to animal models.|
|Commonly used: Labs across the globe can each be studying the same cells and so extensive literature is available on the various cells lines.|
|Grow forever: Most cell lines will grow indefinitely when cultured correctly although it is recommended to check for contamination and also genetic/phenotypic drift in longer term samples.|
|Easy peasy: when compared to animal models, cell lines require little in the way of maintenance|
|Storable: Cells can be preserved easily.|
|Wide range of possibilities: Most cell lines have a fast rate of replication increasing the rate at which experiments may be conducted and opening up the range of experiments that are possible.|
|Minimal technical expertise: Since cell lines are selected in part because of their ease to culture, they are not technically difficult to manage or manipulate.|
|Easy to sequence: As the cells are all genetically similar they are very straightforward to sequence as opposed to tissue samples from patients where there are many cell types present. It’s also a lot cheaper to sequence as homologous population of cells.|
|“I got that too!”: Highly reproducible results.|
|Invasion of the mutants: May be open to genetic and phenotypic drift as mutations form and cells that are best adapted to their artificial environment are selected but this is the subject of much debate. Cell lines with genetic modifications may be very different from their parental origin.|
|Knowing your subtype: It isn’t always known from what subtype a cancer cell line has been derived. A lot of cell lines have been around for a lot longer than we’ve known about how important cancer cell types are.|
|Hello HeLa: Open to contamination either by microorganisms or by other cells, most notoriously HeLa cells. The latter case is called a “false” cell line but can be minimized by carefully characterizing cell lines before meaningful research takes place.|
|No sharesies: Because of how cheap these cells are to buy and how quickly they can be grown, it is common for labs to swap or gift cells lines to other labs. This has the dual problem of both spreading any contaminants and of assuming that cell lines have already been well-characterized. A potential solution would be for journals to require proof of cell line characterization before accepting a paper for publication, however this has its own drawbacks too.|
|Primary problem: Some cancer cell lines were not developed from primary tumors but instead from metastases. Thus, there are inherent variabilities in each tumor sample.|
|Trouble translating: Cell-cell and cell-matrix interactions seen in vivo are lost in vitro making these cells less clinically relevant and less useful in translational research.|
|“Where am I from?”: Very little is known about the origin of some cell lines as the importance of cancer subtypes was not known until more recently and many of the cell lines are very old. This has caused the National Cancer Institute (NCI) to retire the NCI-60, its panel of 60 human cancer cell lines grown in culture, from its drug-screening programme after 25 years of use.|
3D Spheroid Cell Models:
3D culturing cancer models are cell cultures that are grown to promote a three-dimensional structure allowing you to recreate tumor-like growths far more similar to in vivo tumors than monolayer cultures. They allow researchers to characterize tumor progression and perform drug screening using non-animal models. As preclinical models, they more closely resemble the original cancer than 2D cultures and are thus often more relevant in translational research.
|Testing, testing, 1, 2: Excellent model of drug resistance and sensitization as they mirror the penetration barrier issue and the lower growth fraction of tumor cells in clinical models.|
|Testing, testing, 3, 4: Can more accurately screen antineoplastic agents and radiation due to the presence of strengthening cell-cell interactions and the chemo- and radio-therapy resistant hypoxic, necrotic core characteristic of tumor growth in vivo|
|Something unique: Allows tumor cells to develop more heterogeneity as different cells are exposed to non-uniform distributions of oxygen and nutrients, chemical factors, and cell-cell and cell-matrix interactions. This creates a more clinically relevant tumor microenvironment. Also these cell-cell interactions are thought to be crucial for cancer metastasis, invasion and anchorage-dependent growth.|
|Death by light: Useful in the development and testing of anticancer photodynamic therapy regimens.|
|Easy peasy: Less labor intensive than animal models. Easily adapted for medium-to-high throughput applications.|
|Don’t break the bank: Inexpensive when compared to animal models.|
|“I got that too!”: Highly reproducible results.|
|Not too big, not too small: It can be challenging to develop and maintain spheroids of uniform size, however it can be done.|
|Insufficient funds: Forming spheroids from a small seed number of cells can be very challenging. It you only have a small number of cells with which to work, it may not be possible to form a stable culture.|
|Keeping it simple: Limitations on how complex you can make the spheroids in a reliable, sustainable and reproducible manner as each spheroid will have different ratios of cells types|
|Assay Issues: There is a lack of reliable, simple, standardized assays of cellular responses in situ, prediction of in vivo activity, as well as poor integration with high throughput systems. Hopefully, this problem will, over time, become less of an issue as more research is done.|
Tumor Samples from Patients
The vision of the healthcare system is personalized medicine where each patient receives a treatment regime that is exactly designed for their individual case and has already proven effective in a cancer model specific for their cancer subtype and stage. Therefore, extracting tumor samples from patients in order to test various treatments without risk to the patient sounds very appealing. The same is true for extracting tumor cells in so-called “liquid” (or blood) cancers. Tumor samples are also very helpful for translational research.
Tumor samples are collected in a clinical setting and whatever remains after pathologic diagnosis is stored, for example by snap freezing in liquid nitrogen or preserved in a fixative, such as RNAlater (for RNA extraction) or FFPE (formalin fixed paraffin embedded to preserve tissue architecture, for histological analysis).
Many tumor banks collect their tumor samples from tissue samples not needed for pathologic diagnosis, after patients undergo surgery to remove the tumor.
|Chemo: Tumor’s resistance to chemotherapy can be assessed. This is useful when deciding how to treat patients and also in characterizing cancer subtypes as generally resistant or not and to study resistance factors.|
|Expand cell lines: Primary cell lines can be developed for basic and translational research using tumor tissue.|
|Storage: Fresh tumors can be snap frozen in liquid nitrogen or preserved in a fixative, such as RNAlater (for RNA extraction) or FFPE (formalin fixed paraffin embedded to preserve tissue architecture, for histological analysis)|
|Aunty Jen: Cancer cell antigens can be studied in translational medicine with the hope of developing new therapies, such as allogeneic antibodies and antigen-primed dendritic cell.|
|“I know you!”: Some common cancer cell lines may not be as similar to their original cancer in terms of their genetic profile as desired but this issue is minimized when using fresh tumor cell samples.|
|Comparing jeans: Tumor cell gene expression can be analyzed by DNA and RNA extraction which allows for examination of the genetic basis of various cancers types|
|Gimme, gimme, gimme: In some countries any tissue taken from a patient during surgery not needed by their case pathologist is considered medical waste and so tissue samples are straightforward to come by. Alternatively, the samples can be obtained by informed consent from the patient.|
|Costly: More expensive than cancer cell lines or spheroids.|
|Newbie: Newer and so less proven and well-established an approach. There is less literature available and since every tumor is different, you’re not working with a standardized set of cells but a complex, unique tissue.|
|Not as prolific: Cells eventually go into cellular senescence and may have a slow doubling time making them more challenging to work with. By immortalizing the cells, you’re going to have to deal with the problem of genetic drift.|
|Teeny weeny: As tumors are now found earlier and earlier in their growth, they tend to be smaller and so there is may a shortage of samples. This is becoming less of a problem with the establishment of so many commercial tumor tissue banks.|
|“No, thank you”: In countries where patient consent for samples to be used must be acquired, there may be a reduction in how simple it is to obtain tissue samples creating a shortage.|
|Not the tumor you used to be: Genetic variance from the original tumor after prolonged growth in vitro may occur.|
There are many upsides and downsides to the various cancer models available. Often, the best model is dependent on the individual needs of the researcher. While cell lines and spheroids lend themselves very well to basic research, tumor samples from patients are ideal for translational research.
Have you tried any of these cancel models? Let us know in the comments below!