Four Tumor Models Vital in Our Search for a Cancer Cure
Many early steps in cancer research began in either animal or tumor models. Without these prototypes, researchers would not have been able to create effective drug treatments or find a cure. In the 1960s, the earliest in vivo tumor models were developed, which were ascites models or murine leukemia models.
A paper published in the Molecular Cancer Therapeutics journal discusses the large variety of tumor models that are used in preclinical studies. Over the last 50 years, tumor models have advanced to include syngeneic mouse tumors, models of disseminated disease, and human tumor xenografts. Some are grown in orthotopic locations while others are viewed with the use of various technologies. Each of these tumor models offers both advantages and disadvantages to researchers looking to develop cancer drugs.
Howard Skipper and his team from the Kettering-Meyer Laboratory in Birmingham, Alabama created the first guidelines for ensuring the quality of tumor model development. This group went on to develop two models: the murine L1210 leukemia and the murine P388 leukemia. These models were used to study the rate of leukemic cell growth, anatomic distribution, and how chemotherapy treated mouse tumors.
1. Solid Tumor Models
Over time, solid tumor models were designed and allowed certain parameters to be studied, such as the delay of tumor growth and tumor control. With these cancer models, drugs needed to be given at a dosage that produced normal tissue toxicity. This allows the tumor and its response to be studied for over an extended period.
2. Human Tumor Xenografts
The creation of human tumor xenografts models using immunodeficient mice was a major advancement in tumor model design. There are multiple advantages to using human tumor xenografts when testing cancer drugs including: (1) the malignant cells are human, (2) the models are reproducible, (3) the hosts are easy to gather, (4) there is a significant variety of tumor lines for study, and (5) there is a powerful baseline for drug response statistics.
There are a few disadvantages as well. Human tumor xenografts are costlier models to use, the hosts are immunodeficient, and therefore lack normal immune responses, many of the tumor lines were first created using older, inferior technology, and the tumors are typically grown in an unnatural location.
3. Labeled Tumor Models
In order to study metastatic cancer, researchers developed “labeled” tumor models, which are tumor lines that are tagged with either a green fluorescence protein (GFP), a red fluorescence protein (RFP), or a firefly luciferase. There are multiple benefits to these tumor models such as the ability to study metastasis directly, by following the tumor response with imaging technology, combined with the variety of human cell lines available.
4. Transgenic Tumor Models
Transgenic tumor models have been developed to study cancer in genetically engineered hosts. One benefit of the transgenic models is that the tumor arises naturally in the host, which allows it to be tested over a longer period of time.
Along with these tumor models, other organisms such as yeast have added greatly to the general knowledge of cancer development and metastasis. With the help of a variety of cancer models, scientists are developing more effective treatments and cures.
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Categories: Oncology