Finally We Are Growing Skin Cancer on Rats
Research Update From the Olasz-Lazarova Lab
Two years ago we proposed in a grant to establish an orthotopic squamous cell carcinoma (SCC) model in rats to study cancer biology and therapeutics. Why did we choose this model and why rats? The scarcity of animal models that mimic this type of skin cancer has slowed the development of new therapeutic agents. Animal models of cutaneous SCC fall into three major categories – genetic, ultraviolet light or chemical-induced carcinogenesis, and xenograft models. In simple terms, genetic models rely on modification of oncogenic pathways and can be excellent tools for development of targeted therapies. Unfortunately, both UV and chemical-induced carcinogenesis take many weeks and mainly result in papilloma rather than SCC formation. In an orthotopic xenograft model, a graft from one species, which in our case is human SCC tissue or human SCC cell line, is transplanted onto the appropriate site, i.e. skin. Promising examples of orthotopic xenograft transplant models have been published in head and neck SCC literature. In a previous study by our colleagues and friends at the NIH Dermatology Branch, intradermal injection of murine SCC cell suspension resulted in 100% engraftment of tumor in hairless mice. Therefore, we had high hopes to establish a similar model in rats. Why rats? First they are larger animals than mice, thus providing more tissue. Second, they allow the possibility to use multiple procedures already established in our lab. Importantly, we also have extensive preliminary data on the effect of ionizing radiation on normal rat skin, thus allowing us to test treatment modalities of SCC with radiation therapy. Another advantage of this project was a close collaboration with a fellow Dermatology faculty member, Dr. Jozef Lazar, whose expertise in molecular genetics will help us to design genetically modified knock-out rat models.
The main goals of this project were to study tumor behavior depending on primary tumor characteristics and immune status of the donor and to study current and future potential drug therapies. For example, certain immunosuppressive agents have been shown to be radiosensitizers. The use of these agents in combination with radiation could be tested in our novel xenograft animal model. With the advent of personalized medicine, establishment of rat colonies with xenografts originating from an individual patient would enable us to test multiple drugs for their efficacy and resistance.
With this novel approach, superb lab environment, and grant funding through the Froedtert Hospital Foundation, our team (Edit Olasz, MD, PhD; Zelmira Lazarova, MD; Nathan Duncan, and Ashley Schock) worked tirelessly to advance the project. We had several limiting factors, but probably one of the most difficult was to obtain sufficient amount of tissue. According to our IRB protocol, donors needed to have a blood draw to check for certain infections. So we had tissue but no blood, we had blood but not the tissue and so on.
Anybody who has been seriously engaged in scientific work of any kind realizes that over the entrance to the gates of the temple of science are written the words: Ye must have faith. It is a quality which the scientist cannot dispense with.
— Max Planck Where is Science Going?, translated by James Vincent Murphy (1932).
So we had faith, although fading. The few SCC tissues we implanted were not growing. Then we modified techniques, creating a microenvironment conducive for SCC growth using fibroblasts and matrigel glass disks for two weeks before implantation. Then we put our faith into an SCC cell line to get our results. Finally time, effort and faith paid off – our rats developed SCCs which faithfully resemble human tumors and even metastasize into the lungs!
SCC Tumor Formation on Nude Rat
In addition, we found that the SCCs utilize an adhesion molecule called laminin 332 to promote tumor invasion. (Interestingly, Dr. Lazarova was the first to characterize laminin 332 as a pathogenic autoantigen in mucous membrane pemphigoid.)
Most importantly, we were able to identify a microRNA regulatory pathway which is capable of modifying expression of L332. Logically, our next question will be, whether we could influence SCC cancer invasion and metastasis using this particular pathway with targeted therapy.
We are currently growing primary SCC cells derived from a patient and working hard to characterize our model. We have plans to study the interaction of certain immunosuppressive drugs and radiation therapy as well as targeted therapies to block invasion and metastasis.
Stay tuned! We thank you all for your support.