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By using a protective chamber to shield mouse skin seeded with BCC, researchers say they have created the first reliable means of transplanting these tumors.0
Although researchers can easily transplant cancers - including melanoma, breast cancer and prostate cancer - from humans to animals and animals to animals for scientific study, "We've never been able to do that reliably with BCCs," says Ruby Ghadially, M.D., professor of dermatology at the University of California, San Francisco, and a study co-author.
Previously, efforts to transplant human BCCs into immunodeficient mice yielded little or no growth (Grimwood RE, Tharp MD. J Dermatol Surg Oncol. 1991. 17(8): 661-666).
"We're not 100 percent sure why previous attempts failed," while the new method succeeded, she says.
Explanations could include the high number of BCC cells transplanted, "or it could be because we gave them more of the support they need in terms of normal keratinocytes, a normal dermis and normal subcutaneous tissue."
Using the silicone chamber also allows one to transplant BCCs directly onto the skin's surface, where they are used to growing, instead of injecting them the below the skin, Dr. Ghadially tells Dermatology Times.
Researchers' use of severely immunodeficient (SCID) mice also likely contributed to the new method's success, she says.
Dr. Ghadially and her colleagues began by establishing a mouse BCC line (ASZ001) from a Ptch1+/- mouse that they had exposed to UVB radiation (515 mJ/cm2 ) thrice weekly from age 2 months to 1 year.
They then combined the ASZ001 cells with wild-type mouse epidermal keratinocytes and seeded them into round, 6 mm silicone chambers that had been placed on the fascia of SCID mice and sutured into the surrounding skin.
"The function of the chamber is basically to hold away the host mouse skin while the tumor is developing.
"If we hadn't done that, the skin would probably have grown over the transplanted cells, and the tumor might or might not have taken hold," Dr. Ghadially says.
After transplanting the cells, researchers covered the chambers with Tegaderm (3M) for four to 16 weeks.
Then they harvested BCC tumor cells from the chambers and analyzed them using light microscopy. Preparatory steps here included staining with X-gal, paraffin-embedding and sectioning.
Microscopic analysis showed that, like some human BCCs, the resulting tumors consisted of nests and trabeculae of basaloid cells with focal squamatization, extending into the underlying stroma with an infiltrating growth pattern.
Researchers also observed stromal reaction and fibrosis, she says.
The only surprise the study delivered was that its method worked so predictably, when transplantation of BCC cells hadn't previously been done with any degree of robustness, she says.
"People have occasionally gotten a BCC to grow (in a murine model) from a piece they took from another BCC.
"But now we do this reliably - in fact, we've done it many times. I presume other labs are beginning to use our method.
"And my collaborator Dr. Epstein has begun to do it in his lab with some of his other studies," Dr. Ghadially says.