Of all the skin cancer types, melanoma is the most serious form of skin cancer and while accounting for only about 1% of skin cancer cases, it is associated with the highest mortality1. Melanoma begins in melanocytes of the skin's epidermis, but once it becomes invasive into the skin or other parts of the body, it is more difficult to treat and can be fatal. The American Cancer Society's estimates for melanoma in the United States for 2021 are about 106,110 new melanomas to be diagnosed (about 62,260 in men and 43,850 in women) and about 7,180 people are expected to die of melanoma (about 4,600 men and 2,580 women). Fortunately, melanoma is curable, when detected and treated early, with a 98 percent estimated five-year survival rate for U.S. patients2.
In the preclinical setting, the most commonly used syngeneic tumor model is the B16 melanoma. As previously described, the B16-F10 model is highly refractory to most immunomodulators and moderately responsive to focal radiation. We now have characterized the Cloudman S91 syngeneic tumor model, described here, as an additional melanoma model for preclinical oncology studies. In the examples shown below, animal care and use was conducted according to animal welfare regulations in an AAALAC-accredited facility with IACUC protocol review and approval.
Cloudman S91, also called Clone M-3 or S91, is a melanocyte-derived epithelial mouse melanoma cell line from a male DBA/2 mouse. Clone M-3, a melanin-producing cell line, was adapted to cell culture3 from a Cloudman S91 melanoma in a (C X DBA) F1 male mouse obtained from the Jackson Memorial Laboratory, Bar Harbor, Maine. In vitro, Cloudman S91 cells grow as an adherent population taking on an epithelial morphology. In vivo, intradermal implant of these cells in DBA/2J mice results in delayed growth compared to subcutaneous implant. Subcutaneous tumor cells implant in the high axilla with an initial inoculum of 1.0E+06 cells show efficient growth kinetics with a mean doubling time of approximately four days (Figure 1). Animals stay on study for about 20-25 days before they reach euthanasia criteria of excessive tumor burden.