Spontaneously Regressing Malignant Melanomas

There is a strain of Sinclair miniature swine that develops an aggressive form of melanoma very similar to those found in humans. This aggressive melanoma has the unique attribute of spontaneously regressing after going through a complete metastatic phase.

Sinclair miniature swine display cutaneous melanoma lesions at birth or develop lesions shortly thereafter. They have been found to develop an immune response to the melanoma, then the lesions regress. The vast majority of animals subsequently remain free of tumors.

Sinclair miniature swine melanoma has many features in common with human malignant melanomas: tumors develop spontaneously, swine possess a wide spectrum of benign melanocytic lesions capable of malignant transformation, melanomas in pigs histopathologically resemble human superficial spreading melanoma, metastatic disease is correlated with deeply invasive cutaneous tumors, the pattern of metastatic spread is analogous to the distribution of metastases in human melanoma, the histopathology of cutaneous regression is similar, a tumor-related immune response occurs in the host, and a genetic component is readily apparent that is comparable to the genetic component of some melanomas in humans.

The Sinclair miniature swine melanoma model provides a unique opportunity to investigate host-tumor-cell interactions in a clinically relevant system. This gives scientists a rare opportunity to study development, regression, and therapeutic compounds in a spontaneously occurring malignant cancer. The Sinclair miniature swine melanoma model also provides an excellent system in which to investigate the progressive cellular changes during the transition from normal through pre-malignant to malignant and to metastatic melanoma, as well as the cellular changes that occur during the spontaneous regression of melanoma lesions.

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