COMPARISON OF GROWTH AND DIFFERENTIATION OF NORMAL AND NEOPLASTIC CANINE KERATINOCYTE CULTURES

Neoplastic canine keratinocytes derived from a spontaneous oral squamous cell carcinoma were maintained in culture for more than 45 passages. The presence of desmosomes and keratin filaments was demonstrated by electron microscopy and immunohistochemistry. The keratinocytes were grown in two different culture conditions to induce variations in the stage of differentiation, i.e., in submerged cultures and at the air-liquid interface. For comparison, normal canine keratinocytes were grown under the same conditions. Anisocytosis was present in neoplastic cultures grown submerged in medium. Grown at the air-liquid interface, neoplastic keratinocytes differentiated into a well-organized, multilayered stratified squamous epithelium analogous to normal keratinocytes. Rare areas of irregular growth and formation of whorls were detected. Expression of lectin binding sites and specific cell surface antigens of neoplastic and normal keratinocytes demonstrated marked similarities between the two cell lines. Neoplastic cells lacked certain surface antigens that are present on normal cells. Squamous cell carcinoma cells grew faster than normal canine keratinocytes as demonstrated by growth curve evaluation. Neoplastic keratinocytes responded to growth stimulation by epidermal growth factor and cholera toxin as do normal keratinocytes. Neoplastic cells grown in medium lacking these factors proliferated faster than growth factor stimulated normal keratinocytes.