Figure 6

A Strong focal expression of mouse S100A7/psoriasin RNA in mammary gland tumors compared to little expression in matched normal mammary gland tissue using in situ hybridization Sections from formalin fixed paraffin-embedded mammary tissue samples matched to the frozen tissue from which RNA was previously isolated for RT-PCR analysis were used for in situ hybridization analysis of mouse S100A7/psoriasin expression: A, C, D, F show hybridization with mouse S100A7/psoriasin ³⁵S-labeled antisense cRNA; B, E show hybridization with mouse S100A7/psoriasin ³⁵S-labeled sense cRNA. A = high magnification (400X) section of normal mammary gland, hybridized with mouse S100A7/psoriasin ³⁵S-labeled antisense cRNA. B = high magnification (400X) adjacent section to A hybridized with mouse S100A7/psoriasin ³⁵S-labeled sense cRNA. C = low magnification (100X) of section from the matched DMBA mammary tumor from same animal shown in A hybridized with mouse S100A7/psoriasin ³⁵S-labeled antisense cRNA. D = higher magnification (400X) of C. E = high magnification (400X) of adjacent section from the same mammary tumor shown in D, hybridized with mouse S100A7/psoriasin ³⁵S-labeled sense cRNA. F = low magnification (100X) of a single tissue section (tissue from a different mouse to that shown in A-E)) hybridized with mouse S100A7/psoriasin ³⁵S-labeled antisense cRNA, where strong focal expression of mouse S100A7/psoriasin RNA is observed in the mammary gland tumor (black arrow) with little or no expression in the surrounding normal mammary gland tissue. B Localization of mouse S100A7/psoriasin expression to areas of squamous differentiation in DMBA-induced mammary gland tumors Sections from formalin fixed paraffin-embedded DMBA-induced mammary tumor samples matched to the frozen tissue from which RNA was previously isolated for RT-PCR analysis were used for in situ hybridization analysis of mouse S100A7/psoriasin expression. A = low magnification (100X) of tumor section hybridized with mouse S100A7/psoriasin ³⁵S-labeled antisense cRNA. B = higher magnification of A (200X), C = high magnification of B. D = adjacent section to that seen in A, B, C, and at same magnification as B but hybridized with mouse S100A7/psoriasin ³⁵S-labeled sense cRNA. E and F are haematoxylin and eosin stains of adjacent sections to that shown in A, B, C, and D. E is the same magnification as in B, and F is the same magnification as that shown in C. Squamous differentiation in the haematoxylin and eosin stained adjacent sections is visualized as a characteristic "pearling" pattern where epithelial tumor cells (purple) differentiate into keratinocytes (pink) before denucleating and sloughing off into the inner lumen (white). Thus cells on the outer margin of the pearled area are undergoing squamous differentiation, and those correspond to cells expressing mouse S100A7/psoriasin RNA, in A, B, and C.