Induction of squamous metaplasia: requirement for cell multiplication, and competition with lobuloalveolar development in cultured mammary glands

Tumour-simulating squamous cell metaplasia (SCM) in necrotic areas of salivary gland tumours

Squamous cell metaplasia (SCM) adjacent to necrotic areas of salivary gland tumours must be distinguished from other types of SCM (focal SCM in the excretory ducts of salivary glands; necrotizing sialometaplasia; focal SCM within salivary gland tumours) in respect to the tissue structure. Based on the high cellular proliferation, arcade- or cord-like pseudoneoplastic SCM develops with stellate extension in the surrounding tissue and focal inclusion of goblet cell metaplasia. This proliferative SCM resembles the cellular demarcation of radicular dental cysts. In the Salivary Gland Register 8 cases of tumor-simulating SCM could be analysed which clinically and morphologically were suspect of squamous cell or mucoepidermoid carcinoma. Five cases were localized in the parotid gland, 2 cases in the submandibular gland and 1 case in the palatinal glands. Tumour-simulating SCM was developed in pleomorphic adenomas (5 cases) and in multifocal adenomatous oncocytic hyperplasia (3 cases).

A general native-state method for determination of proliferation capacity of human normal and tumor tissues in vitro

An important need in cancer research and treatment is a physiological means in vitro by which to assess the proliferation capacity of human tumors and corresponding normal tissue for comparison. We have recently developed a native-state, three-dimensional, gel-supported primary culture system that allows every type of human cancer to grow in vitro at more than 90% frequency, with maintenance of tissue architecture, tumor-stromal interaction, and differentiated functions. Here we demonstrate that the native-state culture system allows proliferation indices to be determined for all solid cancer types explanted directly from surgery into long-term culture. Normal tissues also proliferate readily in this system. The degree of resolution of measurement of cell proliferation by histological autoradiography within the cultured tissues is greatly enhanced with the use of epi-illumination polarization microscopy. The histological status of the cultured tissues can be assessed simultaneously with the proliferation status. Carcinomas generally have areas of high epithelial proliferation with quiescent stromal cells. Sarcomas have high proliferation of cells of mesenchymal organ. Normal tissues can also proliferate at high rates. An image analysis system has been developed to automate proliferation determination. The high-resolution physiological means described here to measure the proliferation capacity of tissues will be important in further understanding of the deregulation of cell proliferation in cancer as well as in cancer prognosis and treatment.

Characterization of the calcium sensitivity of differentiation in SCC-13 human squamous carcinoma cells

The sensitivity to calcium of the human squamous carcinoma cell line, SCC-13, was demonstrated and characterized. Cultures grown to confluence in the presence of 0.2 to 2 mM calcium had approximately 10-fold higher levels of particulate transglutaminase activity and envelope competence than those grown in low calcium (0.025 to 0.05 mM) medium. Raising the calcium from 0.025 to 1.8 mM induced expression of this enzyme and of competence over the course of a week. Conversely, for cultures grown to confluence in 1.8 mM calcium, subsequent reduction of calcium to 0.025 mM resulted in a substantial decline in transglutaminase over a similar time period. Immunoprecipitable transglutaminase was clearly identifiable in cultures grown in 1.8 mM calcium-containing medium but not in those grown in low calcium medium or in the presence of retinoic acid, suggestive of regulation at the level of mRNA accumulation or translation rather than posttranslational modification.

Induction of keratinocyte type-I transglutaminase in epithelial cells of the rat

Using immunogold-silver techniques, we have demonstrated that, in rats, type-I (keratinocyte) transglutaminase is expressed primarily in stratified squamous epithelia of the integument, the upper digestive tract, and the lower female genital tract. In these epithelia, the enzyme was found to be present predominantly in the granular layer, but was evident at low levels even in the basal layer, especially in the genital tract. No immunoreactivity was detected in glandular, columnar, or transitional epithelia or in soft tissues. However, considerable enzyme antigenicity was observed in the endometrium and in major ducts of the pancreas and mammary glands of near-term pregnant and early postpartum females. In cultures, substantial immunoreactivity was readily identifiable not only in epidermal, vaginal, and esophageal epithelial cells (immunopositive in vivo), but also in urinary bladder, seminal vesicle, and tracheal epithelial cells (immunonegative in vivo). Primary epithelial outgrowths from bladder and seminal vesicle tissue explants were immunopositive, demonstrating rapid adaptation to the culture environment. These results reveal three distinct levels of regulation of transglutaminase expression in various cell types: during the differentiation of keratinocytes, during pregnancy, being evident principally in the endometrium but detectable elsewhere as well, and during the cultivation of certain epithelia which do not normally express the enzyme in vivo. We conclude that type-I transglutaminase may be a valuable marker for elucidating the regulation of normal epithelial differentiation and squamous metaplasia.

Hormonally induced elevations of alpha- and beta-casein mRNA levels are blocked by cyclic adenine nucleotide and prostaglandins

Normal mammary gland development during pregnancy follows a coordinated program of morphological development (formation of lobuloalveoli) and biochemical differentiation (casein production). In culture, whole mammary glands of Balb/c mice can be similarly induced by application of a mixture of insulin, prolactin, aldosterone and hydrocortisone (IPAH) for 7 days. Our previous reports have shown that lobuloalveolar development, induced by IPAH, is competitively inhibited by the simultaneous presence of dibutyryl cyclic AMP (Bt2cAMP), prostaglandins (PGs) E1, E2, and B1, and papaverine (pap). However, if this mixture is not added until day 4, lobuloalveolar development is relatively unaffected but casein synthesis is repressed. This report explores the mechanism by which cyclic adenine nucleotides and prostaglandins interfere with the normal developmental pathway. The accumulation of alpha- and beta-casein mRNAs induced by prolactin, hydrocortisone and aldosterone is blocked by the combination of Bt2cAMP, PGs E1, E2, and B1, and pap added to the medium for the final 3 days (days 4-7). Under these conditions the glands retain their lobuloalveoli, and little squamous metaplasia can be discerned. Furthermore, de novo synthesis of both caseins is selectively inhibited, despite the continued presence of casein mRNAs in the glands and normal protein synthesis. In contrast, the synthesis of keratin is stimulated. Incomplete mixtures of Bt2cAMP and pap or the combination of PGs E1, E2, and B1, are only partly effective in preventing the accumulation of casein mRNAs. All three mixtures bring about similar effects on both alpha- and beta-casein mRNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural features of bovine mammary epithelial cells grown on collagen gels

Bovine mammary epithelial cells cultured on floating gels of rat tail collagen showed two principal cell types, columnar and squamous, with ultrastructural features resembling secretory and myoepithelial cells respectively. Cultures of freshly prepared cells released alpha-lactalbumin into the culture medium and in some cases contained fat droplets, although these did not appear to be released. No ultrastructural evidence of casein synthesis was observed. A notable feature was the failure to secrete a continuous basement membrane. Intermediate filaments were present in abundance in squamous epithelial cells.