Optimal conditions for immunohistochemical determination of the in vitro DNA synthesis labelling index with bromodeoxyuridine in head and neck cancer

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.

Improved methodology for detecting bromodeoxyuridine in cultured cells and tissue sections by immunocytochemistry

Detection of DNA synthesizing cells may often be achieved by immunocytochemical detection of bromodeoxyuridine (BrdU), which is rapid and appears to give similar results to those found using tritiated thymidine. However, the methodology for detection of BrdU involves a denaturation or digestion step to allow access of the antibody to BrdU incorporated into single- rather than double-stranded DNA. We wished to determine if microwave treatment could be used to enhance the detection of BrdU without the need for any other digestion/denaturation steps. An important consideration was to investigate whether such treatment produces a similar quantitative result, since BrdU detection is usually assessed on the basis of cell number rather than topographical distribution. We have found that microwave treatment can allow considerably lower antibody concentrations and eliminates the need for any other denaturation step. It also reduces the non-specific background staining found when using monoclonal antibodies on mouse tissue. We have performed cell counts and found that the number of BrdU positive cells remains constant for a range of different immunocytochemical parameters. We also report conditions where immunopositivity is adversely affected by changes in technique and describe the optimised conditions for obtaining reproducible results.

Comparison of isotopic and immunohistochemical methods of studying epithelial cell proliferation in hamster tongue

Our purpose was to validate different approaches to the study of cell proliferation in stratified squamous epithelia, using oral mucosa as a model. Dorsal and ventral tongue from the hamster were examined following in vivo labelling with tritiated thymidine and bromodeoxyuridine (BrdUrd), and in vitro labelling with BrdUrd. These were compared with direct immunolabelling of fixed tissue sections with monoclonal antibody PC10. For the former methods S phase cells were quantified following autoradiography or immunohistochemistry. We conclude that the proliferative status of simple, flat, lining mucosae such as ventral tongue can be derived by all three pre-labelling methods and, on average, 18-19 cells per surface millimetre length were in DNA synthesis. On the other hand dorsal tongue epithelium, which is thicker, has an undulating morphology and a complex cell renewal pattern, gives different results with the three labelling methods. In both sites the proliferating cell nuclear antigen (PCNA) index was fourfold that obtained by nucleotide labelling. This is consistent with PCNA marking proliferative cells in other phases of the cell cycle in addition to the S phase. Thus, there are potential differences between the information on proliferative status derived by PCNA immunohistochemistry and other established cell cycle markers, which need to be taken into account in the interpretation of epithelial cell kinetic data in health and disease.

Morphine regulates DNA synthesis in rat cerebellar neuroblasts in vitro

The effects of morphine on DNA synthesis by external granular layer (EGL) neuroblasts was examined in whole-mount organotypic cultures isolated from 10-day-old rat cerebella using bromodeoxyuridine (BrdU). After 24 h in vitro, explants were treated for 24 h with 10 nM, 1 or 100 microM morphine, morphine plus 30 nM, 3 or 300 microM of the opiate antagonist naloxone, respectively, or those concentrations of naloxone alone. BrdU was added during the last 4 h of drug treatment. EGL neuroblasts were unambiguously identified by size and morphology, location and by protein kinase C II immunocytochemistry. The proportion of EGL neuroblasts incorporating BrdU was significantly reduced in the presence of 1 microM morphine, while 100 microM morphine had little additional effect. The concentration of morphine predicted to cause a half-maximal reduction in BrdU labeling index was 22.5 nM. Morphine's ability to reduce BrdU incorporation by EGL neuroblasts was concentration dependent and was prevented by concomitant treatment with naloxone, implicating the involvement of opioid receptors. The results suggest that morphine can directly regulate the growth of the developing cerebellum by inhibiting neuroblast proliferation within the EGL.