20-OH-Ecdysone-induced morphogenetic movements in a Chironomus cell line are accompanied by expression of an embryonic muscarinic system

Muscarinic receptors in cell lines from ovarian carcinoma: negative correlation with survival of patients

OBJECTIVES

Tumor cells are similar in many respects to embryonic cells, indicating that embryonic genes are reactivated during malignant growth. In previous studies, we observed muscarinic acetylcholine receptors, which are expressed in embryonic cells during morphogenesis and are also found in human melanomas and melanoma cell lines. We determined the presence of muscarinic receptors in a collection of ovarian tumor cell lines for which clinical data were available.

METHODS

Muscarinic receptor status of 39 cell lines derived from 34 patients was determined by Western blotting.

RESULTS

Twenty-three cell lines were receptor positive, and 16, receptor negative. Kaplan-Meier analysis of receptor status of the tumor cell lines and survival time of patients from which the cell lines were established showed that expression of muscarinic receptors was associated with a reduced probability (P = 0.025) of survival: This is within the range of other established prognostic factors reported in the literature.

CONCLUSIONS

A large percentage of ovarian tumor cell lines express muscarinic receptors. Muscarinic receptor expression is an embryonic trait and is correlated with reduced survival of patients. The results from this study provide further evidence of the involvement of muscarinic receptors in the progression of malignant carcinomas.

Immunohistochemical localization of ecdysteroid receptor and ultraspiracle in the epithelial cell line from Chironomus tentans (Insecta, Diptera)

Ecdysteroid receptor (EcR) and its heterodimerization partner, ultraspiracle (USP), were demonstrated in the epithelial cell line from Chironomus tentans by immunohistochemistry. In untreated cells both proteins are present in nuclei as well as in granular compartments of the cytosol. At 1 day after addition of 1-microM 20-OH-ecdysone (20E) total immunofluorescence had increased in the nuclei, whereas the cytoplasmic staining had disappeared. At the 2nd and 3rd days all cells within a vesicle appear identical according to morphological criteria, but the EcR and USP immunoreactivity becomes restricted into patches of neighbouring cells. The hormonally induced changes in the pattern of localization of functional ecdysteroid receptor, the heterodimer of EcR and USP, are discussed in relation to similar effects of 20E on acetylcholinesterase and muscarinic acetylcholine receptor distribution in this cell line.

Ecdysteroid resistant subclones of the epithelial cell line from Chironomus tentans (Insecta, Diptera). I. Selection and characterization of resistant clones

Chironomus tentans cells were cultured in the presence of gradually increasing concentrations of 20-OH-ecdysone or a nonsteroidal molting hormone agonist, the benzoylhydrazine RH 5992, for a period of about 2 yr. From these cultures, subclones were selected, which are resistant to up to 25 microM 20-OH-ecdysone according to morphological (changes in cell shape and cell arrangement) and physiological criteria (acetylcholinesterase induction, secretion of chitinolytic enzymes, thymidine incorporation). Some subclones, selected in the presence of 20-OH-ecdysone, are resistant only to molting hormone, but still respond to RH 5992 morphologically and biochemically, whereas subclones selected in the presence of the benzoylhydrazine showed no reaction neither to 20-OH-ecdysone nor to the hormone agonist. Hormone resistance is stable; 3 mo. after hormone withdrawal, resistant clones still do not respond to renewed exposure to 20-OH-ecdysone or RH 5992, respectively. Because in all resistant subclones tested so far all hormonally regulated responses known from sensitive cells were no longer detectable, it is assumed that the hormone signaling pathway itself is interrupted. Possible mechanisms of hormone resistance were discussed.

Immunohistochemical localization of muscarinic acetylcholine receptors in primary and metastatic malignant melanomas

In embryos morphogenetically active cells transiently express the cholinergic system comprising cholinesterase activity and muscarinic acetylcholine receptors. Malignant melanomas develop from melanocytes, which are derived from the neural crest. Neural crest cells express the embryonic muscarinic system during migration. Using the monoclonal antibody M35, we now show that normal melanocytes carry no muscarinic receptors, whereas malignant melanoma cells express them again. In primary melanomas and metastatic melanomas, we identified muscarinic receptors in solid strands or groups of atypical cells. In all primary malignant melanomas studied we found inhomogeneous distributions of M35-immunoreactivity subdividing the tumors into three different zones. In the tumor center, groups or single cells often showed only little or even no immunofluorescence. In contrast, pericentrally we detected strong immunostaining in the conglomerations of atypical melanocytes. In the peripheral infiltration zone, intensely fluorescent cells in clusters or single, were spreading into the normal tissue, leading to a more patchy staining pattern. Melanocytes of nevi also possess muscarinic receptors, showing similar distribution patterns as in the melanoma. We suggest that in malignant melanomas muscarinic receptors might play a regulative role in infiltrative growth and metastasis.

A muscarinic acetylcholine receptor, present in the epithelial cell line from Chironomus tentans

A muscarinic cholinergic receptor (mAchR) is present in the non-neuronal epithelial cell line from Chironomus tentans. Scatchard plot analysis (KD = 1.4 nM) using the non-selective antagonist quinuclidinylbenzilate (QNB), as well as kinetic data (KD = 1.7 nM), reveals one class of high affinity binding sites. About 2000 binding sites/cell are present. The receptor concentration (54.5 +/- 7.5 fmol/mg protein) is comparable to the values reported from insect brain. The receptor interacts only with muscarinic ligands; nicotinergic acetylcholine receptors are not present. Binding properties are not comparable to any of the muscarinic subtypes known from vertebrate tissues. The rank order of competition of radiolabelled QNB is: QNB > atropine > PrBCM > oxotremorine, pirenzepine > methoctramine. The competition curve obtained with carbamylcholine is shifted to higher ligand concentrations in the presence of Gpp(NH)p and to lower carbamylcholine concentrations by 1 mM NEM. With antibodies against muscarinic receptor from calf brain one band with a molecular weight of about 80 kDa is detected on Western blots. The moulting hormone 20-OH-ecdysone transiently increases the concentration of muscarinic receptor.