Cloudman melanoma

According to Pawelek et al. 200), the biosynthesis of melanin in Cloudman melanoma cells is a complex process and is regulated by three factors (a) a dopamine conversion factor which converts dopamine to 5,6-dihydroxyindole (13), (b) a 5,6-dihydroxyindole conversion factor which catalyzes the conversion of 5,6-dihydroxyindole to melanin and is active when cells are exposed to melanotropin (MSH), and (c) a 5,6-dihydroxyindole blocking factor which restricts melanogenesis at the 5,6-dihydroxyindole stage. They have also shown that at least three steps in the Raper-Mason scheme of melanin formation from tyrosine are catalysed by tyrosinase (Fig. 6). 

Studies of hypophysectomized todes by Indian workers revealed that psoralen in the absence of light stimulates tyrosinase activity in the skin and liver of toads (13,14). Carter et al. (34) found a 2- to 3-fold increase in tyrosinase activity as compared to psoralen alone after UV irradiation of Cloudman melanoma containing TMP. Borkovic et al. (20), on the basis of their experimental results on melanization with TMP, suggested that TMP may be used in a clinical setting without UV radiation for the... 

It is difficult to generalize from the data available on the reported effects of retinoids on these two related enzyme activities. Results obtained in different cell culture systems are at variance, especially because in certain systems retinoids promote proliferation whereas in others they inhibit it. Moreover, different retinoids have been employed in many of the studies, and the time points chosen for analysis vary from a few hours to several days after the onset of retinoid treatment. For example, Scott and Russell (1982), show a temporal relationship between the peaks of G,-specific ODC and TG activity in synchronized cultures of both CHO cells and murine Cloudman S91 melanoma cells. Retinoid treatment (10 A/ retinol in the case of the CHO cells 10 A/ retinoic acid for the... 

Many attempts have been made to develop transplantable tumours as models for the study of specific human cancers. Thus, the Cloudman S91 melanoma was developed to select drugs for use in the treatment of human melanoma [9], and plasma cell tumours as models for multiple myeloma [10], The greatest disadvantage of this approach is that tumours tend to lose their special characteristics very rapidly during serial transplantation, with the result that the tumour obtained is similar to those originating from different tissues. An extension of this approach would be the matching of human cancers with transplantable tumours having similar enzyme content and other biochemical features. 

Oosterhuis JW, Verschueren RCJ, Eibergen R, Oldhoff J. The viability of cells in the waste products of C02-laser evaporation of Cloudman mouse melanomas. Cancer 1982 49 61-67. 

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