Reflections about Hormone Action and Implications for the Cancer Problem* O. HECHTER (Worcester Foundation for Experimental Biology, Shrewsbury, Mass., and Department of Physiology, Boston University, Boston, Mass.) In his theoretical consideration of hormone ac strates available to integrated mult ¡enzymesys tion, Dr. Mueller has given us the views of a mod tems within semi-isolated compartments of the ern biochemist, conscious of cell organization, cell by regulating the transfer of substrate, or faced with a fundamental problem in cell physiol products, through cytostructural barriers. One as ogy. As an endocrinologist, trained in physiology, pect of this "new view," in essence, amounts to the I find myself in agreement with so much of what rediscovery of the potential importance of perme Dr. Mueller has said that the differences between ability relationships in regulating metabolic se us seem minimal. But differences there are—not so quences, a concept postulated by the pioneers in much in terms of philosophy, but in the delinea pharmacology and cell physiology, with particular tion of profitable areas for future investigation. In reference to the cell membrane. Dr. Mueller's view, the enzyme is the unit of struc For certain reasons, Dr. Mueller has indicated ture and function in the cell, but I cannot help that hormone action upon cytostructural barriers, thinking that this view would not necessarily be while theoretically possible, seems unlikely as a upheld by cytologists, genetists, physiologists, mode of hormone action. I have previously stated pharmacologists, or even by all biochemists. This (12) and still feel that it is precisely in this area, in is a problem in semantics with philosophic over the control of permeability relationships, that we tones, which I do not propose to discuss. I think have the most likely mechanism of hormone ac all would agree that enzymes are important for tion. I readily admit, however, that a host of al cell function, that hormones in one way or another ternative possibilities exist. I should like to discuss modify cellular enzymatic reactions, and that, by a the possible action of hormones at the cell mem study of the manner whereby metabolic sequences brane, particularly with respect to the regulation are regulated in the living cell, hormone action will of growth. From this will arise certain ideas which eventually be elucidated in fundamental terms. may have implications for the cancer problem. I In discussing how and where hormones might shall not restrict this discussion to the steroid hor act at the cellular level, Dr. Mueller listed the old mones exclusively; in my view, the aspect of hor possibilities and some of relatively recent vintage mone action which is of prime importance to the in biochemistry. The old ways, in their essence, are problem of cancer is that which is concerned with those previously discussed by Green in 1940 (8). the regulation of growth of specifically differenti New ideas of hormone action have come into bio ated cells. This trophic action of hormones is not chemistry from a consideration of the enzymology restricted to steroids but is characteristic of the of intracellular structures coupled with the knowl pituitary trophic hormones, of protein or poly- edge from recent advances in cytology (made pos peptid nature as well. If I have broadened the area sible by new technics in electron microscopy), to of discussion by emphasizing that trophic hor gether with an old concept in biology—organiza mones of diverse chemical structure serve a similar tion. From this has emerged the view that hor biological function, I do not wish to imply that a mone action may be concerned with making sub- single mode of action need necessarily be opera * The work described in this paper was supported by The tive. Indeed, as I have previously indicated (12), it Commonwealth Fund, U.S. Army Contract No. DA-49-007- seems more reasonable to expect to find differences MD-546, U.S.P.H. Grant No. RG-4749, and National Science in mechanisms of action where such profound dif Foundation Grant NFS-G-2966. ferences in the chemical structure of the activating Presented at the second meeting of the Scientific Review Committee of the American Cancer Society, held at the West- agents exist. Keeping this reservation in mind, let ehester Country Club, Rye, New York, December 13 and 14, us proceed. 1056. Can hormones act to control permeability relation- 512 Downloaded from cancerres.aacrjournals.org on September 28, 2021. © 1957 American Association for Cancer Research. HECHTER—Reflections about Hormone Action and Cancer Problem 513 ships at the cell membrane?—inthe case of insulin mine whether this is actually the case in diaphragm the answer is almost certainly "yes." There is now muscle in vitro (where an insulin effect upon glu a growing body of evidence that one of the primary cose uptake is well documented), Dr. Resnick and mechanisms of insulin action is to increase the I estimated the rate of sugar penetration (inde transfer of sugar into the cells of certain but not all pendent of secondary metabolic effects) by study tissues (17). Muscle is a key example of an insulin- ing the entry of galactose into the cells of rat dia responsive tissue; brain and erythrocytes are ex phragm muscle, and these studies will soon be pub amples of tissues and cells which do not respond to lished (21). In confirmation of previous reports insulin. According to the hypothesis of Levine and that galactose is not utilized by muscle (17), we Goldstein (17), a "barrier" (probably the cell have established definitively (by analysis of the membrane) normally limits the free entry of sugar radioactivity of COz formed during incubation of into the cell; in responsive tissues insulin acts upon tissue with galactose-C14, as well as by paper a sugar-transfer mechanism to facilitate the pene chromatography of the radioactivity present in the tration of sugar through this barrier where it is tissue and medium) that galactose-1-C14 was not detectably transformed in our system. By deter TABLE 1 mining the content of galactose in the cells at vari INTRACELLULARENTRYOFGALACTOSEIN ous periods of incubation (correcting for tissue DIAPHRAGMMUSCLE extracellular sugar) and employing kinetic equa N*o insulin Insulin Diff. tions derived for us by Dr. A. K. Solomon at (mg/gm/hr) Harvard, it was possible for us to calculate the Resnick and Hechter (al) rate of entry of galactose into the cells in the units No preincubation 1.3 1.4 60 min. preincubation 2.4 4.4 2.0 of mg sugar/gm diaphragm (wet wt.)/hour of in- TABLE 2 GLUCOSEUPTAKEBYDIAPHRAGMMUSCLE CONDITIONS Init. glucose Incubation concentration period No INSULIN1.81.91.61.83.12.5*3.62.71.62.72.21.5iNäCLIX(mg/gm/hr)3.43.52.8S.45.44.3*6.64.52.34.33.82.2Dirr.1.61.61.21.62.31.83.01.80.71.61.60.7 STUDY (mg per cent) (hr.) Gemmili and Hamman (7) 200 3 Stadie (23) 200 2 Villee and Hastings (24) 200 2 Haft et al. (IO) 200 1 \Yalaas and Walaas (25) 140 0.5 U tí U U 140 1.0 Brown et al. (1) 140 0.5 Krahl and Park (16) 140 1 Krahl and Cori (15) 100 2 Perlmutter and Greep (20) 100 2 Li et al. (18) 100 2 Demis and Rothstein (6) 100 1 * The mean of two sets of values presented in the same paper. made available to the intracellular enzymatic ma cubation.The entry rates obtained in these studies chinery. are shown in Table 1; they are compared to rep The nature of this sugar-transfer mechanism resentative studies reported in the literature on upon which insulin acts is still obscure; however, glucose uptake by diaphragm muscle, in the ab certain of its characteristics have been defined. sence and presence of added insulin (Table 2). In Thus, the sugar-transfer mechanism does not ap contrast to galactose (which merely enters and pear to involve a hexokinase-type phosphorylation leaves the cell until the concentration of sugar in step, since the insulin effect occurs with sugars the medium and cells is equilibrated), any glucose which are not metabolized in the test preparation which enters the muscle cell is removed via meta employed; the transfer mechanism has specificity bolic sequences, so that a continuous concentration in that it differentiates between sugars closely re gradient exists. If the transfer rates of galactose lated chemically; moreover, among insulin-respon and glucose entry into cells are of the same order sive sugars (i.e., those sugars whose entry into of magnitude, the values of galactose entry calcu cells is facilitated by insulin) competition exists lated from the kinetic equations should be of the for the transfer mechanism. same order as the rate of glucose uptake by According to the view of Levine and Goldstein, diaphragms, in both the presence and absence of the entry of sugar into the cells is the rate-limiting insulin. Examination of Table 2 shows that in all step in the over-all metabolism of sugar. To deter- the cases cited where diaphragms were incubated Downloaded from cancerres.aacrjournals.org on September 28, 2021. © 1957 American Association for Cancer Research. 514 Cancer Research with 100-200 mg. per cent glucose for 1 hour or sequences), the significance of limiting sugar entry more, this is the case. While it is appreciated that into the cell for DNA and RNA synthesis may be the transfer coefficients obtained with galactose of special significance. If the action of DOC to need not be precisely equivalent to those of glu limit the entry of sugar into the Neurospora cell cose, the fact that the values of glucose uptake has consequences for growth which can be ration reported in the literature are of the same magni alized in terms of established biosynthetic se tude as the values for galactose entry obtained in quences, this is not the case with respect to the our study lends strong support for the view that potassium requirement.