Influence of omega-3 fatty acids on the growth of human colon carcinoma in nude mice.

The present study investigated the influence of dietary omega-3 fatty acid supplementation on the growth of human colon carcinoma xenograft in athymic nude mice. Four diets were fed to evaluate the effect of levels and types of fat on colon tumor growth. Animals were maintained on a standard diet modified by addition of fats containing omega-3 and omega-6 fatty acids to represent high and low fat intakes for 53 days. The final mean estimated tumor weight for the high fat corn oil (24%) fed group was 2,302 mg, whereas the low fat (8% corn oil) group was 1,681 mg. The final mean tumor weight of the high fat menhaden oil fed group was 782 mg representing a 66% decrease in growth compared to the high fat corn oil group and a decrease of 54% compared to the low corn oil fed group. The high fat golden algae oil fed group resulted in a mean final tumor weight of 223 mg representing a 90% inhibition of tumor growth relative to the high fat corn oil fed group and 87% inhibition of growth compared to the low fat corn oil fed group. These findings indicate that dietary omega-3 fatty acids possess significant tumor suppressing properties and that the primary tumor suppressing fatty acid is docosahexaenoic acid. Histopathologic examination of control and treated tumors and expression array analyses (human cytokine and apoptosis arrays) support the tumor growth inhibition data and provide evidence for discussion of possible mechanisms for the observed growth inhibition.

Biochemical formulations of embryonic gene control.

A search for control mechanisms involving embryonic genes is explored reviewing a variety of subject areas including, a) the methylation status of DNA and the globin gene, b) ethionine and steroid effects on expression of embryonic genes, c) alpha-fetoprotein gene activity induced by carcinogens and in hepatomas. Also taken into account are transcriptional and cytogenetic aspects. Theories of heterochromatin dynamics are developed in connection with certain contributions from chromatin experimental findings, especially regarding the status of methylation. The potential importance to control theory of the inverse correlation between ATP:L-methionine S-adenosyltransferase activity and alpha-fetoprotein synthesis is emphasized. Several generalizations were derived during the study. It appears that the depression mechanisms may act only on genes that have been active in embryonic stages and have become repressed during differentiation. Another idea concerned heterochromatin. Any heterochromatic segment of DNA may represent at its associated ends a certain amount of euchromatin that would be in a quasi-heterochromatic state. Such pseudoheterochromatin is hypothesized to be induced by the true heterochromatin (eigenheterochromatin).

A specific mechanism for ethionine-induced embryonic gene activity.

A specific mechanism was given for ethionine-induced alpha-fetoprotein gene activity and is as follows: 1. Ethionine acts on competent cell types (e.g. stem cells) having one alpha-fetoprotein-enhancer-albumin gene region that is active and possesses embryonic-like low levels of S-adenosyl-L-methionine synthesis: DNA methylase genes for the enhancer regions are in the heterochromatic state. 2. ATP: L-methionine-S-adenosyltransferase acts upon ethionine and ATP to form S-adenosyl-L-ethionine; this lowers the amount of S-adenosyl-L-methionine synthesized and in turn also the synthesis of methyl-nicotinamide; the concentration of nicotinamide increases; there is an inhibition of polyADP ribosylation; hyporibosylation of histone 1 of nucleosomes; deblocking of embryonic type heterochromatin; and finally the second alpha-fetoprotein gene becomes activated. 3. Reversal occurs with the introduction of methionine; increase of S-adenosyl-L-methionine synthesis; increased methylnicotinamide synthesis; increased polyADP-ribose synthesis; ribosylation of H-1 protein to normal levels; and then the packing configuration of chromatin causes rerepression of alpha-fetoprotein genes. It is suggested that ethionine has the ability to perturb a methyl-sensitive heterochromatin that is peculiar to chromatin synthesized during embryogenesis. Therefore such repressed embryonic genes as alpha-fetoprotein are differentially susceptible to low concentrations of active methyl groups. Ethionine causes this hypomethylated heterochromatin by interference with S-adenosyl-L-methionine synthesis.

Derivation of a basic mechanism of control for embryonic genes as a specific subset.

The alpha-fetoprotein gene is conceived as being methylated in the zygote and according to the model is in a heterochromatic state and is therefore in a non-functional condition. Specific DNA methylase genes would produce methylases capable of alkylating enhancer regions of alpha-fetoprotein and certain proteins that would alter the heterochromatin condition. Also involved is a gene for the synthesis of a conformational-inducer protein that is proposed to be capable of blocking genic regions from reheterochromatizing. One of the pivotal events is the accumulation of S-adenosyl-L-methionine that reaches intracellular pool concentrations allowing other redundant active S-adenosyltransferase genes to become active. During embryogenesis specific conformational-inducer proteins would block genes such as the gene for albumin from reheterochromatizing while alpha-fetoprotein gene becomes heterochromatized during subsequent cell cycles. This heterochromatin is formed with embryonic type proteins sensitive to ribosylation-induced conformational changes. The increase in synthesis of alpha-fetoprotein followed by a decrease as albumin synthesis increases during embryogenesis is predicted by the scheme.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXVI. Evolutionary significance of carcinogen-induced embryonic gene activity.

Besides the major theme of this series of writings--that chemically derepressed embryonic genes are fundamental to the mechanisms of carcinogenesis, there appear to be other significant aspects to this process. Yeast cells have the ability to differentially respond to carcinogens and non-carcinogens by the activation of embryonic type genes that are also found in mammals. This strange relationship is interpreted here as being due to certain phylogetically conserved genes from yeasts existing also in mammals that are used in both organisms for the same process. For example, a protooncogene found in yeast cells or embryonic cells serves for rapid mitosis. Also yeast mating type genes have high homologies to homeotic domains and therefore may be prototype genes of homeotic genes, which are embryonic type genes in animals.

Generalizing the control process for embryonic genes.

Embryonic genes are considered as a separate subset of genes with unique chromatin properties. There is a problem of defining the duration of perturbations of embryonic gene activity that has been chemically induced and the normal relatively longer lasting changes that occur during differentiation. This problem may be related to unique properties of the chromatin of embryonic genes. Methylation of DNA is thought to be only one level of control and the superstructure of chromatin involving heterochromatin is of equal importance to embryonic gene expression. Proto-oncogenes are considered to be embryonic type genes whose activities are regulated under the same mechanisms by which other embryonic genes are regulated. Control aspects are discussed in the light of i) repressor-derepressor and blocking-deblocking mechanisms, ii) activator genes, pseudogenes, LINES, SINES, v-type position effects, iii) effects of ethionine, and iv) steroid hormone effects especially with respect to a subset of repeated rRNA genes which are considered to be structured in embryonic type chromatin.

Maintenance of embryonic gene activity into the adult state.

It is now apparent that certain embryonic gene activities may be maintained before the transition from embryonic to the adult state takes place. The consequence of such a condition could have far reaching results and create a totally new approach to biotechnology by dealing with epigenetic methods and not gene-splicing methods. For example, if a group of c-oncogenes, believed to be of the embryonic type (1) that are responsible for growth factors which regulate embryonic rates of growth, then large increases in growth rates during the adult stage should occur. Two major alterations seem to be required. One is the interference of DNA methylation patterns using such agents as ethionine (interfering with S-adenoysl-1-methionine synthesis) or azacytidine (interfering with DNA methylase activity). Secondly, a change in chromatin configuration (deheterochromatization?) with agents such as n-butyrate or hexamethylenebisacetamide (HMBA). Maintenance methylases would make the altered (hypomethylated) pattern of the perturbed chromatin invariant after the initial perturbation. Enhancer-promoter mechanics are probably pertinent to this process.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXVIII. Intermediate generalizations (Part C).

This is the final section of an intermediate phase of generalizations dealing with aspects of enhancers. It is concluded that a binding type protein(s) complex near a LTR segment. This creates destabilization of heterochromatin that allows transcription mechanisms. If this process is promoted by anomalous enhancer activity such as those produced by chemical inducers which modify chromatin states or cause hypomethylated enhancer regions, then normally repressed embryonic gene products, such as protooncogene growth factors, can be transcribed inappropriately to a specific developmental stage, eg post-embryonically.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXVII. Intermediate generalizations (Part B).

In this second section of generalizations, methylation, differentiation and carcinogenesis are reviewed. Special consideration is given to the alpha-fetoprotein gene which is used extensively as a model embryonic gene. Specific correlations are made between the glucocorticoid response element and the alpha-fetoprotein gene. A further correlation was made between retinoic acid and alpha-fetoprotein synthesis.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: intermediate generalizations.

A previous rendition of a mechanism for the induction of embryonic gene activity, derived from the viewpoint of agents capable of such inductions, concluded that a perturbed methylation pattern of DNA and/or chromatin proteins would be an essential feature. A more specific treatment of the mechanism centers on enhancer regions of proto-oncogenes as being the point of modification for any induction of new gene activity. DNA binding type proteins may be involved with deheterochromatization processes after complexing near long terminal repeat segments containing enhancer elements. Chemical carcinogens and steroids would modify the chromatin and directly or indirectly interfere with maintenance DNA methylation. The resulting hypomethylated enhancer and promoter regions would allow for enhancer mechanisms to activate repressed embryonic genes inappropriate to the developmental stage forcing embryonic features to be expressed by differentiating (or differentiated) cells.

Hereditary and environmental influences on blood pressure values of premenopausal women and their college-age daughters.

Blood pressure (BP) and environmental (dietary/lifestyle) variables were measured in 62 healthy normotensive pairs of premenopausal mothers (44.3 years) and their college-age consanguineous daughters (18.7 years) to estimate the relative contributions of genetic vs environmental factors on BP. As expected, the mothers had significantly higher systolic (SBP) and diastolic (DBP) blood pressures than the daughters (p less than 0.004 and 0.012, respectively). Among the dietary/lifestyle variables measured, mothers were found to have significantly higher mean weight and body mass index (BMI) (p less than 0.009 and 0.001, respectively), and significantly lower lean body mass (LBM) and calcium intake than their daughters (p less than 0.003 and 0.037, respectively). Significant correlations were found between mean BP of the mothers and their mean weight and BMI. No significant correlations existed for the daughters. The familial resemblances between BP of the mothers and daughters were relatively low, i.e., 0.14 for SBP and 0.19 for DBP. From these findings we conclude that the higher BP values with increased age among this healthy female population primarily result from an increase in BMI and a shift from lean to fat mass, as measured by midarm circumference. Our results suggest that environmental factors, i.e., excessive energy intake over time, accompanied by decreased physical activity, are primarily responsible for the greater indices of body fat and the higher BPs observed in this sample of healthy premenopausal women.

PIP: Blood pressure (BP) and environmental (dietary/lifestyle) variables were measured in 62 healthy, normotensive pairs of premenopausal mothers (44.3 years) and their college age consanguineous daughters (18.7 years) to estimate the relative contributions of genetic vs environmental factors on BP. As expected, the mothers had significantly higher systolic (SBP) and diastolic (DBP) BP than the daughters (p0.004 and 0.012, respectively). Among the dietary/lifestyle variables measured, mothers were found to have significantly higher means for smoking cigarettes and using oral contraceptives; weight and body mass index (BMI; p0.009 and 0.001, respectively), and significantly lower lean body mass (LBM) and calcium intake than their daughters (p0.0003 and 0.037, respectively). Significant correlations were found between mean BP of the mothers and their mean weight and BMI. No significant correlations existed for the daughters. The familial resemblances between BPs of mothers and daughters were relatively low, i.e., 0.14 for SBP and 0.19 for DBP. From these findings, the authors conclude that the higher BP values with increased age among this healthy female population primarily result from an increase in BMI and a shift from lean to fat mass, as measured by midarm circumference. The results suggest that environmental factors, such as excessive energy intake over time, accompanied by decreased physical activity, are primarily responsible for the greater indices of body fat and the higher BPs observed in this sample of healthy premenopausal women.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXIV. Repeated embryonic genes in liver.

Many embryonic genes may be sets of repeated genes. Processes of differentiation where the quantity of gene activity changes during embryogenesis may not reflect the transcription rate per se but instead be a result of the state of expression of constitutive repeated genes. Such repeated genes (in fact or theory) is dealt with here for embryonic, adult and neoplastic liver. Explanations are presented for 1) the variation in ATP: L-methionine S-adenosyltransferase activity in spontaneous hepatomas and embryonic liver; 2) differences tRNA L-methionine S-adenosyltransferase activity in spontaneous hepatomas and embryonic liver; 3) differences in tRNA methylase activity in embryonic liver, hepatomas of varying levels of differentiation, and ethionine treated liver; 4) relationships between rRNA genes and nucleolar organizers; and 5) the possibilities involving c-onc genes (proto-oncogenes) for situations of 'over-expression' in neoplastic and embryonic liver.

Mecanismo teórico de la hepatocarcinogénesis / Theoretical mechanism of ethionine hepatocarcinogenesis

En resumen, parece ser que el proceso necesario, al menos conceptualmente que le permita a uno construir una noción adecuada del mecanismo involucrado durante la carcinogénesis inducida por etionina, puede ser relevante a un proceso más general y fundamental aplicable a todos los carcinógenos. Se ha descrito un intento que trata de aportar un mecanismo considerado en este artículo, también enfatiza la importancia de la activación de proteínas embriónicas como un ejemplo de un proceso más general que se requiere para la carcinogénesis

Familial resemblance of radial bone mass between premenopausal mothers and their college-age daughters.

The influences of heredity and environmental factors on radial bone mass were evaluated in 84 premenopausal mothers with their biological daughters (ages 18-22). Mid- and distal radial bone mineral content (BMC) and density (BMD) were assessed using single-photon absorptiometry. As a group, the daughters (mean age 18.6 years) had 5-10% less bone mass at both the distal and midradial sites than their mothers (mean age 44.2 years). Familial resemblance estimates showed significant relationships between mothers and daughters for mid- and distal BMC and BMD after considering the influence of body mass index (BMI). Daughters with a maternal family history of osteoporosis had 6-7% lower but nonsignificant values of mid- (P = 0.086) and distal BMC (P = 0.075) compared to values of women with a negative family history, whereas mothers with a positive family history had 3-4% lower (NS) values of distal and mid-BMC compared to those of mothers with a negative family history after adjustment for BMI. Multiple regression analyses showed BMI to be the most important determinant of the bone values of the mothers, and both BMI and dietary calcium intake were found to be significant for the daughters. The findings of this study suggest that hereditary contributions from the mothers play an overwhelmingly critical role in the accrual of bone mass by their daughters by ages 18-22, but that environmental influences on bone consolidation during the premenopausal decades may be more important in promoting optimal (peak) bone mass and thereby may help to delay the postmenopausal onset of osteoporotic fractures.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXIII. Enhancer theory.

Embryonic gene enhancers may be controlled by deheterochromatization of genes of trans-acting factors caused by altered methylation states of hypersensitive chromatin. Such specific chromatin sites would have a certain required helical pitch (X-type DNA). Non-core regions surrounding the enhancer motif would allow interactions with specific cell type promoters. Differences in embryonic and adult type genes may be reduced to these enhancer activities and certain trans-acting proteins effecting these genic control elements. Furthermore all spurious embryonic gene activities of neoplasms may also be due to such factors. Even pleotrophic and cascade phenomena in dysdifferentiation processes may be described in terms of enhancer mechanisms. Duplications of enhancer sequences may be fundamental to the potential of hyperactivity by embryonic type genes. Examples of this would be alpha-fetoprotein correlations with enhancer activity and possibly increased nucleolar organizer activity of embryonic cells. The manner by which chemical carcinogens would be involved with enhancer processes would be via "key" mechanisms that have been presented previously.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XXII. Key theory--a mechanism for enhancer function.

In summary the Key Theory states that certain planar molecules can act in latching together enhancer elements with promoter elements to create hypersensitive recognition for super-efficient initiation sites of RNA polymerase activity of a specific structural gene. Specificities of these key molecules are required because of transacting factor binding and minor groove steric relationships and/or alkylations that in turn forms relatively permanent "on" modes of gene activity. This presents an explanation for the mechanism of a great variety of biologically active molecules such as steroid hormones and carcinogens.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic protein: XXI. Oncogenes interpreted as embryonic genes.

If oncogenes are interpreted as embryonic genes then the mechanisms for induction of these embryonic genes can be generalized and theoretical considerations can be derived as follows. Agents that induce activity by derepressing embyronic genes can be placed into major groups: i) translocation inducers, ii) non-mutating carcinogenic agents, iii) intercalating DNA groove distorters, and iv) mutating agents. Translocation inducers work via long terminal repeat insertions, antibody promoter region associations, or V-type position effects. Non-mutational agents such as ethionine cause hyporibosylation of nucleosome core histones or hypomethylation of promoter regions of conformation inducer proteins. All of these agents cause deheterochromatizations of facultative heterochromatin. These processes (or by a classical mutation with mutating agents), cause DNA replication to acquire a new abnormal methylation pattern that is held constant by maintenance DNA methylases. The resultant active series of repressed reduntant type embryonic genes, such as subsets of rDNA genes and tRNA methylase genes, including oncogenes, e.g., protein phosphokinases among other required genes, and spurious irrelevant embryonic genes to the process of carcinogenesis. From the above theory is derived the concept that normal sets of redundant genes, e.g., rDNA are normally activated by planar intercalating agents (steroids) that would simply be the limiting subset of the mechanism used to create an anomalous state when extended to the set of embryonically repressed genes that become activated.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XX. Embryonic gene perturbations expressed in terms of matrix algebra.

Simple matrix expressions can be devised for gene repressor associations that lend themselves to manipulations such as linear transformation matrices. Such transformation matrices act in perturbing representations for given repressed genic states and may be analogous to carcinogens. Although the matrix algebraic expressions are developed by using simple repressor theory, it can equally serve to represent modifications of chromatin domains that may be more consistent with mechanisms of derepression of embryonic genes. In general, it is proposed that the potentially exploitable algebras such as abstract, geometric, matrix, vector and tensor be a subset of mathematical biology termed "Bioalgebraic Field Theory".

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: XIX. Embryonic genes.

The methylation status of a conformation-inducer protein that would effect the status of DNA in relation to its ability to be in an active or inactive state is proposed to be central in the regulation of embryonic genes. Thus a distinction can be drawn between induceable "adult" genes such as glucocorticoid induced tyrosine aminotransferase and induceable "embryonic" genes such as ethionine induced alpha-fetoprotein. However, in the proposed mechanism the methylation of DNA is also important in that a hypomethylated state of a CCGG sequence of a promotor region for a conformation-induced protein gene is required to initiate the induction events.