CR-increase longevity not related to position in evolution?

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Hi All,

This post describes:

Hursting SD, Lavigne JA, Berrigan D, Donehower LA, BJ, Phang JM, Barrett

JC,

Perkins SN.

Diet-gene interactions in p53-deficient mice: insulin-like growth factor-1 as a

mechanistic target.

J Nutr. 2004 Sep;134(9):2482S-2486S. Review.

PMID: 15333746

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve & db=pubmed & dopt=Abstra\

ct & list_uids=15333746 & query_hl=19

Only the corrupted pdf is available for the paper. However, it seemed that an

overlooked result that was the Table 1 showed possibly remarkable findings

regarding

how much CR increased the longevity of various species, some with mutations.

There

was an apparent lack of correlation for the evolutionary ladder positions of the

species and their % longevity increased by CR. Therefore, does this data

provide

encouraging information regarding how long CRers will live?

The legend to the figure is:

FIGURE 1 Increased longevity associated with calorie restriction (CR) in

diverse

model species, including p53 knockout mice (refs. 8–18). These studies involve

30–40% CR with 3 exceptions: 1) Yeast were reared on 2% vs. 0.5% Glucose media

(Lin

et al., 2002); 2) Worm data were obtained by comparing strains with genetic

defects

in feeding rate with control strains (Lakowski and Hekemi, 2000); 3) Zucker rats

were restricted 18% relative to controls ( et al., 1997).

There appears to be an error in the legend X-axis units. The % increase in

longevity is only in the single digits. Assuming this error results in the

values

being low by a factor of 10, the eye-ball-determined values for the various

species

for FIGURE 1 were:

Mutation/species % CR-increased longevity

...........................................

Drosphila 10

Labrador retriever 18

C. elegans 25

Yeast 27

C3B10RF1 mouse 28

Sprague Dawley rats 34

Hereford cow 35

p53^+/+ mouse 37

F344 rat 39

p53^-/- mouse 46

Zucker rat 47

Spider 53

Lep^Ob/Ob mouse 57

The references 8-18 for the sources from which the data was taken, and a number

of

which references are pdf-available, are:

8. Cancer Res. 1997 Jul 15;57(14):2843-6.

Calorie restriction induces a p53-independent delay of spontaneous

carcinogenesis in

p53-deficient and wild-type mice.

Hursting SD, Perkins SN, Brown CC, Haines DC, Phang JM.

PMID: 9230186

9. pdf-available Nature. 2002 Jul 18;418(6895):344-8.

Calorie restriction extends Saccharomyces cerevisiae lifespan by increasing

respiration.

Lin SJ, Kaeberlein M, Andalis AA, Sturtz LA, Defossez PA, Culotta VC, Fink GR,

Guarente L.

PMID: 12124627

10. pdf-available Am J Clin Nutr. 1997 Oct;66(4):890-903.

Longevity in obese and lean male and female rats of the Zucker strain:

prevention of

hyperphagia.

PR, Stern JS, Horwitz BA, RE Jr, Greene SF.

PMID: 9322565

11. Proc Natl Acad Sci U S A. 1998 Oct 27;95(22):13091-6.

The genetics of caloric restriction in Caenorhabditis elegans.

Lakowski B, Hekimi S.

PMID: 9789046

http://www.pnas.org.qe2a-proxy.mun.ca/cgi/content/abstract/95/22/13091?ijkey=739\

cfd5b03bb2b9a1c2cd1348cb71775e3941425 & keytype2=tf_ipsecsha

12. Clancy, D. J., Gems, D., Hafen, E., Leevers, S. J. & Partridge, L. (2002)

Dietary restriction in long-lived dwarf flies.

Science 296:319-325.

http://www.sciencemag.org.qe2a-proxy.mun.ca/cgi/content/full/296/5566/319?ijkey=\

8c223ef1f220f44820d8f1ee42294f5dfbff65e9 & keytype2=tf_ipsecsha

13. Proc Natl Acad Sci U S A. 1984 Mar;81(6):1835-8.

Effects of food restriction on aging: separation of food intake and adiposity.

on DE, Archer JR, Astle CM.

PMID: 6608731

http://www.pnas.org.qe2a-proxy.mun.ca/cgi/reprint/81/6/1835

14. Proc Natl Acad Sci U S A. 1984 Mar;81(6):1835-8.

Effects of food restriction on aging: separation of food intake and adiposity.

on DE, Archer JR, Astle CM.

PMID: 6608731

15. J Nutr. 1986 Apr;116(4):641-54.

The retardation of aging in mice by dietary restriction: longevity, cancer,

immunity

and lifetime energy intake.

Weindruch R, Walford RL, Fligiel S, Guthrie D.

PMID: 3958810

16. J Gerontol. 1982 Mar;37(2):130-41.

Life span study of SPF Fischer 344 male rats fed ad libitum or restricted diets:

longevity, growth, lean body mass and disease.

Yu BP, Masoro EJ, Murata I, Bertrand HA, Lynd FT.

PMID: 7056998

17. J Am Vet Med Assoc. 2002 May 1;220(9):1315-20.

Effects of diet restriction on life span and age-related changes in dogs.

Kealy RD, Lawler DF, Ballam JM, Mantz SL, Biery DN, Greeley EH, Lust G, Segre M,

GK, Stowe HD.

PMID: 11991408

18. J Anim Sci. 1972 Jun;34(6):1067-74. No abstract available

Lifetime effects of winter supplemental feed level and age at first parturition

on

range beef cows.

Pinney DO, s DF, Pope LS.

PMID: 5027302

Further information is:

When considering modeling energy balance in cancer models, it is helpful to

consider

the factors that contribute to an organism’s overall energy balance. Energy

intake

is one part of the equation, and its components include the total amount of

energy

consumed as well as the source of that energy in the diet and the pattern of

food

consumption. In contrast, physical activity, growth, energy storage, routine

metabolism, and thermoregulation are on the output side of the energy balance

equation (6).

In terms of cancer, the energy intake side of the equation has been best

studied,

particularly comparing ad libitum (unlimited) access to food with calorie

restriction (CR)3 in the range of a 20–40% reduction in calorie intake relative

to

ad libitum food consumption (7). As shown in Figure 1, CR has been shown to

increase

longevity in multiple species and exert inhibitory effects against a variety of

spontaneous neoplasias in several experimental model systems (8–18). CR also

suppresses the carcinogenic action of several classes of chemicals in rodents,

including polycyclic aromatic hydrocarbons, e.g., benzo(a)pyrene, and

dimethylbenz(a)anthracene (DMBA); alkylating and methylating agents, e.g.,

diethylnitrosamine; and aromatic amines, e.g., p-cresidine (19). In addition, CR

inhibits several forms of radiation-induced cancers (19). Thus, the inhibitory

action of CR on carcinogenesis is effective in several species, for a variety of

tumor types, and for both spontaneous tumors and chemically induced neoplasias.

Despite the reproducibility and breadth of the beneficial anti-aging and

anti-cancer

effects of CR, the underlying biological mechanisms of CR are not well

understood.

Furthermore, the lessons learned from CR research have not yet been effectively

translated into strategies for human health promotion or disease prevention.

The recent development of genetically engineered mouse strains with

cancer-related

genes overexpressed or inactivated provides investigators with powerful tools

for

studying carcinogenesis and for testing preventive strategies that can offset

increased genetic susceptibility to cancer as a result of specific genetic

lesions

in humans (20). Our work has focused on preventing cancer by dietary

interventions,

particularly obesity prevention/energy balance modulation, in mice deficient in

the

p53 tumor suppressor gene, the most frequently altered gene in human cancer. We

describe here the results from these studies and discuss future directions for

mechanism-based cancer prevention research using relevant animal models.

p53-Deficient mice

Mutation of the p53 tumor suppressor gene is the most frequently observed

genetic

lesion in human cancer; over 50% of all human tumors examined to date have

identifiable p53 gene point mutations or deletions (21). Donehower et al. (22)

first

reported in 1992 that homozygous p53-knockout (p53–/–) mice are viable but

highly

susceptible to spontaneous tumorigenesis (particularly lymphomas) at an early

age.

p53–/– mice have been useful tools for studying the role of p53 in

carcinogenesis.

For example, in response to a DMBA-induced skin carcinogenesis protocol, p53–/–

mice, relative to wild-type (p53+/+) mice, show no difference in benign

papilloma

formation but display greatly accelerated progression to malignant carcinomas

(23).

Furthermore, the carcinomas formed in the p53–/– mice show higher indices of

malignancy as measured by histopathology, further confirming the importance of

p53

loss in acceleration of tumor progression. p53-deficient mice also provide an

attractive and relevant tumorigenesis model for studying cancer prevention

strategies given the frequency of p53 mutations in human tumors and the rapidity

with which spontaneous tumors develop in these mice.

Cancer prevention studies in p53-null (p53–/–) mice

We have evaluated the ability of several dietary and chemopreventive

interventions

to offset the increased susceptibility of p53–/– mice to spontaneous

tumorigenesis

(8,24–26). Given its potency in a variety of models and tissue types, we chose

CR as

our initial proof of principle that a dietary intervention could influence

tumorigenesis in mice predestined to develop tumors due to a lack of the p53

tumor

suppressor. In p53–/– mice, CR (60% of the control group’s energy intake,

achieved

by reducing carbohydrate calories) increases the latency of spontaneous tumor

development (mostly lymphomas) 75% and significantly slows thymocyte and

splenocyte

cell cycle traverse (24). The time to tumor onset in these mice is largely

p53-dependent, with the majority of p53–/– mice developing and dying from

spontaneous tumors by approximately 6 months of age compared to nearly 2 years

for

p53+/+ mice. However, the highly statistically-significant tumor-delaying effect

of

CR, relative to ad libitum consumption, is similar in both p53–/– and wild-type

(p53+/+) mice, indicating the mechanisms underlying CR may be p53-independent

(8).

We have also found that several nutritional and chemopreventive agents could

influence tumorigenesis in this model. Perhaps the most striking effect was with

the

chemopreventive steroid dehydroepiandrosterone (DHEA; 0.3% in the diet), which

decreases adiposity and significantly delays spontaneous tumorigenesis in p53–/–

mice and, in particular, nearly eliminates lymphoma development (25).

Furthermore,

the DHEA analogue 16--fluoro-5-androsten-17-one (fluasterone; 0.15% in the diet)

also decreases adiposity and suppresses spontaneous lymphoma development and

lengthens survival in p53–/– mice (26). The anti-lymphomic effects of these

chemopreventive steroids are strongly associated with decreased body weight as

well

as with delayed thymocyte maturation and increased apoptotic rates of

premalignant

thymocytes [(26,28,29); Kim, Hursting, and Perkins, unpublished results]. Taken

together, these findings clearly demonstrate that the increased susceptibility

to

cancer as a result of a genetic lesion, such as loss of p53 tumor suppressor

function, can be offset, at least in part, by preventive approaches.

p53–/– mice have also been useful for elucidating the mechanisms of action

underlying the tumor-inhibitory effects of CR and the chemopreventive steroids.

For

example, the anti-tumor effect of DHEA (or its fluorinated analogue fluasterone)

in

p53–/– mice is independent of its effects on quantity of food intake or on

nucleotide pool levels (26), as had previously been suggested (27). Wang et al.

showed that both CR and DHEA decrease thymocyte proliferative rates (28).

Poetschke

et al. (29) showed that calorie restriction, DHEA, and fluasterone each slow

thymocyte cell cycle progression, partially blocks thymocyte maturation, and

induce

apoptosis in immature thymocytes, the subpopulation of thymocytes from which

lymphomas arise in p53–/– mice. However, the apoptosis-inducing effects of the

chemopreventive steroids appear to be mediated by decreased Bcl-2 gene

expression,

while the effects of CR on apoptosis are independent of the Bcl-2/ Bax apoptotic

regulatory pathway. On the other hand, CR (but not the steroids) significantly

reduces circulating IGF-1 levels (30), which as suggested by Dunn et al. (31)

may be

responsible for the apoptotic-inducing effects of CR. Both CR and the

chemopreventive steroids also decrease serum leptin levels (Hursting et al.,

unpublished results). Leptin, the so-called fat hormone, has been shown to act

as a

pro-inflammatory cytokine (32), a pro-angiogenic factor (33), and also an

apoptotic

regulator in certain cell types (34), so this reduction in leptin levels may

also

contribute to the effects of CR. In addition, Mei et al. showed that CR, DHEA,

and

fluasterone each suppress nitric oxide levels and downregulate nitric oxide

synthetase expression (35). The roles of IGF-1, leptin and nitric oxide and

other

inflammatory components in the anti-cancer effects of CR in p53–/– mice are

currently being further characterized.

Cancer prevention studies in p53+/– mice

Heterozygous p53-knockout (p53+/–) mice, with only one p53 allele inactivated,

have

some analogy to humans susceptible to heritable forms of cancer due to decreased

p53

gene dosage, such as individuals with Li-Fraumeni Syndrome (36). The spontaneous

tumors that most frequently occur in p53+/– mice (hematopoietic neoplasias and

osteosarcomas) are similarly observed in humans with Li-Fraumeni Syndrome. The

incidence rates of the 2 most common epithelial tumors observed in Li-Fraumeni

patients (lung tumors in males and breast tumors in females) vary depending on

the

background strain of the p53-deficient mice (37,38). Tumor latency in p53+/–

mice

(median survival 18 mo) is reduced relative to p53+/+ mice (median survival 26

mo),

although is much longer than for p53–/– mice (median survival 6 mo). CR and a

one-day per week fast both significantly delay spontaneous tumor development

(mostly

lymphomas and various sarcomas) in male p53+/– mice, even when interventions are

begun in adulthood (30).

While p53+/– mice have low rates of spontaneous tumorigenesis for up to 12 mo of

age, they do display increased susceptibility to chemically induced tumor

development relative to wild-type mice. p-Cresidine-induced bladder tumors (31),

dimethylnitrosamine-induced liver tumors (37), nitrosomethylurea-induced

lymphomas

(S. Perkins and S. Hursting, unpublished results), and radiation-induced

lymphomas

and sarcomas (39) all appear significantly earlier in p53+/– mice than in

similarly-treated p53+/+ mice. As mentioned previously, malignant progression of

DMBA-induced skin papillomas also occurs much faster in p53+/– mice than in

p53+/+

mice (23). These findings suggest that p53+/– mice exhibit increased sensitivity

to

several classes of mutagenic carcinogens when compared to p53+/+ mice, and

appear to

be susceptible to at least some low-dose, chronic carcinogen regimens that more

closely mimic human exposures.

Using the p-cresidine-induced bladder tumor model in male p53+/– mice, we showed

that CR (started after tumors had formed) suppresses bladder tumor progression

(31).

Furthermore, IGF-1 appears to mediate the CR response, as restoration of serum

IGF-1

levels in CR mice via osmotic pump infusion reverses the CR effect. We had

previously reported (40) a similar finding of a mediating role for IGF-1 in the

anti-cancer effects of CR using a Fischer rat leukemia model. As demonstrated by

these studies, genetically engineered mice, such as p53-deficient mice, have

tremendous potential for developing models facilitating the study of

gene-environment interactions relevant to human cancer prevention.

Experimental evidence for the role of IGF-1 in cancer

The possible involvement of IGF-1 in cancer was first observed in in vitro

studies,

which consistently showed that IGF-1 enhances the growth of a variety of cancer

cell

lines (41). These include prostate, bladder, breast, lung, colon, stomach,

esophagus, liver, pancreas, kidney, thyroid, brain, ovarian, and cervical and

endometrial cancer cell lines (41–43). IGF-1 acts directly on cells via the

IGF-1R,

which is overexpressed in many tumors, or indirectly through its action with

other

cancer-related molecules, including p53. For example, IGF-1 and the p53 tumor

suppressor appear to function together in a regulatory network. p53 regulates

the

expression of IGFBP-3 (44) and IGF-1-induced mitogenesis is associated with

phosphorylation and translocation of the p53 protein from the nucleus to the

cytoplasm (45)

A markedly increased average and maximal life span and decreased susceptibility

to

cancer is also observed in several strains of mutant or genetically modified

mice

that suffer defects in the production of growth hormone or IGF-1 or in

responsiveness to growth hormone (and hence express significantly lower levels

of

circulating IGF-1). The " little " mouse, which is defective in its response to

hypothalamic growth hormone-releasing hormone, lives 20–25% longer than

wild-type

mice (46). Laron mice, with a disruption in the growth hormone receptor/binding

protein gene, have increased circulating levels of growth hormone but greatly

reduced serum IGF-1 levels and also live 38–55% longer than wild-type mice (47).

Mice with primary deficiencies in growth hormone, prolactin, and thyrotropin,

caused

by failure of the pituitary to differentiate during fetal development, live 40

to

64% longer than wild-type mice. These latter examples include the Snell and

dwarf mice, which have a point mutation in the homeotic transcription factor

Pit1

(48), and the Ames dwarf mouse, which fails to express Pit1 because of an

inactivating point mutation in the Prop1 transcription factor (49). As seen with

CR,

these mutations appear to reduce the onset and/or rate of aging and

age-associated

cancers. In contrast, tissue-specific overexpression of IGF-1 via the keratin 5

promoter results in increased spontaneous tumor development (50) and increased

susceptibility to carcinogens, including p-cresidine (Hursting et al.,

unpublished

results).

Epidemiological evidence of a role for IGF-1 in human cancer

There is an abundance of epidemiological evidence that supports the hypothesis

that

IGF-1 may be involved in human cancer. In a case-control study nested within the

Nurses Health Study cohort, Hankinson et al. (51) found that elevated serum

IGF-1

levels are associated with an increased risk of developing breast cancer in

premenopausal women [relative risk (RR): 2.3; CI: 1.1–52] but not in

postmenopausal

women. Yu et al. also found associations between IGF-1 levels and premenopausal

breast cancer risk in Chinese women (52). In contrast, Kaaks et al. (53) found

no

association between IGF-1 levels and premenopausal breast cancer risk in Swedish

women but suggested a possible association with postmenopausal breast cancer

risk.

Chan et al. (54) in the Physicians’ Health Study cohort found that plasma IGF-1

levels were associated with a higher risk of developing a prostate cancer (RR:

4.3;

CI: 1.8–10.6). Yu et al. (55) reported that IGF-1, but not IGF-2 or IGFBP-3

levels,

was associated with lung cancer. Ma et al. (56) found that both elevated levels

of

IGF-1 and decreased levels of IGFBP-3 were associated with an increased risk of

developing colon cancer in men in the Physicians’ Health Study. High plasma

levels

of IGF-1 and low levels of IGF binding protein-3 have been associated with an

increased risk of bladder cancer (57), while reduced risk of childhood leukemia

in

association with higher IGFBP-3 levels has also been reported (58). The

epidemiological association between IGF-1 and IGFBP levels and the risk of

various

cancers certainly requires more investigation, including additional prospective

studies to better establish the temporal nature of any associations. However,

when

considered together, the multiple human studies reported to date suggest that

components of the IGF-1 system are risk factors important in the development of

several human cancers.

Summary and future directions

Carcinogen-induced models of cancer in rodents have been crucial to advancing

our

understanding of the neoplastic process, and recent progress in the fields of

toxicology, pathology, and molecular carcinogenesis has revealed multiple

targets

for the nutritional modulation and chemoprevention of cancer. We must now

capitalize

on the availability of new tools such as genetically engineered mice, gene

expression microarrays, and proteomics to identify additional modulatable

targets

and make important progress towards one of the major goals in contemporary

cancer

research: the development of effective mechanism-based strategies for preventing

human cancer. In this review, examples of cancer prevention studies that have

utilized p53-deficient mouse models were discussed. Taken together, these

examples

clearly indicate that mice with specific (and human-like) genetic

susceptibilities

for cancer provide powerful new tools for testing interventions that may inhibit

the

process of carcinogenesis in humans. Further development of relevant animal

models

for prevention studies and the incorporation of new technologies (such as

microarrays and proteomics) into these studies are approaches that we are taking

to

accelerate the pace of mechanism-based cancer prevention research. For example,

to

further study diet-p53 interactions in mammary carcinogenesis, we have been

characterizing a rapid and spontaneous p53-deficient mouse mammary tumor model

developed by crossing p53+/– mice with MMTV-Wnt-1 transgenic mice (59). In these

mice CR, a one day/wk fast, the synthetic retinoid fenretinide, tamoxifen, and

the

chemopreventive steroid fluasterone each delay spontaneous mammary tumor

development

(Hursting et al., unpublished results). Furthermore, p53 gene dosage impacts the

magnitude of these preventive effects.

Regarding studies of energy balance and cancer, which are essential given the

impact

of obesity on cancer development and the paucity of mechanistic data on this

association, we are in the process of comparing and combining CR and exercise in

our

p53-deficient mouse models, as well as other tumor models. This includes APCmin

mice, which spontaneously develop preneoplastic intestinal polyps that can be

suppressed by CR and exercise (60,61). We are also further investigating the

role of

IGF-1, other hormones, and body composition in the energy balance and cancer

relationship. For example, to elucidate the molecular response underlying the

anticancer effects of CR, and to determine which of the CR- responsive genes are

IGF-1–dependent, we are using a strategy employing oligonucleotide microarrays.

Preliminary analyses of hepatic RNA from a 4-wk study in wild-type (C57 BL/6)

mice

fed ad libitum or 20, 30, or 40% CR and receiving either a placebo pellet or an

IGF-1 pellet implanted subcutaneously suggest that CR induces changes in the

expression of multiple genes associated with phase 1 and phase 2 xenobiotic

metabolism, steroid hormone metabolism, cell cycle/DNA repair, and the IGF-1

pathway. Our approach will continue to include the development and use of

relevant

animal models as well as the adoption of new technologies to accelerate the

discovery and characterization of effective cancer preventive interventions and

their translation to human populations.

FOOTNOTES

Presented at the 6th Postgraduate Course on Nutrition entitled " Nutrition and

Gene

Regulation " Symposium at Harvard Medical School, Boston, MA, March 13–14, 2003.

This

symposium was supported by Conrad Taff Nutrition Educational Fund, ConAgra

Foods,

GlaxoKline Consumer Healthcare, McNeil Nutritionals, Nestle Nutrition

Institute, The Peanut Institute, Procter & Gamble Company Nutrition Science

Institute, Ross Products Division–Abbott Laboratories, and Slim Fast Foods

Company. ...

Al Pater, PhD; email: old542000@...

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