Diet and the prevention of cancer

circITGA7 Functions as an Oncogene by Sponging miR-198 and Upregulating FGFR1 Expression in Thyroid Cancer

BACKGROUND

Emerging evidence has indicated that circular RNAs (circRNAs), recognized as functional noncoding transcripts in eukaryotic cells, may be involved in regulating many physiological or pathological processes. However, the regulation and function of circular RNA circITGA7 in thyroid cancer (TC) remains unknown.

METHODS

In this study, we found that circITGA7 is upregulated in TC cell lines. We then performed functional analyses in the cell lines to support clinical findings. Mechanistically, we demonstrated that circITGA7 can directly bind to miR-198 and reduce the inhibition effect of miR-198 on target FGFR1 expression.

RESULTS

We reported an upregulation of circITGA7 in patients with TC. Silencing of circITGA7 inhibits metastasis and proliferation of TC cell lines in vitro. In addition, in the TC cell lines, the knockdown of circITGA7 or overexpression of miR-198 significantly suppressed FGFR1 levels. Mechanistically, we found that circITGA7 acts as miR-198 competitive endogenous RNA (ceRNA) to regulate FGFR1 expression.

CONCLUSIONS

In summary, circRNA circITGA7 may play a regulatory role in TC and may be a potential marker for TC diagnosis or progression.

Chemomodulatory Effect of Trigonella foenum graecum (L.) Seed Extract on Two Stage Mouse Skin Carcinogenesis

Cancer is not a single disease but a group of complex genetic diseases of aged cells. Chemoprevention of cancer is the attempt to use natural and synthetic compounds to intervene in the early stages of cancer, before invasive disease begins. Consuming a diet rich in plant foods can provide a milieu of phytochemicals and non-nutritive plant substances that possess health-protective effects. Some phytochemicals derived in spices and herbs as well as other plants possess substantial cancer preventive properties. Thus the cancer chemo preventive potential of naturally occurring phytochemicals is of great interest because of their preventive role and as they are not perceived as "medicine". During the course of present study Trigonella foenum graecum (L.) seed- TFGS (commonly called fenugreek) extract was given at pre-initiational, post-initiational, promotional and throughout the experiment along with 7,12-dimethylbenz [a] anthracene DMBA and 12-O-tetradecanoylphorbol-13-acetate TPA treatment in Swiss albino mice. A significant reduction of papillomas in DMBA + TPA + TFGS (400 mg/kg. body wt.) treated group was found to be effective in decreasing the rate of tumor incidence in comparison to control. Furthermore, cumulative number of papillomas, tumor yield and tumor burden were also found to be reduced. The TFGS extract treatment before DMBA and TPA application (i.e. Pre initiation) were more effective than that of treatment during, and /or after DMBA treatment, however TFGS extract treatment was most effective when treated throughout all the stages of tumorigenesis. The TFGS treatment also showed a modulatory influence on mouse hepatic antioxidant defense system (GSH and LPO level).

Assessment of information to substantiate a health claim on the prevention of prostate cancer by lignans

Lignans and their in vivo metabolites, especially enterolactone (ENL), have attracted substantial interest as potential chemopreventive agents for prostate cancer. Preclinical and clinical interventions performed with lignan-rich flaxseed that use surrogate biomarkers as endpoints suggest that lignans may attenuate prostate carcinogenesis in individuals with increased risk or with diagnosed cancer. No unequivocal prostate cancer risk reduction has been found for lignans in epidemiological studies, suggesting that lignan concentrations found in populations consuming a regular non-supplemented diet are not chemopreventive in prostate cancer. Presumably, the main obstacles in assessing the efficacy of food lignans is limited knowledge of the serum and tissue lignan concentrations required for the putative prevention. Further clinical studies performed with the purified compounds are required to substantiate a health claim.

Does biliopancreatic diversion carry increased risk for colorectal cancer? A cohort study

BACKGROUND

Because of the rearrangement of the gastrointestinal tract, biliopancreatic diversion (BPD) could lead to an increased risk of colorectal cancer caused by possible carcinogenetic action of the unabsorbed food and bile acid on colonic mucosa.

METHODS

The incidence of colorectal cancer in 1,898 obese subjects submitted to BPD from May 76 to July 2002 with a minimum follow-up of 5 years was retrospectively evaluated.

RESULTS

Among 28,811 person-years, seven cases of colorectal cancer were detected, for an overall incidence of 29.4 per 100,000, which is not different from that observed in the general Italian population, and lower than that reported for obese and type 2 diabetes patients. Logistic regression model suggests that occurrence of colorectal cancer is positively related to the time elapsed from BPD.

CONCLUSION

This study indicates that BPD does not carry any increased risk for colorectal cancer. The complete postoperative restoration of insulin sensibility could exert a valuable protective action.

Strategies for cancer prevention: the role of diet

Linkages between diet habits and cancer risk have surfaced from a multitude of epidemiological and preclinical studies. Collectively these studies provide rather compelling evidence that dietary components modify the incidence and biological behavior of tumors. While the risk of breast, prostate, colon, lung and liver cancers are frequently associated with dietary patterns, inconsistencies are not uncommon. These inconsistencies likely reflect the multi-factorial and complex nature of cancer and the specificity that individual dietary constituents have in modifying cancer related genetic pathways. The complexity of defining the role of diet is underscored by the numerous and diverse essential and non-essential components that may alter one or more phases of the cancer process. The explosive increase in the recognition of genes and pathways for regulating cell growth and development, and evaluating the response to hormones and other chemicals synthesized by the body, offers exciting opportunities for unraveling the molecular targets by which dietary components influence cancer prevention. It is recognized that all cells have unique ‘signatures’ that are characterized by active and inactive genes and cellular products. It is certainly plausible that bridging knowledge about these unique cellular characteristics with the molecular targets for nutrients can be used to assist in optimizing nutrition and minimizing cancer risk.

Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances

Although the avocado is known as a rich source of monounsaturated fatty acids, there has been far less attention given to its content of other bioactive substances including carotenoids, which might contribute to cancer preventive properties similar to those attributed to other fruits and vegetables. The yellow-green color of the avocado prompted us to study the carotenoid content of this fruit using established methods in our laboratory. The California Hass avocado (Persea americana Mill.) was selected for study, because it is the most commonly consumed variety in the southwest United States. These avocados were found to contain the highest content of lutein among commonly eaten fruits as well as measurable amounts of related carotenoids (zeaxanthin, alpha-carotene, and beta-carotene). Lutein accounted for 70% of the measured carotenoids, and the avocado also contained significant quantities of vitamin E. An acetone extract of avocado containing these carotenoids and tocopherols was shown to inhibit the growth of both androgen-dependent (LNCaP) and androgen-independent (PC-3) prostate cancer cell lines in vitro. Incubation of PC-3 cells with the avocado extract led to G(2)/M cell cycle arrest accompanied by an increase in p27 protein expression. Lutein alone did not reproduce the effects of the avocado extract on cancer cell proliferation. In common with other colorful fruits and vegetables, the avocado contains numerous bioactive carotenoids. Because the avocado also contains a significant amount of monounsaturated fat, these bioactive carotenoids are likely to be absorbed into the bloodstream, where in combination with other diet-derived phytochemicals they may contribute to the significant cancer risk reduction associated with a diet of fruits and vegetables.

A carcinogenic western diet does not induce somatic mutations in various target tissues of transgenic C56BL/6 mice

Although the importance of diet in human cancer is clear, most dietary studies of carcinogenesis in laboratory rodents have involved the use of large doses of a carcinogen, which is not comparable to the human situation. The use of carcinogens has been necessary because laboratory rodents have extremely low spontaneous rates of colon cancer. Newmark et al. (2001) showed, however, that a radical dietary manipulation sufficed to induce high rates of colon cancer in C57BL/6 mice. Here we report an investigation into whether or not this dietary manipulation acts by altering somatic mutation rates. We used the transgenic lambda cII locus of F1 pups (C57BL/6 x Big Blue with the same C57BL/6 genetic background. The same diet (ND), high in fat, and low in calcium, vitamin D, folic acid, choline, and fibre, that was used by Newmark et al. (2001) was fed ad libitum to dams during pregnancy and lactation in order to examine its effect on mutagenesis in development and growth. There was no significant difference in mutant frequency in the small intestine (P = 0.82), or bone marrow (P = 0.95) of pups fed a ND versus the control diet. To investigate the effect of a ND during adulthood, 6-week-old F1 pups were fed a ND ad libitum for 6, 12 and 19 weeks. There was no significant difference in mutant frequency in the small intestine (P = 0.66) or colon (P = 0.49) at the cII locus with no significant difference in body weight. These results indicate that Western diet-induced carcinogenesis is not mediated by alterations in mutation rate and thus may act at the promotion rather than at the initiation stage of carcinogenesis.

Vitamin D and colon carcinogenesis

Colorectal cancer is the third most commonly occurring cancer in the United States and accounts for approximately 11% of cancer deaths. Many epidemiological studies have shown an association between dietary factors, including calcium and vitamin D, and the incidence of colon cancer. Recently the Calcium Polyp Prevention Study demonstrated that calcium supplementation can reduce the recurrence of colon polyps, but the effect depends on serum vitamin D levels. We used the Apc(min) mouse model of intestinal cancer to investigate the effects of vitamin D treatment and calcium intake independently on polyp formation. We found that 1,25-dihydroxycholecaliferol was potent in inhibiting tumor load; however, the dose used to achieve this antiproliferative effect led to deleterious effects on serum calcium homeostasis. These effects were minimized by use of a synthetic analogue with reduced toxicity. Additionally, we tested the effect of a modified-calcium diet in Apc(min) mice but did not find a protective effect, perhaps because of a reduction in circulating levels of 25-hydroxycholecaliferol with increasing levels of dietary calcium. A number of other studies that use rodent models with vitamin D supplementation or deficiency illustrate the efficacy of vitamin D in colon cancer prevention. The mechanisms of direct action of vitamin D on colonic epithelium include regulation of growth factor and cytokine synthesis and signaling, as well as modulation of the cell cycle, apoptosis, and differentiation. Because of the apparent synergistic effect of vitamin D and calcium, cosupplementation of both nutrients in cancer prevention programs may be advised.

Sodium copper chlorophyllin: in vitro digestive stability and accumulation by Caco-2 human intestinal cells

Sodium copper chlorophyllin (SCC), a mixture of water-soluble chlorophyll derivatives, is used as both a food colorant and a common dietary supplement. Although the potential antimutagenic and antioxidant properties of this commercial preparation have been demonstrated, limited information is available on its digestion and absorption by humans. Stability of SCC was examined during simulated gastric and small intestinal digestion. Three preparations were subjected to in vitro digestion: SCC in water, SCC in water + 10% corn oil, and SCC in applesauce. SCC components from raw material preparations and in digested samples were analyzed by C(18) HPLC with photodiode array detection. Cu(II)chlorin e(4), the major chlorin component of SCC, was relatively stable during simulated digestion. In contrast, greater than 90% of Cu(II)chlorin e(6) was degraded to undetermined products during digestion. Recovery of Cu(II)chlorin e(6) after digestion was increased by incorporation of SCC into applesauce, suggesting a protective role of the inclusion matrix for stabilization of labile SCC components. Accumulation of SCC derivatives was investigated by using differentiated cultures of the TC7 clone of the Caco-2 human intestinal cell line. Cellular accumulation from media containing 0.5 to 60 ppm SCC was linear with intracellular content ranging between 0.2 and 29.6 microg of total SCC per mg of cellular protein. Uptake of SCC by Caco-2 cells was significantly (p < 0.01) lower in cultures incubated at 4 degrees C than in those incubated at 37 degrees C. Although intracellular SCC was transported into both apical and basolateral compartments when Caco-2 cells were grown on inserts, apical efflux was significantly greater (p < 0.01) than basolateral efflux. Stability of Cu(II)chlorin e(4) during in vitro digestion and effective uptake by Caco-2 enterocyte-like cells support the likelihood that a portion of this SCC component or its metabolites is absorbed from the human intestine.

Diet, natural products and cancer chemoprevention

There is considerable scientific evidence to suggest that nutritive and nonnutritive plant-based dietary factors can inhibit the process of carcinogenesis effectively. Cancer chemoprevention involves pharmacologic intervention with synthetic or naturally occurring chemicals to prevent, inhibit or reverse carcinogenesis or prevent the development of invasive cancer. In light of the considerable effort that has been expended by scientists from the academic, governmental and private sectors in identifying, characterizing and utilizing potential cancer chemopreventive agents, it is reasonable to inquire about the progress that has been made to date and the promise that this field holds in the fight against cancer. The symposium entitled Diet, Natural Products and Cancer Chemoprevention: Progress and Promise was therefore organized at Experimental Biology 99 by the American Society for Nutritional Sciences to address in part these two issues. Progress in the development of cancer chemopreventive agents, examples of current clinical and experimental research of particular relevance to cancer prevention and the promise of chemoprevention in effectively contributing to the conquest of cancer were highlighted.