Mechanisms of Cancer Cachexia

Nutritional aspects of cancer-related fatigue

Fatigue, which may well be the most common experience of patients with cancer, remains underappreciated by health care professionals. Perhaps one reason is that because of its complexity and many components, fatigue is not completely understood. Knowledge of fatigue models, such as the integrated Fatigue Model of Piper, can help dietitians identify potential causes of fatigue such as activity-rest patterns, and identification can lead dietitians to early intervention. Understanding cancer treatment factors, such as nausea and decreased participation in activities of daily living, that are believed to play a part in fatigue form another level on which dietitians can provide intervention. Through intervention, dietitians, working with patients and other members of the multidisciplinary team, may increase the understanding and appreciation of fatigue as well as provide relief from it. Efforts to maintain nutritional status can decrease or prevent some of the fatigue associated with cancer and its treatment. Therefore, the goal of clinical dietitians who work with a fatigued patient with cancer is to use nutrition management to minimize therapeutic side effects and maximize the patient's nutritional parameters.

Involvement of prostaglandins in cachexia induced by T-cell leukemia in the rat

We have previously demonstrated that experimentally induced T-cell leukemia in the rat results in a rapid and severe cachexia. This weight loss is largely due to a reduction in food intake, but is also accompanied by inappropriately high rates of energy expenditure. Increases in resting oxygen consumption (VO2) of 25% to 35% above the levels of pair-fed animals were observed over the period of weight loss. The present study investigated the possible involvement of prostaglandins in the cachexia induced by T-cell leukemia in the rat. Acute systemic injection of the cyclo-oxygenase inhibitors (indomethacin 1 mg/kg or flurbiprofen 1 mg/kg intraperitoneally [IP]) significantly reduced (by 14% and 10%, respectively) the increase in metabolic rate and also reversed the elevated body temperature of leukemic animals. Intracerebroventricular (ICV) injection of indomethacin (0.2 mg/kg) had only modest effects on the increase in temperature or hypermetabolism of leukemic animals. Long-term daily injection of indomethacin or flurbiprofen (1 mg/kg/d IP) had no significant effect on food intake or body weight of leukemic animals, and neither treatment significantly affected disease status. Indomethacin significantly reduced the decline in epididymal fat pad weight of leukemic animals. These data indicate that prostaglandins, produced peripherally, are involved in the acute hypermetabolism associated with T-cell leukemia, but have little or no effect on the hypophagia or body weight loss of leukemic rats.

Molecular cloning of a gene encoding a new type of metalloproteinase-disintegrin family protein with thrombospondin motifs as an inflammation associated gene

A cellular disintegrin and metalloproteinase (ADAM) is a new family of genes with structural homology to the snake venom metalloproteinases and disintegrins. We screened genes which were selectively expressed in the cachexigenic colon 26 adenocarcinoma subline in vivo. It was found that one novel cDNA clone, identified as a cachexigenic tumor selective gene, encodes a cysteine-rich protein which shows a sequence similarity to that of both the snake venom metalloproteinases and thrombospondins. We named this cDNA clone A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-1). ADAMTS1 consists of six domains, 1) a pro- and 2) a metalloproteinase, 3) a disintegrin-like, 4) a thrombospondin (TSP) homologous domain containing TSP type I motif, 5) a spacer region, and 6) COOH-terminal TSP submotifs. Unlike other ADAMs, ADAMTS-1 does not possess a transmembrane domain and is a putative secretory protein. Therefore, ADAMTS-1 is a new type of ADAM family protein with TSP type I motifs. We demonstrated that the TSP homologous domain containing the TSP type I motif of ADAMTS-1 is functional for binding to heparin. ADAMTS-1 mRNA could be induced by stimulating colon 26 cells with an inflammatory cytokine, interleukin-1, in vitro. Moreover, intravenous administration of lipopolysaccharide in mice selectively induced ADAMTS-1 mRNA in kidney and heart. These data suggest that ADAM-TS-1 may be a gene whose expression is associated with various inflammatory processes as well as development of cancer cachexia.

Cracking the riddle of cancer anorexia

During tumor growth, anorexia and reduced food intake are among the major causes leading to malnutrition and eventually cachexia, which negatively affect patients' outcome. Consistent evidence from our laboratories in rats and humans indicates a key role for ventromedial hypothalamic (VMH) serotonergic system in the development of cancer anorexia. Thus, we postulated that during cancer, increased plasma tryptophan levels (the precursor of serotonin) lead to increased cerebrospinal fluid tryptophan concentrations and increased VMH serotonin synthesis, which then mediates the occurrence of anorexia. However, recent data strongly suggest that factors other than tryptophan supplied to the central nervous system might be involved in the pathogenesis of reduced food intake during tumor growth. Particularly, a significant role appears to be played by interleukin-1 (IL-1). We recently showed that IL-1 infusion in normal rats causes changes in food intake and its determinants, meal number and meal size, similar to those characterizing cancer anorexia, thus supporting the involvement of this cytokine in the development of anorexia. Interestingly, IL-1 and the VMH serotonergic system appear to be closely linked: peripherally infused IL-1 increases brain tryptophan and serotonin concentrations, while intracerebrally infused IL-1 increases neuronal firing rate and serotonin release. We therefore hypothesize that during tumor growth, increased production/secretion of IL-1 occurs, which facilitates the tryptophan supply to the brain. IL-1 can then also act on the VHM itself, where IL-1 receptors exist, to increase its neuronal activity and serotonin release. In other words, we believe that centrally acting IL-1 increases hypothalamic neuronal firing rate and serotonin release, while peripherally acting IL-1 is critical in supplying the hypothalamus with the precursor, tryptophan, in order to maintain the high rate of serotonin synthesis. Also, additional factors recently proposed as mediators of anorexia (including neuropeptide Y and nitric oxide) appear to be part of the hypothesized pathogenic mechanism.

Are cytokines possible mediators of cancer cachexia?

The possible role of cytokines in the development of cancer cachexia was reviewed from the literature. Tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, IL-6, interferon (IFN)-gamma and leukemia inhibitory factor (LIF) can elicit many but not all host changes seen in cancer cachexia, including loss of appetite, loss of body weight, and the induction of acute-phase protein synthesis. However, these cytokines are not always demonstrated in the circulation of the cancer patients. The inability to detect circulating cytokines may be due to their low rate of production, their short half-life and rapid clearance from plasma, or their mode of action (autocrine or paracrine). Different cytokines are induced to stimulate the same response. This is very different from hormonal regulation, where a hormone acts on a cell directly through a specific receptor without depending on other mediators. Specific antibodies including anti-IFN-gamma, anti-TNF and anti-IL-6 antibodies, as well as the cyclooxygenase inhibitor indomethacin, have been used to reverse cancer cachexia. Overlapping physiologic activities make it unlikely that a single substance is the sole cause of cancer cachexia. It is hoped that further investigation on other cytokines and their possible relationships with hormones will help to clarify the mechanisms of cancer cachexia in the near future.

The lack of an effect by insulin or insulin-like growth factor-1 in attenuating colon-2-mediated cancer cachexia

In several studies, the anabolic hormones insulin-like growth factor-1 (IGF-1) and insulin attenuated several metabolic changes associated with cancer cachexia. In the present study, we evaluated the effect of these hormones on the cachexia associated with colon-26 (C-26) tumor. Healthy age-matched and tumor-bearing mice were treated with two daily doses of IGF-1 (50 micrograms/kg in toto), or insulin (1 U in toto). Determinants of cachexia were body and tumor weight, epididymal fat pad and serum glucose concentrations. Neither IGF-1 nor insulin treatment had a significant effect on the cachectic parameters of C-26-bearing mice. These hormones were biologically active, being capable of inducing weight gain in hypophysectomized mice and hypoglycemia, respectively. Although IGF-1 and insulin have been used to treat cancer-related weight loss, the research presented here suggests that the beneficial effect of these hormones is not universal.

Mechanisms of cachexia induced by T-cell leukemia in the rat

Body wasting (cachexia) is a common feature of cancer and a major cause of morbidity and mortality. The mechanisms underlying cachexia are largely unknown, and studies in experimental animals have focused mainly on solid tumors. Therefore, the objective of the present study was to quantify and investigate cachexia in experimentally induced T-cell leukemia in the rat. Induction of leukemia by serial passage (injection of cervical lymph node suspension) resulted in a rapid increase in white blood cell (WBC count, hypertrophy of the spleen (by day 11), and severe morbidity within 17 to 18 days. Body weight gain and food intake declined steadily in leukemic animals from day 12, although weight loss was significantly greater in pair-fed, nonleukemic animals. However, leukemic rats had a lower body fat content and higher water content than pair-fed animals on day 18, so the measurement of body weight significantly underestimated the severity of cachexia. Resting oxygen consumption (VO2), measured during the light phase, declined in pair-fed animals from day 13, but was elevated in leukemic rats on days 12 to 18 by 25% (P < .05, one-way ANOVA) compared with pair-fed rats and by 7% (P < .05, one-way ANOVA) relative to free-feeding controls. Hypermetabolism was associated with an increase in brown adipose tissue (BAT) activity (74% and 89%, respectively, P < .05, one-way ANOVA) in leukemic rats compared with control and pair-fed groups. Effects of leukemia on VO2 and BAT were prevented by administration of the adrenergic antagonist, propranolol. These results indicate that T-cell leukemia in the rat results in rapid and severe cachexia, which is largely due to marked hypophagia, but is also accompanied by inappropriately high rates of energy expenditure that are mediated by sympathetic activation of BAT thermogenesis.

From laboratory to bedside: new strategies in the treatment of malnutrition in cancer patients

The objective of this review is to present and discuss the current and the possible future perspectives of artificial nutrition in preventing and treating cancer cachexia. English-language studies published in the last 25 years were retrieved using MEDLINE, bibliographies and consultation with experts. MEDLINE search terms included "cancer," "malnutrition," and "nutritional support." In vivo and in vitro controlled studies were selected, and data from each study were independently abstracted by the authors. Data obtained indicate that cancer cachexia is a common manifestation of advanced malignant disease, characterized by marasmus due to impaired nutrient metabolism, weight loss, and anemia. In patients, the presence of cachexia increases morbidity and mortality, delays or impedes the delivery of the adequate treatment, reduces the efficacy of anti-neoplastic therapy, and impairs patient's quality of life. Indirect evidence indicates that cancer cachexia is mediated by circulating cytokines, produced by the host in response to the presence of the malignancy. In the past two decades, nutritional support was used to counteract the detrimental effect of cancer cachexia on the host, but with limited success. More recently, the better understanding of the mechanisms of cancer cachexia and the identification of pharmacologic effects provided by specific nutrients, has formed the rationale for a "new" mode of nutrition therapy/nutritional support, adding pharmacotherapy to adjunctive initial care.

Macrophage-derived tumor necrosis factor and tumor-derived of leukemia inhibitory factor and interleukin-6: possible cellular mechanisms of cancer cachexia

BACKGROUND

The cellular basis for augmented cytokine production in the tumor-bearing host is not known. Recently leukemia inhibitory factor (LIF) and interleukin (IL)-6, produced by a variety of tumors, have been implicated as mediators of cachexia.

METHODS

Five murine tumor cell lines were tested for the production of these cytokines. 4JK tumor was further tested to determine if IL-1, tumor necrosis factor (TNF), or cocultivation with RAW 264 cells augmented IL-6 or LIF production.

RESULTS

4JK from in vivo tumors produced significantly more IL-6 than did 4JK from culture, indicating that tumor production of IL-6 and LIF is potentially augmented by infiltrating macrophages. When 4JK was cocultured with RAW 264 cells, TNF, or IL-1 in vitro, a three- to 15-fold increase in tumor production of LIF and IL-6 was noted (p2 < or = 0.03). Conversely, in coculture experiments performed with a neutralizing TNF antibody, a 50% reduction in tumor production of LIF ad IL-6 was noted (p2 < 0.04). Resting RAW cells produced only minimal quantities of TNF; however, when RAW cells were exposed to tumor-conditioned supernatant from 4JK, their TNF production was markedly increased.

CONCLUSIONS

In the tumor microenvironment, host macrophages may be activated and produce inflammatory cytokines such as TNF. Local TNF then appears to act on tumor cells to stimulate production of IL-6 and LIF. Enhanced tumor production of cytokine mediators may contribute to deleterious effects of neoplastic growth on the host.

The effect of caloric density of food on energy intake and body weight in tumor-bearing rats

Anorexia and weight loss are major problems for cancer patients and are associated with increased cancer morbidity and mortality. The current clinical approach is to encourage high calorie food intake. In the present study, we used an animal model of tumor-induced anorexia to evaluate the effect of feeding a high caloric diet on food and caloric intake and body weight of tumor-bearing rats. Tumor-bearing rats fed a diet containing 4.7 kcal/g reduced the amount of food they ate to equal the caloric intake of rats fed a diet containing 3.7 kcal/g. Body weight and tumor growth were not affected by the diet intervention. These data suggest that energy intake is regulated in tumor-bearing rats as it is in healthy animals, albeit at a lower level. These data have implications for further study of the effects of nutritional supplements on food intake and nutritional status of cancer patients.

Diminished visceral adipose tissue in cancer cachexia

To estimate the relationship between the visceral adipose tissue (AT) area and cancer cachexia, 13 cachectic patients (7 males, 6 females; age 65.2 +/- 11.0 years; body mass index 20.8 +/- 4.1 kg/m2) were examined by computed tomography (CT) scanning. Cachectic cancer patients who had a 10% decrease of body weight and died within 6 months because of gastrointestinal carcinoma had a significantly smaller visceral AT area than control subjects (mean +/- sd: 43.9 +/- 42.2 cm2 vs. 93.4 +/- 56.0 cm2, P < 0.05, P = 0.014). Otherwise, there were no significant differences between the visceral AT areas of cachectic cancer patients and those of cancer patients with resectable tumors treated by curative operation (mean +/- sd: 68.8 +/- 57.7 cm2) (NS, P = 0.206). There was, however, a tendency for cachectic cancer patients to have a smaller visceral AT area than those with resectable tumors. This result suggests that the visceral AT area is not preserved in the cachectic state associated with cancer.

Decrease of glutaminase expression by interferon-gamma in human intestinal epithelial cells

BACKGROUND

Glutaminase, the principal enzyme of glutamine hydrolysis, breaks down glutamine to supply energy and intermediates for cell growth and is present in high concentrations in replicating tissues such as intestinal epithelium and malignant tumors. In the host with cancer, glutaminase activity in the gut mucosa diminishes as the tumor grows, but the regulation of this response is unknown. Because cytokines may regulate the altered glutamine metabolism that is characteristic of the host with cancer, we studied the effects of cytokines on gut mucosal glutaminase expression in vitro using the human enterocytic Caco-2 cell line.

METHODS

Differentiated confluent cells were incubated with interleukin (IL)-1, IL-6, tumor necrosis factor, or interferon-gamma (IFN-gamma). After a 12-h incubation, glutaminase-specific activity and kinetic parameters (maximal enzyme activity [Vmax] and enzyme affinity [Km]) were determined. Glutaminase protein concentration was determined by Western blot analysis using a rabbit antirat polyclonal antibody. Total cellular RNA was extracted for Northern hybridization and radiolabeled with a glutaminase cDNA probe.

RESULTS

Of the cytokines studied, only IFN-gamma altered glutaminase activity. Kinetic studies indicated a decrease in activity secondary to a 25% decrease in Vmax with no change in Km, consistent with a reduction in the number of glutaminase molecules rather than a change in enzyme affinity. Glutaminase protein was decreased 50% in IFN-gamma-treated cells when compared with controls. This decrease was dose-independent and was associated with a concomitant 75% decrease in glutaminase messenger RNA levels. These reductions in message and protein translated into a 60-80% decrease in functional glutaminase-specific activity.

CONCLUSIONS

This IFN-gamma-mediated decrease in glutaminase activity may be one mechanism by which gut glutamine metabolism is diminished as the tumor grows and becomes the principal organ of glutamine use.

Characterization of differentiation factor/leukaemia inhibitory factor effect on lipoprotein lipase activity and mRNA in 3T3-L1 adipocytes

Alterations in lipid metabolism characterized in major part by a decrease in lipoprotein lipase (LPL) activity in adipose tissue are a central feature of cachexia from chronic infection or malignancy. These metabolic derangements may be mediated in large part through endogenous host proteins produced in response to various pathological stimuli. Differentiation factor/leukaemia inhibitory factor (D-factor) is a cytokine whose functions overlap those of tumour necrosis factor-alpha (TNF), IL-6 and IL-1. Recombinant murine D-factor produced a dose- and time-dependent inhibition of heparin-releasable LPL activity in differentiated 3T3-L1 adipocytes. Although 2-10 fold less potent than recombinant murine TNF, D-factor inhibited LPL activity at concentrations of 1-10 ng/ml. When added together, D-factor and TNF produced a synergistic inhibition of LPL activity. Interleukin 6 (IL-6) was 100-fold less potent than D-factor; 0.1 ng/ml of D-factor or 10 ng/ml of IL-6 caused a 50% inhibition of LPL activity. D-factor and TNF increased IL-6 production in 3T3-L1 cells. Ten ng/ml of D-factor or 1.0 ng/ml of TNF stimulated the release of < 1 ng/ml of IL-6 and inhibited LPL activity to 11 +/- 3% and 3 +/- 2% of control, respectively, whereas 50 ng/ml of recombinant IL-6 was required to decrease LPL activity to 24 +/- 19% of control. TNF produced a marked decrease in LPL mRNA, whereas D-factor had minimal or no effect at doses which inhibited LPL activity almost completely. Western blot analysis of cell extracts showed that TNF caused a greater decrease in LPL protein production than D-factor.2+ with TNF, may contribute to the manifestations of cachexia.

Tumor-derived components were responsible for suppression of ornithine decarboxylase activity in the rat wounded skin

To elucidate the principal cause of delayed wound healing in a tumor-bearing host, the effect of Yoshida sarcoma-derived components on dermal wound healing was investigated in rats with the aid of ornithine decarboxylase (ODC) activity and in vivo bromodeoxyuridine (BrdU) labeling index. The ODC activity in the wounded skin decreased 3 and 7 days after intraperitoneal inoculation of Yoshida sarcoma cells (378.0 +/- 37.3 on Day 3, 280.0 +/- 140.0 on Day 7 vs. 809.3 +/- 109.5 pmol/mg protein/hour on Day 0). When administered 24 hours before and immediately after wounding, the crude nuclear component of the tumor cells significantly decreased the ODC activity in the wounded skin as compared with the control (185.9 +/- 159.8 vs. 534.0 +/- 59.1), but the non-nuclear component was not effective. When nuclear extracts of Yoshida sarcoma cells were intraperitoneally administered immediately after wounding, the 0.15 M or 0.35 M NaCl extract significantly suppressed ODC activity in the wounded skin (233.5 +/- 14.5 and 352.3 +/- 63.2 pmol/mg protein/hour, respectively) in comparison to the control (445.9 +/- 73.6). The BrdU labeling index of epidermal basal cells adjacent to the edge of the wound decreased up to 52% of the control by injection of the 0.15 M extract. It seems that tumor-derived nuclear components may be responsible for delayed wound healing which is commonly observed in cancer cachexia.

Mechanisms of paraneoplastic syndromes of colon-26: involvement of interleukin 6 in hypercalcemia

The precise mechanisms responsible for increased calcium levels in patients with cancer are not fully understood. In a recent study, the participation of interleukin (IL)-6 as an important mediator of key parameters of cancer cachexia in the colon-26 adenocarcinoma was reported. Here, we show that in addition to cachexia, C-26 tumour bearing mice also develop hypercalcemia. Treatment of these mice with 5' deoxyfluorouridine significantly reduces tumour size and inhibits both hypercalcemia, cachexia, and elevated serum IL-6. Moreover, monoclonal antibody to mouse IL-6 prevents both the cachexia and the hypercalcemia and reduces serum IL-6 levels in C-26 tumour bearing hosts. The administration of a bisphosphonate compound (Clodronate) reverses the hypercalcemia but has no effect on tumour burden, serum IL-6 levels, or wasting. We conclude that tumour-derived IL-6 plays a role in the pathogenesis of the C-26 associated hypercalcemia, and that the increase of serum calcium does not by itself mediate cachexia.

Cytokines and their role in the pathophysiology of cancer cachexia

Cancer cachexia describes a syndrome that consists of weight loss, and abnormalities in carbohydrate, protein, and lipid metabolism, which result in a state of persistent net negative energy balance. Patients suffering from cancer cachexia have a significantly shortened survival after cancer treatment. Recent experimental studies have focused on the belief that the mechanisms of cancer cachexia involve the host's production of inflammatory cytokines, which through broad physiologic actions ultimately lead to a chronic state of wasting, malnourishment, and death. Cytokines that have been thought to play a role in the pathophysiology of cachexia include tumor necrosis factor, interleukin-1, interleukin-6, interferon-gamma and differentiation factor. It has become clear that these cytokines have overlapping physiologic activities, which makes it likely that no single substance is the sole cause of cachexia in most cancer patients. Only further investigation may make it possible to more clearly define the role of cytokines in the pathophysiology of cancer cachexia. Specific strategies to reverse the cachectic effects of these substances may then be developed to ultimately improve cancer treatment.

The early cancer anorexia paradigm: changes in plasma free tryptophan and feeding indexes

Tumor growth is accompanied by an anorexia mediated by humoral factors that appear to influence appetitive mechanisms in the brain. Because tumor resection is followed by resumption of normal food intake, the circulating anorexigenic substance(s) are produced either by the neoplastic tissue or by the host in response to the tumor. Increased levels of plasma free tryptophan and plasma ammonia have been proposed to mediate cancer anorexia. With animal models, it is often difficult to ascertain whether changes in food intake depend upon metabolic changes or the progressively increasing tumor mass per se. The feeding patterns and biochemical changes that occur during tumor growth were evaluated in 96 male Fischer rats that were inoculated with 10(6) methylcholanthrene sarcoma cells or saline (controls). Rats were placed into metabolic cages equipped with an Automated Computerized Rat Eater Meter to continuously determine meal size and meal number. Plasma free tryptophan and ammonia were evaluated 6, 10, 16, 18, 22, and 26 days after tumor inoculation. Anorexia developed by day 17-18, when food intake started to decrease via a decrease in meal size but not meal number and reached 60% of control by day 26. However, long before anorexia developed, free tryptophan was significantly higher 6 days after tumor inoculation, and the greatest increase occurred after 18 days. Ammonia did not differ from control at any time. Data confirm tumor-associated increases in plasma free tryptophan that occurred before the manifestation of anorexia and support a possible role of brain serotonin in cancer anorexia.