Michael H. Torosian

Alteration of tumor cell kinetics by pulse total parenteral nutrition. Potential therapeutic implications.

Previous work has demonstrated that substrate‐induced alterations of tumor metabolism can be exploited to potentiate tumor response to cycle‐specific chemotherapy (methotrexate, Adriamycin (doxorubicinl). This study was performed to investigate the biologic mechanism responsible for this phenomenon by determining the effect of short‐term total parenteral nutrition (TPN) on tumor cytokinetics. Forty‐two female Lewis/Wistar rats with subcutaneous mammary tumor implants (AC‐33) underwent superior vena caval cannulation, and were randomized to receive either TPN or normal saline intravenously. Animals receiving TPN were killed at 2, 6, 12, 24, and 48 hours after initiating TPN; control animals given normal saline were killed at 0, 24, and 48 hours after randomization. At the time the animals were killed tumor cytokinetic analysis was performed by flow cytophotometry. The percentage of tumor cells in S‐phase was significantly increased in animals after only 2 hours of TPN (55.5 ± 9.1%) compared with the control group (43.7 ± 7.7%) (P < 0.01). The ratio of sensitive/resistant tumor cells to S‐phase‐specific chemotherapy was effectively increased in animals receiving adjuvant TPN (1.31 ± 0.43) compared with control animals (0.80 ± 0.25) (P < 0.015). This alteration in tumor cytokinetics provides one explanation for the enhanced tumor response to cycle‐specific chemotherapy previously observed with pulse TPN administration. Cancer 53:1409‐1415, 1984.

Growth hormone, insulin, and somatostatin therapy of cancer cachexia

Background. Cancer cachexia is associated with a decreased insulin:glucagon ratio. The authors hypothesized that the decrease in this anabolic hormone index is largely responsible for the progressive catabolism characteristic of cancer cachexia. Previous studies of insulin therapy alone in treating cancer cachexia have yielded limited success due to insulin‐induced hypoglycemia and subsequent glucagon secretion. The current study was performed to determine the effect of combined hormone therapy (growth hormone, insulin, and somatostatin) on tumor growth, metastasis, and host metabolism.

Growth Hormone Inhibits Tumor Metastasis

The effect of growth hormone on tumor growth and metabolism in the tumor‐bearing host is unknown. This study was done to determine the effect of recombinant growth hormone on primary tumor growth, tumor metastasis, and carcass weight in tumor‐bearing animals. Twenty‐seven female Lobund/Wistar rats with subcutaneous prostate tumor implants (PA‐III) were randomized to receive a standard protein diet (22.0% protein; 4.27 kcal/g) or an isocaloric, protein‐depleted diet (0.03% protein; 4.27 kcal/g) ad libitum orally. One half of the animals in each group were randomized to receive daily injections of either recombinant growth hormone (1000 mU/kg/day intramuscularly) or placebo (saline) for 14 days. A significant increase in body weight was observed in growth hormone‐treated animals without acceleration of primary tumor growth. Spontaneous pulmonary metastasis was inhibited significantly in animals in both dietary groups treated with growth hormone. Thus, growth hormone selectively supports host growth and inhibits pulmonary metastasis in this tumor‐bearing animal model. The potential metabolic effects and clinical consequences of treating cancer patients with growth hormone is discussed.

Effect of glutamine on tumor and host growth

AbstractBackground: Oral glutamine supplementation has been found to support gastrointestinal mucosal growth and increase intestinal and systemic toxicity after chemotherapy and radiation therapy. Glutamine is also an important nutrient for rapidly proliferating tumor cells. However, it is not clear whether long-term glutamine supplementation in the tumor-bearing host has a selective benefit for host growth or tumor cell proliferation. Methods: To study the effect of glutamine in tumor-bearing animals, 30 Lewis/Wistar rats with subcutaneous mammary tumor implants (MAC-33) were randomized to receive a 3% glutamine- or 3% glycerine-enriched (control) diet for 25 days. Results: No significant difference was found in carcass weight, primary tumor weight, or spontaneous pulmonary metastasis with glutamine supplementation. Tumor cell cycle kinetics (aneuploidy, %S and %S [synthetic] + G2/M [growth fraction]) were similar between glutamine-supplemented and control animals. A trophic effect of glutamine on distal ileal mucosa was seen with increased DNA content (344±68 vs. 184±38 µg/100 mg tissue) (p<0.05) and RNA content (435±44 VS. 335±30 µg/100 mg tissue) (p=0.06) compared with control animals. No detectable differences were observed in liver or muscle, or in tumor DNA, RNA, or protein content. Conclusions: These findings confirm the trophic effect of glutamine on small intestinal mucosa and suggest that glutamine can be administered to the tumor-bearing host over a long period of time without significantly stimulating tumor growth kinetics or metastasis.

Reversal of tumor-associated hyperglucagonemia as treatment for cancer cachexia*

BACKGROUND The tumor-bearing state is associated with increased circulating glucagon levels that may play an etiologic role in cancer cachexia. The secretion of glucagon can be inhibited with long-term somatostatin analogs, and, in combination with insulin, should maximally reverse the low insulin/glucagon ratio seen in cancer cachexia. The goal of this study is to examine the effect of somatostatin (octreotide) and insulin in a model of cancer cachexia and to determine whether inhibition of glucagon secretion will reverse some of the abnormalities in carbohydrate metabolism to selectively benefit host versus tumor metabolism. METHODS Sixty-seven female Lewis rats were subcutaneously inoculated with 1 x 10(6) metastasizing mammary adenocarcinoma tumor cells. On day 30 the animals were randomized into four groups to receive (1) tumor-bearing control (saline injections); (2) octreotide, 150 microgram/kg intraperitoneally twice a day; (3) neutral protamine Hagedorn insulin, 5 units/kg subcutaneously twice a day; or (4) both insulin and octreotide injections. A fifth group of non-tumor-bearing controls was included. The animals received treatment for 5 days and were then killed. RESULTS The tumor-bearing state was found to be associated with an increase in glucagon levels and a significant decrease in the insulin/glucagon ratio. The combination of somatostatin+insulin resulted in a 23-fold increase in the insulin/glucagon ratio without causing significant host morbidity from hypoglycemia. This increased insulin/glucagon ratio was associated with increased carcass weight, increased muscle weight, increased muscle protein, increased liver cellular protein, increased liver microsomal P-450 content, and decreased tumor protein content compared with the tumor-bearing controls. These results were not seen with insulin or somatostatin alone. Hepatic lactate dehydrogenase, glucose-6-phosphatase, and fructose-1, 6-diphosphatase activities were increased as a result of combination hormone treatment. CONCLUSIONS Combination hormone treatment with somatostatin and insulin results in a marked increase in the insulin/glucagon ratio and a selective nutritional benefit to the host. The inhibition of tumor-associated hyperglucagonemia should be considered in the treatment of cancer cachexia.

Stimulation of Tumor Growth by Nutrition Support

Controversy exists regarding the use of nutrition support in the cancer patient. Although nutrition support can clearly improve host nutritional status and restore immunoconfidence, the efficacy of nutrition support to reduce morbidity and mortality associated with antineoplastic therapy is questionable. A potential concern with the use of nutrition support in the tumor-bearing host is stimulation of primary tumor growth and metastasis. Numerous animal studies clearly demonstrate that oral and parenteral nutrition can significantly stimulate tumor cell proliferation and distant metastasis. Although cellular kinetic studies in humans have shown alterations after parenteral nutrition, objective measures of tumor growth, metastasis and tumor protein synthesis have not been affected by parenteral nutrition. This chapter summarizes the research and clinical work regarding the effect of nutrients on tumorigenesis, primary tumor growth, and metastasis in both animal and human tumors.

Effect of growth hormone and protein intake on tumor growth and host cachexia.

BACKGROUND Growth hormone supplementation has been shown to stimulate muscle protein synthesis and to improve nitrogen balance in a variety of catabolic states. The role of growth hormone to support the tumor-bearing host is complicated by the risk that growth hormone or its intermediaries may stimulate tumor growth. The purpose of this study is to examine the effect of growth hormone supplementation in tumor-bearing rats. This is studied in the protein-fed and protein-starved state in an attempt to isolate a selective benefit for the host over the tumor. METHODS Forty Lewis rats bearing a metastatic mammary adenocarcinoma (MAC-33) were divided into four groups: one receiving a regular diet plus saline solution, one receiving a regular diet plus growth hormone (1 IU/kg/day), one receiving protein-depleted diet plus saline solution, and one receiving a protein-depleted diet plus growth hormone. After 25 days of growth hormone treatment, animals were killed to determine primary tumor size, tumor/carcass ratio, host organ composition, pulmonary metastasis, and serum amino acid levels. RESULTS The tumor/carcass ratio was decreased as a result of growth hormone treatment in both the protein-fed and protein-starved groups. Growth hormone supplementation resulted in increased carcass weight, muscle weight, and muscle protein content in the protein-fed, tumor-bearing animals (p < 0.05). In the protein-starved, tumor-bearing rats growth hormone supplementation resulted in a significant decrease in tumor volume and tumor protein content. Amino acid analysis suggests that the amino acid tyrosine is a rate-limiting substrate for tumor cell proliferation in this model. CONCLUSIONS Growth hormone has a differential effect on tumor and host growth in the protein-fed and protein-starved state. Growth hormone supplementation inhibited tumor growth in protein-deprived animals. This is most likely accomplished indirectly by limiting amino acid substrate availability to the tumor.

Enhanced Tumor Response to Cycle-Specific Chemotherapy by Parenteral Amino Acid Administration

Forced feeding has been shown to effectively stimulate tumor metabolism in numerous animal models. Significant acceleration of tumor growth by exogenous nutrient administration is generally considered to be detrimental to the host. The present study was performed to determine if substrate-induced alterations in tumor metabolism could be exploited to enhance tumor response to cycle-specific chemotherapy. Following subcutaneous mammary tumor implantation (AC-33) and protein depletion, 39 female Lewis/Wistar rats were randomly assigned to one of four nutritional regimens for 48 hr: (1) protein-depleted food (0.03% protein) ad libitum po, (2) parenteral carbohydrate (18.6% dextrose), (3) parenteral amino acids (2.8% amino acids), or (4) total parenteral nutrition (18.6% dextrose/2.8% amino acids). Methotrexate (5 mg/kg im) was administered to all animals 2 hr after initiating these nutritional regimens. Tumor volume and host toxicity were monitored throughout the study. At sacrifice, significant reduction in tumor volume was observed in animals receiving parenteral amino acids (0.37 +/- 0.24 cm3) and total parenteral nutrition (0.25 +/- 0.18 cm3) compared to the group receiving protein-depleted food po (0.70 +/- 0.22 cm3) (p less than 0.01). In this animal model, the parenteral administration of amino acids with or without the addition of hypertonic dextrose was found to effectively potentiate tumor response to methotrexate without increasing host toxicity.

Reduction of methotrexate toxicity with improved nutritional status in tumor-bearing animals

The administration of chemotherapy in clinical situations is limited frequently because of the associated toxicity to normal bone marrow cells, gastrointestinal epithelium, and other host tissues. Although nutritional support has been advocated to reduce chemotherapy‐related toxicity in cancer patients, few studies substantiate this clinical impression. The current study was performed to determine the role of nutritional status and enteral nutrient intake as determinants of methotrexate (MTX) toxicity in a well‐controlled, tumor‐bearing animal model. After subcutaneous mammary tumor (AC‐33) inoculation, 56 female Lewis/Wistar rats were assigned randomly to one of the following two nutritional regimens for 14 days: (1) protein‐depleted chow (PC) (0.03% protein; 4.27 kcal/g) or (2) standard chow (RC) (22.0% protein; 3.50 kcal/g). After 7 days of dietary control, all animals received one of three weight‐adjusted doses of MTX (5, 10, or 20 mg/kg intramuscularly [IM]) or placebo. All animals received leucovorin rescue (0.6 mg IM) at 6 and 24 hours after MTX injection. Improved nutritional status was associated with a significant reduction in objective measures of MTX‐related morbidity and mortality. At low doses of MTX (5 and 10 mg/kg), the mean duration of clinical signs of toxicity (i.e., hair loss, lethargy, and diarrhea) and severity of leukopenia were greater in protein‐depleted (PD) animals. With high‐dose MTX (20 mg/kg), mortality was increased significantly in PD animals (100%) compared with well‐nourished animals (0%). Equivalent tumor response was observed in PD and well‐nourished animals. Thus, improved nutritional status by enteral nutrition reduced the morbidity and mortality associated with MTX significantly in this tumor‐bearing animal model.

Enhanced tumor response to cycle-specific chemotherapy by pulse total parenteral nutrition

Exogenous nutrient administration has been shown to significantly stimulate tumor growth in numerous animal models. The present study was performed to determine if substrate-induced alterations in tumor metabolism could be exploited to potentiate tumor response to cycle-specific chemotherapy. Following subcutaneous mammary tumor (AC-33) implantation, 55 female Lewis/Wistar rats were randomly assigned to one of three nutritional regimens for 48 hr: (1) protein-depleted chow (0.03% protein) ad lib per os, (2) standard rat chow (22.0% protein) ad lib per os, or (3) total parenteral nutrition (TPN; 18.6% dextrose/2.8% amino acids). One-half of the animals in each group received a single dose of methotrexate (5 mg/kg im) while the remaining animals received placebo (saline) injections. At sacrifice, methotrexate-treated animals receiving TPN demonstrated a significantly smaller tumor volume (0.47 +/- 0.44 cm3) compared to animals given either protein depleted chow (1.30 +/- 0.76 cm3) or standard rat chow (1.34 +/- 0.83 cm3) (P less than 0.01). In this animal model, adjuvant TPN was found to significantly potentiate tumor response to cycle-specific chemotherapy with no detectable exacerbation of host toxicity.