Enhanced tumor response to cycle-specific chemotherapy by parenteral amino acid administration

Effects of parenteral nutrition support and chemotherapy on the phasic composition of tumor cells in gastrointestinal cancer

BACKGROUND

Some clinical studies report the effects of parenteral nutrition in malnourished cancer patients, but few discuss the tumor response to parenteral nutrition plus chemotherapy. If used in combination, the antitumor activity of chemotherapeutic agents may compensate for the tumor stimulation of parenteral nutrition.

METHODS

Ninety-two patients with operable gastrointestinal cancer and malnutrition were randomly assigned to four interventions that were administered for 7 days preoperatively: parenteral nutrition alone, parenteral nutrition plus chemotherapy, chemotherapy alone, or no treatment (control). The preintervention and postintervention DNA content, DNA index, percentage of cells in S phase, and tumor cell sensitivity to chemotherapy were measured using image cytometry.

RESULTS

Parenteral nutrition resulted in a significant proliferation of tumor cells and a significant increase in the sensitivity of tumor cells to chemotherapy; these effects were not seen in tumors of patients receiving parenteral nutrition plus chemotherapy. There was, however, a nonsignificant increase in tumor cell proliferation and sensitivity to chemotherapy in the tumors of subjects receiving combined therapy compared with those of subjects who received chemotherapy alone. The postintervention nutritional status of both the parenteral nutrition group and the parenteral nutrition plus chemotherapy group were significantly better than that of the control group and the chemotherapy group. The short-term, postoperative clinical outcomes in the chemotherapy group were significantly worse than those in the other three groups.

CONCLUSIONS

These results indicate that combining chemotherapy and nutrition support preoperatively for malnourished patients with gastrointestinal cancer improves short-term nutritional status without increasing the proliferation of tumor cells and prevents the postoperative complications that occur when such patients are given chemotherapy without nutrition support. The results also suggest--but do not prove--that parenteral nutrition may increase the effectiveness of chemotherapy in malnourished patients.

Parenteral nutrition at home in advanced cancer patients

There is controversy regarding the utility of parenteral nutrition in advanced cancer patients. In selected populations, such as those with digestive tract cancers, death may result from the absence of oral intake and not progression of disease. In some cases, patients and relatives request that artificial nutrition begun in the hospital continue after discharge. Clinical experience with the management of home parenteral nutrition in 13 cancer patients is described to highlight the ethical and technical problems that emerge during the treatment of such patients.

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.

Abnormal substrate metabolism and nutritional strategies in cancer management

Impairment of the nutritional state plays a major role in the morbidity and mortality of cancer patients. However, the opportunity of providing artificial nutritional support to these patients is still debated, because of the concern that energy substrates administered to replete the host may concomitantly stimulate tumor growth. A correct nutritional approach to cancer patients should thus be based on a thorough knowledge of both host and tumor metabolic needs and host-tumor metabolic interactions. Specific modifications of plasma levels of glucogenic, aromatic, sulfur-containing and branched-chain amino acids have been demonstrated in cancer patients, indicating a specific influence of the tumor on amino acid metabolism. Little is known about protein metabolism in neoplastic tissue. Interference with tumor growth has been attempted by deprivation of single amino acids with controversial results. Increased gluconeogenesis and insulin resistance are responsible for the two main abnormalities in carbohydrate metabolism in cancer patients, namely increased glucose turnover and impaired glucose tissue disposal. Lipid metabolism is also affected by the neoplasm: soluble factors such as "lipid-mobilizing factor" lead to increased fat mobilization from adipose tissue; plasma elimination of exogenous triglycerides has also been found to be reduced probably because of a tumor-related decrease in lipoprotein lipase activity. The differences in glucose and fat utilization between tumor and host should be considered in the nutritional approach to cancer patients. Data in this respect are controversial and have been obtained only in experimental animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of energy substrate manipulation on tumour cell proliferation in parenterally fed cancer patients

The effects of isocaloric carbohydrate-based vs. fat-based total parenteral nutrition (TPN) regimens on cancer cell proliferation and host nutritional status were evaluated in 27 patients with tumours of the gastro intestinal tract consecutively assigned to receive for 14 days: a glucose-based (A) or a lipid-based (B) TPN formula, or an oral diet (C) isocaloric and isonitrogenous to A and B. Cancer cell replication rate was evaluated by thymidine labelling index (LI) on tumour samples before and at the end of each nutritional regimen. The number of replicating cells increased by 32.2% in patients receiving regimen A. LI decreased by 24.3% in patients given regimen B. LI values were slightly increased (+15%) in patients maintained on regimen C. Nutritional status remained within normal limits. None of the LI changes observed between and within the three arms of the trial were found to be statistically significant. Thus we failed to prove that glucose consistently stimulates or lipids inhibit tumour proliferation despite a trend in this sense.

Nutritional modulation of tumor growth

The relationship between tumor and host tissue proliferation as a function of protein calorie deficiency followed by balanced nutritional repletion was examined in a series of C3H female mice with MA16/C tumors. Tumor and host tissue DNA synthesis was determined in animals with subcutaneously implanted tumors who were randomized to either regular diet (RD) or a totally protein-free diet (PFD) for 5 days followed by refeeding for 4, 8, 12, 24, 36, 48, or 72 hr. Animals maintained on a protein-free diet demonstrated a decrease in DNA synthetic activity in both tumor and host tissues. Following refeeding of a regular diet to animals fed the protein-free diet, resumption of DNA synthesis in tumor preceded that of liver and was greatest by four hours of refeeding. In the liver, return of DNA synthetic activity was delayed but exceeded control levels by 36 hr. Compared to our previous studies examining the effects of starvation, we found that an isocaloric protein-free diet caused a smaller decrease in tumor DNA synthetic activity and an earlier resumption in tumor proliferation with the reinstitution of a normal protein diet. These studies suggest a nutrient-specific response for tumor and host tissues with nutritional deprivation and refeeding.

Causative factors for decreased pulmonary metastasis in parenterally fed mice

Total parenteral nutrition (TPN) with fat and/or glucose as the caloric source is associated with a decrease in pulmonary metastasis in mice bearing subcutaneously implanted Lewis lung carcinoma. Five groups of white mice bearing Lewis lung carcinoma were assigned to receive various isocaloric and isonitrogenous oral and parenteral feedings: TPN, utilizing all nonnitrogen energy from glucose; per os, utilizing all nonnitrogen calories from glucose; electrolyte, utilizing nonnitrogen calories provided from a balanced casein diet and receiving an isovolemic infusion of electrolytes in the same composition as the TPN formula; 1/4 normal saline, also consuming the casein diet and receiving an isovolemic infusion of 1/4 normal saline; and an oral casein control (CON) without infusion. Results showed that there were no significant differences in tumor volume changes or tumor doubling time among the groups. However, tumor weight was significantly lower in groups receiving the TPN solution either orally or parenterally in comparison to the oral casein control. Pulmonary metastases were significantly lower in all parenteral groups, irrespective of solution composition, compared to the CON group. Thus it appears that parenteral fluid load rather than composition of the solution is the causative factor for the decrease in pulmonary metastases.

Amino acid requirements of a rat sarcoma as determined by a stem cell assay

Knowledge of the amino acid requirements of a neoplasm is valuable in determining optimal nutritional support and antineoplastic therapy for the tumor-bearing host. The standard human tumor stem cell assay (HTSCA) was modified by reducing an individual amino acid below the normal plasma concentration of the Fischer 344 rat. All other amino acids were maintained at levels sufficient for normal HTSCA tumor colony growth. Twenty-two amino acids were tested at a mean concentration of 12% (range 3% to 35%) of their normal plasma level. Results indicated that all amino acids except L-glutamine and L-asparagine were present in sufficient quantity for normal tumor growth. Dose-response curves have shown more than 70% inhibition of tumor growth with a glutamine concentration of 50% and an asparagine concentration of 25%. Glutamine and asparagine levels of 4% and 1%, respectively, resulted in 100% inhibition. The data indicate that rat sarcoma stem cells are sensitive to decreased glutamine and asparagine concentrations.

Nutritional support in the cancer-bearing host. Effects on host and tumor

Cancer patients have the highest prevalence of malnutrition of any group of hospitalized patients. The potential causes of this malnutrition are numerous, as elements of both starvation and stress are evident in the cancer-bearing host. The presence of the tumor alone may lead to reduced intake of nutrients and treatment modalities of surgery, chemotherapy, and radiation therapy further exacerbate nutritional deficits. It is clear that the tumor requires energy substrates to grow, and that these substrates are exacted from the host. Animal studies identify progressive nutritional depletion concomitant with increasing tumor growth during ingestion of a regular diet. This appears predominantly due to reduced dietary intake in addition to host metabolic alterations. In animal/tumor models deliberate dietary protein depletion results in severe host weight loss, but also causes diminished tumor growth rates. Dietary manipulation in these animal/tumor models have demonstrated methods of improving tumor response to chemotherapy by manipulation of tumor growth rates. In addition, drug-pharmacokinetics have been altered by dietary manipulation. However, data from animal/tumor models are not directly applicable to man since the tumor in animals usually results in the death of the host within six to eight weeks. Nevertheless, controlled laboratory studies in animals provide basic metabolic information which promotes understanding of host/tumor relationships in man. In cancer patients malnutrition has prognostic value, leads to a distortion of body composition with erosion of body protein and fat stores, and compromises the delivery of adequate therapy. There is no direct objective evidence of accelerated tumor growth in humans with cancer who receive nutritional support as part of their treatment regimen. The host benefits to the extent that body composition is at least maintained during the period of nutritional repletion. Thus, nutritional support provides support to the patient during periods of treatment and dietary deprivation. No improvement in the tumor's response to therapy, however, has been demonstrated by this approach.

Refeeding differentially affects tumor and host cell proliferation

Tumor and host tissue DNA synthesis in C3H female mice with MA16/C tumors were examined for the effects of starvation and refeeding. Animals with subcutaneously implanted tumors were randomized to either regular diet or starvation for 48 hr followed by refeeding for 6, 12, 24, 48, or 72 hr. With starvation, both tumor and host tissues demonstrated a decrease in DNA synthetic activity. After refeeding, resumption in DNA tumor synthesis preceded that of host tissues and was greatest within the first 6-12 hr. Host tissue DNA synthetic activity resumed at different times in the various tissues examined with bone marrow being earlier than spleen or liver. The differential time course between induction of tumor and host DNA synthesis could allow a more precise modeling in studies dealing with the interaction of nutritional repletion and antitumor therapy.

The effect of energy substrate manipulation on tumor growth and metastasis and intermediary metabolism in the parenterally fed mouse

The effect of N-free energy substrate manipulation on tumor growth and metastasis, host maintenance, and intermediary metabolism was studied in parenterally fed Swiss mice bearing subcutaneously implanted Lewis lung carcinoma. Non-N energy was provided from dextrose (CHO), lipid emulsion (FAT), or a 75:25 balanced (BAL) solution, infused from day 14 through day 22 postimplant. Control mice were offered equivalent energy and N from a balanced, casein-based solid diet (CAS). Tumor-doubling time was significantly prolonged in the CHO group compared to FAT and CAS. Pulmonary metastatic nodules were decreased in number in all parenterally fed mice compared to CAS, suggesting that the route of administration altered pulmonary physiology in such a way that the transmissability and/or growth of the tumor cells was inhibited. Tumor-free body weight was maintained in the CHO (+ 1.3%) and BAL (+ 0.3%) groups. However, significant weight loss occurred, despite equal intake, in the FAT (-4.7%) and CAS (-7.5%) groups. The energy appeared to be channeled into nonoxidative pathways, reflected by an increase in hepatic and adipose tissue lipogenesis and hepatic glycogen content. During the period studied, parenteral dextrose/amino acid infusion in this host-tumor system resulted in a decrease in primary tumor growth and optimal host maintenance compared to fat-based TPN and enteral feeding of a balanced, solid diet. Tumor metastasis was decreased in all parenterally fed mice, a phenomenon related to the route of administration and apparently independent of energy substrate.

The effects of glucose and amino acids on tumor and host DNA synthesis

Tumor-bearing animals provided with intravenous glucose and amino acids (TPN) exhibit enhanced response to S-phase-specific chemotherapeutic agents (H. M. Reynolds, J. M. Daly, B. Rowlands, S. J. Dudrick, and E. M. Copeland. Cancer 45: 3069, 1980; M. H. Torosian, J. L. Mullen, E. E. Miller, et al. J. Parenter. Enteral Nutr. 7: 337, 1983). To determine the mechanism of this response, DNA synthesis rate during starvation or a 48-hr infusion of glucose/amino acids (Glu/AA) was evaluated in tumor, liver, and terminal ileal cells of 68 rats. Tumor cells exhibited a rapid increase in DNA synthesis following the initiation of an infusion of Glu/AA. This increase was most marked after 2 hr of infusion and returned to control levels within 24 hr. Liver DNA synthesis rate increased in both starved and Glu/AA animals over 48 hr with a larger increase in animals receiving Glu/AA. Ileal DNA synthesis decreased equally in both groups. Short pulse Glu/AA produced transient increases in tumor DNA synthesis. Changes in host tissues occurred but followed a different temporal sequence. This may indicate the existence of a period of time following initiation of metabolic manipulation when tumor susceptibility to phase-specific chemotherapeutic agents will be enhanced while host tissues will be spared from increased toxicity.

Macronutrient requirements in the malnourished cancer patient. How much of what and why?

Malnutrition is a prevalent problem in the hospitalized cancer population. Although the pathophysiology of cancer cachexia is incompletely understood, it assumes considerable clinical relevance because malnutrition is a potentially treatable problem associated with poor outcome. Once the clinician has made a decision to initiate enteral or parenteral nutritional support, the practical issue of macronutrient prescription necessitates review of existing animal and human data in order to formulate guidelines for nonprotein energy and nitrogen requirements for efficacious nutritional support in the malnourished cancer patient.

Energy replacement during parenteral nutrition in surgery, sepsis and cancer

For many years, the increased nutritional requirements of surgical, septic and cancer patients were identified, but no effective therapy existed for averting their negative calorie and nitrogen balance. Parenteral nutrition offered an answer in many of these situations. However, abnormalities in liver function, ventilatory load, hyperglycemia and a disturbed metabolic homeostasis showed that in excessive amounts, glucose can behave as a relatively toxic substance. For cases with increased energy expenditure, new alternatives had to be devised in order to avoid excessive glucose intakes. One obvious possibility in these cases was to refrain from offering more than the basal caloric needs, until the patient had passed the period of acute injury, or other measures had effectively controlled the sepsis or cancer. Other options included the partial substitution of glucose by lipids or amino acids. Preliminary information suggests that this approach could lead to better nutritional outcome and survival rates, but additional studies are required.

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 [doxorubicin] ). 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 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 less than 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 less than 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.