The impact of surgical extent and sex on the hepatic metastasis of colon cancer

Purpose

Extensive oncological surgeries were previously suggested to increase cancer recurrence rates. We herein studied the impact of different surgical procedures and sex on colorectal cancer liver metastasis, employing several tumor inoculation approaches in BALB/c mice.

Methods

Experimental hepatic metastases of the syngeneic CT26 colorectal cancer line were induced either by intra-portal inoculation or intra-splenic inoculation, employing different tumor loads. Following intra-splenic inoculation, the entire spleen or an injected hemi-spleen was removed. Additionally, the magnitude of the surgical trauma accompanying the injection procedure was manipulated.

Results

Increasing the surgical trauma by adding laparotomy or extending the length of the surgery and hypothermia did not significantly affect the number of liver metastases or liver weight for any of the injection methods and tumor loads. The development of metastasis was significantly greater in males than in females under all conditions studied—a difference not explained by the direct effects of sex hormones on in vitro CT26 proliferation or vitality.

Conclusion

Concurring with less controlled clinical observations, the surgical extensiveness did not significantly affect CT26 hepatic metastasis, potentially due to a ceiling effect of the surgical trauma on the metastatic process. The sexual dimorphism observed for the CT26 metastasis should be investigated in the context of surgical stress and considering anti-CT26 immunoreactivity.     

Evidence that postoperative pain is a mediator of the tumor-promoting effects of surgery in rats

We have previously shown in rats that the provision of analgesic doses of morphine significantly reduces the tumor-promoting effects of undergoing and recovering from surgery. Because morphine had no effect in non-operated animals, and because a single preoperative dose given hours before tumor inoculation was effective, we have suggested that it is the pain-relieving effects of the drug that underlies its beneficial impact. To support and strengthen this suggestion, two different regimens of analgesia were employed, the systemic administration of the more selective mu-agonist, fentanyl, and the intrathecal (i.t.) administration of bupivacaine plus morphine. To assess host resistance against metastasis, we used a lung clearance assay of the MADB106 mammary adenocarcinoma, a natural killer (NK)-sensitive syngeneic cell line that metastasizes only to the lungs. Female and male Fischer 344 rats were randomly assigned to one of four groups using a 2x2 experimental design: experimental laparotomy under halothane anesthesia versus anesthesia alone, by drug treatment versus vehicle. In the first in vivo experiment, fentanyl was administered 20 min before surgery (40 microg/kg subcutaneously (s.c.)), and at the end of surgery in a slow-release suspension (20 microg/kg s.c.). In the second in vivo experiment, bupivacaine (10 microg) plus morphine (20 microg) in 50 microl was administered i.t. before surgery. Surgery resulted in a 3- to 4-fold increase in the lung retention of MADB106 cells in both males and females, and the observed surgery-induced increase in lung tumor retention was reduced by more than 65% in the fentanyl-treated animals and more than 45% in the animals receiving i.t. bupivacaine plus morphine. Neither drug regimen exerted effects in the anesthesia only animals. Surgery also resulted in a significant suppression of whole blood NK activity assessed at 5 h postoperatively, the same time point at which MADB106 tumor cells were inoculated in the in vivo studies. Unlike the in vivo study, fentanyl suppressed NK activity at this time point in non-operated rats, but had no effect in operated rats. Taken together, these findings strengthen the suggestion that the management of perioperative pain is a critical factor in preventing surgery-induced decreases in host resistance against metastasis. If similar relationships between pain and metastasis occur in humans, then pain control must become a priority in the postoperative care of individuals with cancer.     

Prostaglandin E<Subscript>2</Subscript> Suppresses NK Activity In Vivo and Promotes Postoperative Tumor Metastasis in Rats

Background: Prostaglandins (PGs) were shown in vitro to suppress several functions of cellular immunity. It is unclear, however, whether physiological levels of PGs can suppress cellular immunity in vivo and whether such suppression would compromise postoperative host resistance to metastasis.Methods: Fischer 344 rats were administered PGE₂ in doses (18 to 300 g/kg subcutaneously) that increased the serum levels approximately 2- to 4-fold. We then assessed the number and activity of circulating natural killer (NK) cells, as well as rats resistance to experimental metastasis of a syngeneic NK-sensitive tumor (MADB106). To study whether endogenously released PGs after surgery compromise these indices, we tested whether laparotomy adversely affects them and whether a cyclooxygenase-synthesis inhibitor, indomethacin (4 mg/kg), attenuates these effects.Results: PGE₂ dose-dependently suppressed NK activity per NK cell and dose-dependently increased 4- and 24-hour MADB106 lung tumor retention (LTR); 240 g/kg of PGE₂ quadrupled the number of lung metastases counted 3 weeks later. Selective depletion of NK cells abrogated the promotion of LTR by PGE₂. Surgery significantly suppressed NK activity and increased MADB106 LTR, and indomethacin halved these effects without affecting nonoperated rats.Conclusions:PGE₂ is a potent in vivo suppressor of NK activity, and its postoperative release may promote tumor recurrence.     

Timing within the oestrous cycle modulates adrenergic suppression of NK activity and resistance to metastasis: possible clinical implications

Clinical observations suggest that the rate of metastatic development and long-term mortality following surgery in breast cancer patients is influenced by the menstrual phase during which surgery is conducted. The menstrual cycle is known to modulate various physiological responses and medical conditions that involve adrenergic mechanisms (e.g., asthma). Natural killer activity (NKA), an immune function controlling metastasis, is suppressed following surgery, and in vitro by adrenaline. We therefore hypothesize that the clinical observation may be partly attributable to surgery-induced adrenergic suppression of NK-dependent resistance to metastasis, a suppression that depends on menstrual phase during surgery. To test this hypothesis in rats, 140 F344 females at different phases of their oestrous cycle were injected with a beta-adrenergic agonist, metaproterenol (MP) (0.4 or 0.8 mg kg(-1), s.c.), or with vehicle, before i.v. inoculation with MADB106 tumour cells. This syngeneic mammary adenocarcinoma line metastasizes only to the lungs, and is highly sensitive to NKA. In a second experiment, the suppression of NKA by MP was studied in vitro in blood drawn at different phases of the oestrous cycle (n = 36). Finally, the effects of stress on the number and activity of NK cells were assessed along the oestrous cycle (n = 71). The findings indicate that the suppressive effects of MP on resistance to metastasis and on NKA, are significantly greater during the oestrous phase characterized by high oestradiol levels (D3/proestrus/oestrus). Similarly, NKA per cell was suppressed by stress only during this phase. In untreated animals, in which inadvertent stress was minimized, no effects of the oestrous cycle on NKA or on resistance to metastasis were evident. These findings indicate that the oestrous cycle modulates adrenergic suppression of NKA and of resistance to metastasis. The relevance of these findings to the above clinical observation, as well as that of our related findings in women from a parallel study, is discussed.     

Poly I-C induces early embryo loss in f344 rats: a potential role for NK cells

PROBLEM: Natural killer (NK) cells were associated with first trimester embryo loss. The current study in the inbred F344 rat assessed the role of NK cells in mediating resorptions caused by poly I-C, a non-specific immunostimulator. METHOD OF STUDY: On fifth day of gestation, rats were injected intraperitoneally with anti-NKR-P1 (1.5 mg/kg, i.p.) to deplete NK cells, and with mouse serum or saline to control for non-specific effects. Poly I-C (4 mg/kg, i.p.) or vehicle were administered 2 days later. Resorptions were assessed on day 13.5. RESULTS: Poly I-C significantly elevated resorption rates, and anti-NKR-P1 abolished this effect. Body weight was reduced in all rats treated with poly I-C, including NK-depleted rats. This indicates the ability of NK-depleted rats to respond to poly I-C, yet to refrain from the resorption-promoting effects of poly I-C. CONCLUSIONS: This study suggests a role for NK cells in mediating poly I-C-induced resorptions.     

The effects of a Chinese herb formula, anti-cancer number one (ACNO), on NK cell activity and tumor metastasis in rats

The effects of anti-cancer number one (ACNO), a 19-herb Chinese formula used to treat cancer patients, were studied in F344 rats. In the first study, the number and activity of circulating NK cells were evaluated following 18 days of oral consumption of 0.1, 0.5, or 2 g/kg/day. The second study assessed the effect of ACNO on resistance to metastasis of the MADB106 tumor line, a syngeneic mammary adenocarcinoma that metastasizes only to the lungs and is highly sensitive to NK activity (NKA) in vivo. Resistance to metastasis was assessed under baseline conditions and following the administration of a beta-adrenergic agonist, metaproterenol (MP). MP was used to simulate sympathetic response to stressful conditions, and was previously shown to suppress resistance to MADB 106 metastasis. The results of the first study indicated a dose-dependent increase in NKA per ml of blood and per NK cell, with no significant changes in blood concentration of NK cells. In the second study, whereas MP caused a 4.5-fold increase in the number of metastases in untreated rats, only a 2.3-fold increase occurred in rats treated with ACNO. No significant improvement in baseline levels of resistance to metastasis was observed. These findings indicate the importance of studying ACNO under stressful conditions in patients with potentially metastasizing tumors. This may prove particularly important during the perioperative period, spanning from the detection of the primary tumor to postoperative treatment. During this critical period, psychological and physiological stress responses are known to cause massive immunosuppression, which was suggested to promote metastatic development.     

Thermographic imaging of pathoneurophysiology due to cervical disc herniation

A patient suffering from cervical disc herniation as noted by magnetic resonance imaging was tested for presence of nerve irritation using infrared telethermography. The thermal findings and asymmetries observed followed a dermatomal pattern of hypothermia and decreased thermal emission. The neurophysiological information derived from the thermographic examination may be helpful in the diagnosis and management of cervical disc herniations encountered in clinical practice.     

Stimulation of the hypothalamic paraventricular nucleus produces analgesia not mediated by vasopressin or endogenous opioids

The analgesic effect of electrical stimulation of the hypothalamic paraventricular nucleus (PVN) was studied. Additionally, the involvement of vasopressin and opioid peptides in this process was examined by comparing vasopressin-deficient (Brattleboro) and Long-Evans rats and by administering the opiate antagonist naloxone. Rats were chronically implanted with a stimulating electrode in the parvocellular (PVN-Pc) and magnocellular (PVN-Mg) divisions of the PVN. At least 10 days after surgery, the analgesic effects of PVN stimulation were examined in lightly anesthetized rats, using the tail-flick method, and in unanesthetized rats, using the hot-plate test. PVN stimulation produced marked analgesia in both tests. Current threshold for analgesia was lower from PVN-Pc than from PVN-Mg. Threshold did not differ significantly between Brattleboro and Long-Evans rats and was not affected by naloxone administration. The results indicate that the PVN is part of the brain's pain inhibitory system, and show that the analgesia induced by PVN stimulation is not mediated by either vasopressin or opioid peptides.