Significant reduction of laparotomy-associated lung metastases and subcutaneous tumors after perioperative immunomodulation with flt3 ligand in mice

Plasma monocyte chemotactic protein-1 remains elevated after minimally invasive colorectal cancer resection

AIM: To investigate plasma Monocyte Chemotactic Protein-1 levels preoperatively in colorectal cancer (CRC) and benign patients and postoperatively after CRC resection.

METHODS: A plasma bank was screened for minimally invasive colorectal cancer resection (MICR) for CRC and benign disease (BEN) patients for whom preoperative, early postoperative, and 1 or more late postoperative samples (postoperative day 7-27) were available. Monocyte chemotactic protein-1 (MCP-1) levels (pg/mL) were determined via enzyme linked immuno-absorbent assay.

RESULTS: One hundred and two CRC and 86 BEN patients were studied. The CRC patient’s median preoperative MCP-1 level (283.1, CI: 256.0, 294.3) was higher than the BEN group level (227.5, CI: 200.2, 245.2; P = 0.0004). Vs CRC preoperative levels, elevated MCP-1 plasma levels were found on postoperative day 1 (446.3, CI: 418.0, 520.1), postoperative day 3 (342.7, CI: 320.4, 377.4), postoperative day 7-13 (326.5, CI: 299.4, 354.1), postoperative day 14-20 (361.6, CI: 287.8, 407.9), and postoperative day 21-27 (318.1, CI: 287.2, 371.6; P < 0.001 for all).

CONCLUSION: Preoperative MCP-1 levels were higher in CRC patients (vs BEN). After MICR for CRC, MCP-1 levels were elevated for 1 mo and may promote angiogenesis, cancer recurrence and metastasis.

CpG ODN, Toll like receptor (TLR)-9 agonist, inhibits metastatic colon adenocarcinoma in a murine hepatic tumor model

BACKGROUND

Colorectal liver metastases (mets) are often refractory to conventional therapies. CpG oligodeoxynucleotide 1826 (CpG), a Toll like receptor (TLR)-9 agonist, inhibits murine tumor growth by augmenting Th1 immunity. The impact of CpG on metastatic colon tumors is unknown. The purpose of this study was to determine the effect of CpG on the growth of hepatic colon cancer mets.

METHODS

Two studies with separate control groups were performed using 40 Balb/C mice (study A, CpG 50 μg/dose; study B, 100 μg/dose; n = 9-11/subgroup). Tumors were induced via portal vein injection of 2 × 10(4) CT26 colon tumor cells. After surgery, the mice were randomized; test groups were given 14 daily intraperitoneal (i.p.) CpG injections (50 or 100 μg/dose) while the control group received i.p. saline. On d 21 mice were sacrificed, the livers and spleens excised and weighed and the mets counted (reported as median ± 95% confidence interval [CI]) and histologically assessed.

RESULTS

The CpG mice had significantly fewer hepatic mets/mouse (study A, median two nodules, 95% CI, 0-3; study B, 0 nodules, 95% CI 0-0) than the control mice (study A, 6 nodules, 95% CI, 3-9, P = 0.002; Study B, 6 nodules, 95% CI, 3-9, P < 0.001). In study B, there were no mets in 9/11 CpG mice (versus 2/10 for CpG 50 μg and 0/19 for control mice). The mean liver/spleen weights of the CpG mice in both studies were significantly greater than in control mice. Histologically, high mitotic rates were noted in control mets while fewer tumor cells and histiocytic and lymphocytic infiltrates were found in CpG livers.

CONCLUSIONS

CpG inhibited liver tumor growth in this model (100 μg/dose more than 50 μg/dose). CpG was associated with increased liver and spleen weights not related to tumor burden. Increased lymphocytic and histiocytic infiltrates were noted in CpG-treated tumor nodules.

Perioperative sargramostim (recombinant human GM-CSF) induces an increase in the level of soluble VEGFR1 in colon cancer patients undergoing minimally invasive surgery

INTRODUCTION

Experimentally, laparotomy is associated with increased tumor growth. In humans, abdominal surgery is associated with immunosuppression and elevated plasma VEGF levels that might stimulate tumor growth early after surgery. Avoidance of these surgery-related changes and their consequences may be advantageous. Granulocyte-macrophage colony stimulating factor (GMCSF) is a non-specific immune system up-regulator that has also been associated, experimentally, with increased release of soluble VEGF Receptor 1 (sVEGFR1) which is an endogenous inhibitor of VEGF. This study's purpose was to determine the impact of perioperatively administered recombinant human GMCSF (rhu-GMCSF) on both immune function and plasma sVEGFR1 levels in colorectal cancer patients.

METHODS

This randomized placebo-controlled study included 36 colorectal cancer patients who underwent minimally invasive resection (17 GMCSF, 19 Placebo). Patients received 7 subcutaneous injections of either rhu-GMCSF, 125 microg/m2, or saline on preoperative days 3, 2 and 1 and on postoperative days (POD) 1, 2, 3 and 4. A number of immune parameters were followed and plasma levels of soluble VEGF Receptor 1 (sVEGFR1) and VEGF were determined.

RESULTS

The total WBC, neutrophil, eosinophil, and monocyte counts were significantly higher after surgery in the GMCSF group; no differences were noted for the other immune parameters. In the GMCSF group, median plasma sVEGFR1 levels were significantly elevated on POD 1 (188.1 pg/ml), and on POD 5 (142.8 pg/ml) when compared to pre-GMCSF levels (0 pg/ml) (p-value<0.05 for all comparisons). In the placebo group, the POD5 median sVEGFR1 level (116.3 pg/ml) was elevated and of borderline significance (p=0.05) vs the pre-treatment result (0 pg/ml). Of note, both groups had significantly elevated median plasma VEGF levels on POD 5 (Control 435.7 pg/ml; GMCSF 385.3 pg/ml) when compared to their preoperative results (Control 183.3 pg/ml, p=0.0013; GMCSF 171.5 pg/ml, p=0.0055).

CONCLUSIONS

Perioperative GMCSF was not associated with an immune function benefit in this study, however, such treatment leads to increased plasma sVEGFR1 levels. Colorectal resection, with or without GMCSF, was also associated with increased VEGF levels postoperatively. Increased plasma levels of sVEGFR1 after surgery might limit the pro-angiogenic tumor stimulatory effects of VEGF. Further study of GMCSF's impact on angiogenesis appears warranted.

Minimally invasive cancer surgery improves patient survival rates through less perioperative immunosuppression

The import of the immune system to cancer survival is paramount. Immune effector cells are intimately involved in the patient's response to cancer. People with decreased immune function develop cancer more frequently. In the early stages of solid organ malignancies, surgery can potentially be curative. Surgical intervention, in and of itself, is immunosuppressive. Surgical resections are traditionally performed through large incisions. Technologic advances have allowed minimally invasive surgery (MIS) to evolve to the point it is now being used for cancer treatment. Recent minimally invasive series have reported improved survival and recurrence rates, as compared with historical data. We hypothesized that outcome differences for cancer patients undergoing open surgery vs. MIS are due to differential inhibition of immune effector cell function, in response to the different surgical stimulus. This increased immunosuppression after open surgery could potentially inhibit immune effector cell tumor surveillance as well as inhibit scavenging of any residual or micrometastatic disease or of tumor cells shed at the time of the operation. The less immunosuppressive MIS may leave immune function above a threshold level where remaining tumor is cleared. This difference would lead to less recurrence and to survival advantages. A deeper understanding of the integral components of the immune response to surgery would open the door for immunomodulation strategies and be of great clinical utility in guiding neoadjuvant, surgical, or adjuvant therapeutic decisions.

Perioperative immunomodulation with Flt3 kinase ligand or a whole tumor cell vaccine is associated with a reduction in lung metastasis formation after laparotomy in mice

INTRODUCTION

Laparotomy has been associated with temporary postoperative immunosuppression and accelerated tumor growth in experimental models. In a previous murine study, a whole cell vaccine plus the adjuvant monophosphoryl-lipid A was shown to be effective in decreasing the number of lung metastases that develop after laparotomy. This study was conducted to assess the impact of the adjuvant fetal liver tyrosine kinase 3 (Flt3) ligand on perioperative tumor growth when used alone or with a tumor cell vaccine.

METHODS

An intravenous tumor cell injection lung metastases model was used. Sixty female A/J mice were divided into six equal groups designated (1) anesthesia control (AC), (2) AC with Flt3 ligand (ACFlt3), (3) sham laparotomy (OP), (4) OP with Flt3 ligand (OPFlt3), (5) OP with vaccine (OPVac), and (6) OP with Flt3 ligand and vaccine (OPFlt3Vac). Groups 2, 4, and 6 received daily intraperitoneal injections of Flt3 ligand (10 microg/dose with carrier) for 5 days before and 5 days after surgery. Groups 1 and 3 received similar injections of saline on the same schedule. Groups 5 and 6 were vaccinated with irradiated whole Ta3Ha tumor cells intraperitoneally three times before and twice after surgery. Immediately after surgery, all mice were injected with 10(5) Ta3Ha tumor cells via a tail vein. After 14 days, the mice were sacrificed and their lungs and tracheas were excised en bloc. Specimens were stained and counterstained with India ink and Fekete solution, and surface metastases were counted by a blinded observer. Differences between study groups were determined by analysis of variance. The peritumoral inflammatory cell infiltrate of some Flt3 and control specimens was also assessed.

RESULTS

Regarding laparotomy, Flt3 ligand (mean, 1.22 metastases), whole cell vaccine (1.12 metastases), and the combination of these two agents (0.1 metastases) were each effective in significantly decreasing the number of surface lung metastases compared with surgery alone (9.88 metastases, P < .05 for all comparisons). There were no differences between the various treatment groups in regards to number of metastases. Only the combination of Flt3 and the vaccine significantly lowered the incidence of tumors (number of mice with > or =1 tumors). Histologic analysis revealed that the Flt3-treated mice demonstrated increased numbers of antigen-presenting cells surrounding the tumors compared with controls.

CONCLUSIONS

Perioperative treatment with either Flt3 ligand or a whole cell tumor vaccine significantly reduced the number of lung metastases after laparotomy. The combination of the Flt3 ligand and the vaccine also decreased the incidence of metastases and was the most effective treatment. Further studies regarding perioperative immune modulation in the setting of cancer appear warranted.