Humanized Anti-Carcinoembryonic Antigen Antibodies Brightly Target and Label Gastric Cancer in Orthotopic Mouse Models

Bright and Specific Targeting of Metastatic Lymph Nodes in Orthotopic Mouse Models of Gastric Cancer with a Fluorescent Anti-CEA Antibody

BACKGROUND

Gastric cancer poses a major diagnostic and therapeutic challenge. Improved visualization of tumor margins and lymph node metastases with tumor-specific fluorescent markers could improve outcomes.

METHODS

To establish orthotopic models of gastric cancer, one million cells of the human gastric cancer cell line, MKN45, were suspended in 50 μl of equal parts PBS and Matrigel and injected into the nude mouse stomach with a 29-gauge needle. Tumors were allowed to grow for 8-12 weeks before performing imaging studies. For tumor labeling, M5A (humanized anti-CEA mAb) and IgG as a control, were conjugated with the near-infrared dye IRDye800CW. Mice were randomized to receive 50 μg of M5A-IR800 (n = 14) or 50 μg of IgG-IR800 (n = 14) intravenously and were imaged 72 hours later. Fluorescence imaging was performed using the LI-COR Pearl Imaging System.

RESULTS

Forty-two lymph nodes were collected from 28 mice, of which 59.5% were found to contain metastatic gastric cancer cells on pathologic examination. In mice that received M5A-IR800, there was a statistically significant difference in the mean fluorescence signal for cancer-positive lymph nodes at 0.431 (SE ± 0.224) compared with 0.105 (SE ± 0.009) for cancer-negative nodes (p: 0.002). For IgG-IR800, there was no significant difference in the mean fluorescence signal for cancer-positive nodes (0.057) compared with cancer-negative nodes (0.064), p-value 0.677.

CONCLUSIONS

Humanized anti-CEA (M5A) antibodies conjugated to fluorescent dyes provide bright labeling of lymph nodes containing metastatic gastric cancer. This tumor-specific fluorescent antibody is a promising clinical tool for identifying lymph nodes containing metastatic gastric cancer.

A new locoregional mouse model of gastric cancer for identifying probes for fluorescence guided surgery

BACKGROUND

In gastric cancer, the only opportunity for a cure is with surgical resection. Fluorescence-guided surgery is an emerging field that has the potential to improve rates of R0 resections. Mouse models with patterns of disease spread that would be deemed operable in patients are required for the testing of potential fluorescence-guided surgery probes.

METHODS

One million cells of the human gastric cancer cell line MKN45 were suspended in 50 μL of phosphate-buffered saline and Matrigel and injected into the mouse stomach with a 29-gauge needle. After 8 to 12 weeks of tumor growth, mice were killed and laparotomy was performed to determine rates of tumor engraftment, local or distant spread, and involvement of celiac lymph nodes. For tumor labeling, mice were randomized to receive intravenous injection of an anti-CEA antibody (M5A), or IgG as a control, conjugated with the near-infrared dye IRDye800CW. Fluorescence imaging was performed using the LI-COR Pearl Imaging System 72 hours later.

RESULTS

Infiltrative tumors were identified in 76.5% (n = 34) of mice. Intra-abdominal or peritoneal metastases were seen in 23.5% and carcinomatosis was seen in 5.9% of mice. Celiac lymph node metastases were seen in 55.5% of mice. M5A-IR800 administration resulted in bright labeling of primary tumors and metastatic celiac lymph nodes. Hematoxylin and eosin staining demonstrated incorporation of the gastric cancer cells throughout the layers of the mouse stomach and the presence of metastatic gastric cancer cells in celiac lymph nodes.

CONCLUSION

This new locoregional mouse model can be used to validate additional agents for their use in fluorescence guided surgical resection of gastric cancer.

Potential Probes for Targeted Intraoperative Fluorescence Imaging in Gastric Cancer

Gastric cancer (GC) is a malignant tumor of the gastrointestinal tract associated with high mortality rates and accounting for approximately 1 million new cases diagnosed annually. Surgery, particularly radical gastrectomy, remains the primary treatment; however, there are currently no specific approaches to better distinguish malignant from healthy tissue or to differentiate between metastatic and non-metastatic lymph nodes. As a result, surgeons have to remove all lymph nodes indiscriminately, increasing intraoperative risks for patients and prolonging hospital stay. Near-infrared fluorescence imaging with indocyanine green (ICG) can provide real-time visualization of the surgical field using both conventional laparoscopy and robotic mini-invasive precision surgery platforms. However, its application shows some limits, as ICG is a non-targeted contrast agent. Several studies are now investigating the potential efficacy of fluorescent targeted agents that could selectively bind to the tumor tissue, offering a valuable tool for metastatic mapping during robotic gastrectomy. This review aims to summarize the key fluorescent agents that have been developed to recognize GC markers, as well as those targeting the tumor microenvironment (TME) and metabolic features. These agents hold great potential as valuable tools for enhancing precision surgery in robotic gastrectomy procedures improving the clinical recovery of GC patients.

Targeting Patient-Derived Orthotopic Gastric Cancers with a Fluorescent Humanized Anti-CEA Antibody

BACKGROUND

Gastric cancer poses a major diagnostic and therapeutic challenge as surgical resection provides the only opportunity for a cure. Specific labeling of gastric cancer could distinguish resectable and nonresectable disease and facilitate an R0 resection, which could improve survival.

METHODS

Two patient-derived gastric cancer lines, KG8 and KG10, were established from surgical specimens of two patients who underwent gastrectomy for gastric adenocarcinoma. Harvested tumor fragments were implanted into the greater curvature of the stomach to establish patient-derived orthotopic xenograft (PDOX) models. M5A (humanized anti-CEA antibody) or IgG control antibodies were conjugated with the near-infrared dye IRDye800CW. Mice received 50 µg of M5A-IR800 or 50 µg of IgG-IR800 intravenously and were imaged after 72 hr. Fluorescence imaging was performed by using the LI-COR Pearl Imaging System. A tumor-to-background ratio (TBR) was calculated by dividing the mean fluorescence intensity of the tumor versus adjacent stomach tissue.

RESULTS

M5A-IR800 administration resulted in bright labeling of both KG8 and K10 tumors. In the KG8 PDOX models, the TBR for M5A-IR800 was 5.85 (SE ± 1.64) compared with IgG-IR800 at 0.70 (SE ± 0.17). The K10 PDOX models had a TBR of 3.71 (SE ± 0.73) for M5A-IR800 compared with 0.66 (SE ± 0.12) for IgG-IR800.

CONCLUSIONS

Humanized anti-CEA (M5A) antibodies conjugated to fluorescent dyes provide bright and specific labeling of gastric cancer PDOX models. This tumor-specific fluorescent antibody is a promising potential clinical tool to detect the extent of disease for the determination of resectability as well as to visualize tumor margins during gastric cancer resection.

Current status and future trends of real-time imaging in gastric cancer surgery: A literature review

Technological advances are crucial for the optimization of gastric cancer surgery, and the success of any gastric cancer surgery is based on the correct and precise anatomical determination of the primary tumour and tissue structures. Real-time imaging-guided surgery is showing increasing potential and utility, mainly because it helps to aid intraoperative decision-making. However, intraoperative imaging faces many challenges in the field of gastric cancer. This article summarizes and discusses the following clinical applications of real-time optical imaging and fluorescence-guided surgery for gastric cancer: (1) the potential of quantitative fluorescence imaging in assessing tissue perfusion, (2) vascular navigation and determination of tumour margins, (3) the advantages and limitations of lymph node drainage assessment, and (4) identification of peritoneal metastases. In addition, preclinical study of tumour-targeted fluorescence imaging are discussed.