The therapeutic use of the unconjugated monoclonal antibodies (MAb) 17-1A in combination with GM-CSF in the treatment of colorectal carcinoma (CRC)

Expression and function of epithelial cell adhesion molecule EpCAM: where are we after 40 years?

EpCAM (epithelial cell adhesion molecule) was discovered four decades ago as a tumor antigen on colorectal carcinomas. Owing to its frequent and high expression on carcinomas and their metastases, EpCAM serves as a prognostic marker, a therapeutic target, and an anchor molecule on circulating and disseminated tumor cells (CTCs/DTCs), which are considered the major source for metastatic cancer cells. Today, EpCAM is reckoned as a multi-functional transmembrane protein involved in the regulation of cell adhesion, proliferation, migration, stemness, and epithelial-to-mesenchymal transition (EMT) of carcinoma cells. To fulfill these functions, EpCAM is instrumental in intra- and intercellular signaling as a full-length molecule and following regulated intramembrane proteolysis, generating functionally active extra- and intracellular fragments. Intact EpCAM and its proteolytic fragments interact with claudins, CD44, E-cadherin, epidermal growth factor receptor (EGFR), and intracellular signaling components of the WNT and Ras/Raf pathways, respectively. This plethora of functions contributes to shaping intratumor heterogeneity and partial EMT, which are major determinants of the clinical outcome of carcinoma patients. EpCAM represents a marker for the epithelial status of primary and systemic tumor cells and emerges as a measure for the metastatic capacity of CTCs. Consequentially, EpCAM has reclaimed potential as a prognostic marker and target on primary and systemic tumor cells.

Documenting the natural history of patients with resected stage II adenocarcinoma of the colon after random assignment to adjuvant treatment with edrecolomab or observation: results from CALGB 9581

PURPOSE

We conducted a randomized trial comparing adjuvant treatment with edrecolomab versus observation in patients with resected, low-risk, stage II colon cancer. This study also prospectively studied patient- and tumor-specific markers of treatment outcome.

PATIENTS AND METHODS

After surgical resection, patients with stage II colon cancer were randomly assigned to either five infusions of edrecolomab at 28-day intervals or observation without adjuvant therapy.

RESULTS

Final accrual included 1,738 patients; 865 patients received edrecolomab, and 873 patients were observed without adjuvant treatment. Median follow-up time was 7.9 years. There were no significant outcome differences between study arms (overall survival [OS], P = .71; disease-free survival, P = .64). The combined 5-year all-cause OS was 0.86 (95% CI, 0.84 to 0.88), and the combined 5-year disease-specific OS was 0.93 (95% CI, 0.91 to 0.94). The relationships between demographic and histopathologic factors and survival differed for all-cause and disease-specific survival outcomes, but no combined prognostic factor model was found to adequately classify patients at higher risk of recurrence or death as a result of colon cancer.

CONCLUSION

Edrecolomab did not prolong survival. Consequently, this large study with a long duration of follow-up provided unique data concerning the natural history of resected stage II colon cancer. Prognostic factors identified in previous retrospective and pooled analyses were associated with survival outcomes in this stage II patient cohort. Results from ongoing molecular marker studies may enhance our ability to determine the risk profile of these patients.

Monoclonal antibody therapy for cancer

Monoclonal antibody therapy has emerged as an important therapeutic modality for cancer. Unconjugated antibodies show significant efficacy in the treatment of breast cancer, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia. Promising new targets for unconjugated antibody therapy include cellular growth factor receptors, receptors or mediators of tumor-driven angiogenesis, and B cell surface antigens other than CD20. Immunoconjugates composed of antibodies conjugated to radionuclides or toxins show efficacy in non-Hodgkin's lymphoma. One immunoconjugate containing an antibody and a chemotherapy agent exhibits clinically meaningful antitumor activity in acute myeloid leukemia. Numerous efforts to exploit the ability of antibodies to focus the activities of toxic payloads at tumor sites are under way and show early promise. The ability to create essentially human antibody structures has reduced the likelihood of host-protective immune responses that otherwise limit the duration of therapy. Antibody structures now can be readily manipulated to facilitate selective interaction with host immune effectors. Other structural manipulations that improve the selective targeting properties and rapid systemic clearance of immunoconjugates should lead to the design of effective new treatments, particularly for solid tumors.