Minimal residual disease: detection, clinical relevance, and treatment strategies

Defining the "Metastasome": Perspectives from the genome and molecular landscape in colorectal cancer for metastasis evolution and clinical consequences

Metastasis still poses the highest challenge for personalized therapy in cancer, partly due to a still incomplete understanding of its molecular evolution. We recently presented the most comprehensive whole-genome study of colorectal metastasis vs. matched primary tumors and suggested novel components of disease progression and metastasis evolution, some of them potentially relevant for targeted therapy. In this review, we try to put these findings into perspective with latest discoveries of colleagues and recent literature, and propose a systematic international team effort to collectively define the "metastasome", a term we introduce to summarize all genomic, epigenomic, transcriptomic, further -omic, molecular and functional characteristics rendering metastases different from primary tumors. Based on recent discoveries, we propose a revised metastasis model for colorectal cancer which is based on a common ancestor clone, early dissemination but flexible early or late stage clonal separation paralleling stromal interactions. Furthermore, we discuss hypotheses on site-specific metastasis, colorectal cancer progression, metastasis-targeted diagnosis and therapy, and metastasis prevention based on latest metastasome data.

Efficient inhibition of human B-cell lymphoma in SCID mice by synergistic antitumor effect of human 4-1BB ligand/anti-CD20 fusion proteins and anti-CD3/anti-CD20 diabodies

Here we constructed and produced a recombinant human 4-1BB ligand (4-1BBL)/anti-CD20 fusion protein and examined its antitumor activity, alone and in combination with an anti-CD3/anti-CD20 bispecific diabody. The 4-1BBL/anti-CD20 fusion protein retained both the costimulatory activity of 4-1BBL on T cells and the tumor targeting ability of CD20 antibody on B cells. The fusion protein bound as efficiently to 4-1BB- and CD20-positive cells as its respective parental antibodies, and was capable of cross-linking human T lymphocytes and CD20-positive tumor cells. Combination treatment with 4-1BBL/anti-CD20 fusion protein and anti-CD3/anti-CD20 diabody led to significantly increased T-cell cytotoxicity to human B-lymphoma cells in vitro and drastically more potent tumor inhibitory activity in vivo in xenografted B-cell lymphoma in severe combined immunodeficiency disease mice. Mechanistic studies revealed that the combination treatment remarkably inhibited apoptosis of human peripheral blood lymphocytes, accompanied by upregulation of Bcl-XL and Bf1-1, perforin and granzyme B mRNA, and increased interleukin-2 production. Taken together, these results suggest that targeted delivery of 4-1BBL to the tumor site, when combined with anti-CD3/anti-CD20 diabody, could strongly potentiate the antitumor activity of the diabody, thus may have significant clinical application in the treatment of human CD20-positive B-cell malignancies.

Combination of high-dose chemotherapy and monoclonal antibody in breast-cancer patients: a pilot trial to monitor treatment effects on disseminated tumor cells

BACKGROUND

Tumor relapse occurring in high-risk breast cancer patients after high-dose chemotherapy (HDC) and autologous stem-cell transplantation may arise from cells resistant to chemotherapy, as well as from tumor cells reinfused with autologous stem cell grafts. This pilot study was designed to investigate whether ex vivo immunomagnetic purging of PBSC and subsequent immunotherapy with MAb 17-1A is feasible and can reduce the number of disseminated tumor cells in BM.

METHODS

Twelve high-risk breast-cancer patients, seven in Stage II/III and five in Stage IV (UICC breast cancer classification) underwent surgery of the primary tumor and received two cycles of induction chemotherapy, followed by HDC. After each cycle of induction chemotherapy PBSC were collected and incubated with Ab-coated immunomagnetic beads, to remove contaminating tumor cells. Prepared stem-cell grafts were transplanted 24 h after completion of HDC. After recovering from HDC all 12 patients received a total dose of 900 mg MAb 17-1A within 4 months. The effect of in vivo purging with MAb 17-1A after HDC was controlled by examining bone aspirates of the patients with an immunocytochemical assay, allowing the detection of one cytokeratin-positive tumor cell in 10(6) total nucleated cells (TNC).

RESULTS

Tumor cells were found in 5/12 BM aspirates prior to chemotherapy and even after HDC. Further monitoring of BM aspirates for cancer cells during Ab therapy showed a consistent reduction of tumor cells in four out of these five patients. After a median clinical follow-up of 41 (32-48) months all four patients are alive. These results are different from those of a historical control group of six patients with breast cancer treated with the same chemotherapy schedule, but without 17/1A consolidation. In comparison with the patients from the study group, all patients of this control group revealed a significantly increased number of tumor cells in BM (p < 0.01) after HDC during follow-up of 5 (3-7) months. These preliminary results indicate that induction chemotherapy, followed by HDC, may reduce disseminated tumor cells in BM.

DISCUSSION

Immunotherapy with MAb 17-1A after HDC may further eliminate residual disease without severe toxicity.

Minimal residual disease in gastrointestinal cancer

Tumor progression after curative resection of gastrointestinal carcinomas is probably caused by pre- or intraoperative tumor cell dissemination. Disseminated tumor cells are generally detected by immunohistochemistry- or PCR-based molecular-biology methods. A consensus on which is the most adequate detection method has not yet been found, which makes the comparison of data difficult. The prognostic relevance of disseminated cells has been shown, at least in part, for esophageal, gastric, pancreatic, and colonic cancer. The data regarding hepatocellular cancer is conflicting. This article gives a critical review of tumor cell detection in gastrointestinal cancer.