Micrometastasis detection and treatment with monoclonal antibodies

Dendritic Cells and Cancer Immunotherapy: The Adjuvant Effect

Dendritic cells (DCs) are immune specialized cells playing a critical role in promoting immune response against antigens, and may represent important targets for therapeutic interventions in cancer. DCs can be stimulated ex vivo with pro-inflammatory molecules and loaded with tumor-specific antigen(s). Protocols describing the specific details of DCs vaccination manufacturing vary widely, but regardless of the employed protocol, the DCs vaccination safety and its ability to induce antitumor responses is clearly established. Many years of studies have focused on the ability of DCs to provide overall survival benefits at least for a selection of cancer patients. Lessons learned from early trials lead to the hypothesis that, to improve the efficacy of DCs-based immunotherapy, this should be combined with other treatments. Thus, the vaccine’s ultimate role may lie in the combinatorial approaches of DCs-based immunotherapy with chemotherapy and radiotherapy, more than in monotherapy. In this review, we address some key questions regarding the integration of DCs vaccination with multimodality therapy approaches for cancer treatment paradigms.

Tumor resistance

It is suggested that evolution has equipped humans and other species with powerful and, largely non-immunological resistance mechanisms that can nip pre-neoplastic cells, as well as cells disseminating from established tumors in the bud. These mechanisms must operate while maintaining tissue structure, polarity and a large variety of cell-to-cell interactions. Altogether, they are essential for microenvironmental tissue integrity. It has further been postulated that the genes underpinning microenvironmental control are not merely alleles of known cancer susceptibility genes, but constitute sui generis systems.

Nanomedical detection and downstream analysis of circulating tumor cells in head and neck patients

The establishment of novel biomarkers in liquid biopsies of cancer patients has come more into focus in prognostic and diagnostic research efforts. Due to their prognostic relevance disseminated tumor cells or circulating tumor cells are the subject of intensive research and are discussed as early diagnostic indicators for treatment failure and the formation of micrometastases. A potential association of this early-systemic tumor component with poor prognosis of cancer patients could be already demonstrated for various entities including breast, colon, lung, melanoma, ovarian and prostate cancers. Thus, the detection of circulating tumor cells seems to be also applicable for minimal-invasive monitoring of therapy progress in head and neck cancer patients. A major problem of the use in clinical routine is that circulating tumor cells could not be detected by modern imaging techniques. To overcome these limitations highly sensitive detection methods and techniques for their molecular characterization are urgently needed allowing mechanistic understanding and targeting of circulating tumor cells. Especially the medical application of nanotechnology (nanomedical methods) has made valuable contributions to the field. Here, we want to provide a comprehensive overview on (nanomedical) detection methods for circulating tumor cells and discuss their merits, pitfalls and future perspectives especially for head and neck solid squamous cell carcinoma (HNSCC) patients.

Dendritic Cell Cancer Therapy: Vaccinating the Right Patient at the Right Time

Immune checkpoint inhibitors propelled the field of oncology with clinical responses in many different tumor types. Superior overall survival over chemotherapy has been reported in various metastatic cancers. Furthermore, prolonged disease-free and overall survival have been reported in the adjuvant treatment of stage III melanoma. Unfortunately, a substantial portion of patients do not obtain a durable response. Therefore, additional strategies for the treatment of cancer are still warranted. One of the numerous options is dendritic cell vaccination, which employs the central role of dendritic cells in activating the innate and adaptive immune system. Over the years, dendritic cell vaccination was shown to be able to induce an immunologic response, to increase the number of tumor infiltrating lymphocytes and to provide overall survival benefit for at least a selection of patients in phase II studies. However, with the success of immune checkpoint inhibition in several malignancies and considering the plethora of other treatment modalities being developed, it is of utmost importance to delineate the position of dendritic cell therapy in the treatment landscape of cancer. In this review, we address some key questions regarding the integration of dendritic cell vaccination in future cancer treatment paradigms.

Involvement of CXCR4 chemokine receptor in metastastic HER2-positive esophageal cancer

A functional linkage of the structurally unrelated receptors HER2 and CXCR4 has been suggested for breast cancer but has not been evaluated for esophageal carcinoma. The inhibition of HER2 leads to a reduction of primary tumor growth and metastases in an orthotopic model of esophageal carcinoma. The chemokine receptor CXCR4 has been implicated in metastatic dissemination of various tumors and correlates with poor survival in esophageal carcinoma. The aim of this study was to investigate a correlation between the expression levels of HER2 and CXCR4 and to evaluate the involvement of CXCR4-expression in HER2-positive esophageal carcinoma. The effects of HER2-inhibition with trastuzumab and of CXCR4-inhibition with AMD3100 on primary tumor growth, metastatic homing, and receptor expression were evaluated in vitro and in an orthotopic model of metastatic esophageal carcinoma using MRI for imaging. The clinical relevance of HER2- and CXCR4-expression was examined in esophageal carcinoma patients. A significant correlation of HER2- and CXCR4-expression in primary tumor and metastases exists in the orthotopic model. Trastuzumab and AMD3100 treatment led to a significant reduction of primary tumor growth, metastases and micrometastases. HER2-expression was significantly elevated under AMD3100 treatment in the primary tumor and particularly in the metastases. The positive correlation between HER2- and CXCR4-expression was validated in esophageal cancer patients. The correlation of CXCR4- and HER2-expression and the elevation of HER2-expression and reduction of metastases through CXCR4-inhibition suggest a possible functional linkage and a role in tumor dissemination in HER2-positive esophageal carcinoma.

Clinical relevance associated to the analysis of circulating tumour cells in patients with solid tumours

The distant growth of tumour cells escaping from primary tumours, a process termed metastasis, represents the leading cause of death among patients affected by malignant neoplasias from breast and colon. During the metastasis process, cancer cells liberated from primary tumour tissue, also termed circulating tumour cells (CTCs), travel through the circulatory and/or lymphatic systems to reach distant organs. The early detection and the genotypic and phenotypic characterisation of such CTCs could represent a powerful diagnostic tool of the disease, and could also be considered an important predictive and prognostic marker of disease progression and treatment response. In this article we discuss the potential relevance in the clinic of monitoring CTCs from patients suffering from solid epithelial tumours, with emphasis on the impact of such analyses as a predictive marker for treatment response.

Cellular image analysis and imaging by flow cytometry

Imaging flow cytometry combines the statistical power and fluorescence sensitivity of standard flow cytometry with the spatial resolution and quantitative morphology of digital microscopy. The technique is a good fit for clinical applications by providing a convenient means for imaging and analyzing cells directly in bodily fluids. Examples are provided of the discrimination of cancerous from normal mammary epithelial cells and the high-throughput quantitation of fluorescence in situ hybridization (FISH) probes in human peripheral blood mononuclear cells. The FISH application will be enhanced further by the integration of extended depth-of-field imaging technology with the current optical system.

Ep-CAM expression in squamous cell carcinoma of the esophagus: a potential therapeutic target and prognostic marker

BACKGROUND

To evaluate the expression and test the clinical significance of the epithelial cellular adhesion molecule (Ep-CAM) in esophageal squamous cell carcinoma (SCC) to check the suitability of esophageal SCC patients for Ep-CAM directed targeted therapies.

METHODS

The Ep-CAM expression was immunohistochemically investigated in 70 primary esophageal SCCs using the monoclonal antibody Ber-EP4. For the interpretation of the staining results, we used a standardized scoring system ranging from 0 to 3+. The survival analysis was calculated from 53 patients without distant metastasis, with R0 resection and at least 2 months of clinical follow-up.

RESULTS

Ep-CAM neo-expression was observed in 79% of the tumors with three expression levels, 1+ (26%), 2+ (11%) and 3+ (41%). Heterogeneous expression was observed at all expression levels. Interestingly, tumors with 3+ Ep-CAM expression conferred a significantly decreased median relapse-free survival period (log rank, p = 0.0001) and median overall survival (log rank, p = 0.0003). Multivariate survival analysis disclosed Ep-CAM 3+ expression as independent prognostic factor.

CONCLUSION

Our results suggest Ep-CAM as an attractive molecule for targeted therapy in esophageal SCC. Considering the discontenting results of the current adjuvant concepts for esophageal SCC patients, Ep-CAM might provide a promising target for an adjuvant immunotherapeutic intervention.

Screening and identification of differentially expressed transcripts in circulating cells of prostate cancer patients using suppression subtractive hybridization

BACKGROUND

Tumor metastasis and changes in host immunosurveillance are important components in cancer development. Tumor cell invasion into the bloodstream is an essential step for systemic metastasis. Currently, the detection of tumor cells in the circulation is mainly dependent upon the utilization of known epithelial cell markers. However, expression of these molecules is not limited to cancer patients; healthy people also have a small number of epithelial cells in their circulation. Utilizing these markers to detect circulating tumor cells (CTCs) cannot adequately explain the mechanisms of tumor cell survival or their development of metastatic potential in peripheral blood. The immune system can also evolve along with the cancer, actually promoting or selecting the outgrowth of tumor variants. Unfortunately, both metastasis and immunosurveillance remain mysterious and are debatable because we have yet to define the molecules that participate in these processes. We are interested in identifying the existence of expressed genes, or mRNA species, that are specifically associated with circulating cells of cancer-bearing patients using prostate cancer (PCa) as a model.

RESULTS

We established two comprehensive subtracted cDNA libraries using a molecular technique called suppression subtractive hybridization. This technique selectively amplifies transcripts that are specifically expressed in circulating cells of either PCa patients or healthy men. Following sequencing reaction, we showed that 17 out of 23 (73.9%) sequenced clones did not match any mRNAs in the GenBank database. This result suggests that genes associated with alterations in circulating cells of cancer-bearing patients are largely unknown. Semi-quantitative RT-PCR confirmed that two genes are up-regulated in circulating cells of PCa patients, whereas another two genes are down-regulated in the same patients.

CONCLUSION

The comprehensive gene expression analysis is capable of identifying differentially expressed genes in circulating cells of healthy men and PCa patients. We did not attempt to enrich specific cell types in this study because phenotypes of CTCs and subsets of leukocytes participating in immunosurveillance remain largely unknown. Continuous studies of these differentially expressed genes will eventually lead us to understand the mechanisms involved in tumor metastasis and immune modulation during cancer development.

Real-time observation of micrometastasis formation in the living mouse liver using a green fluorescent protein gene-tagged rat tongue carcinoma cell line

Initial arrest, attachment, extravasation and subsequent extravascular growth of tumor cells in the secondary organs are believed to be crucial events for hematogenous metastasis, but the actual processes in living animals remain unclear. For the present study, we established green fluorescent protein (GFP)-expressing rat tongue carcinoma cell lines (RSC3) that permit real-time analysis of micrometastasis formation in combination with intravital video microscopy (IVVM). With this system, GFP-expressing metastatic (LM-EGFP) and non-metastatic (E2-EGFP) cell lines could be visualized at the cellular level in live mice for more than 1 month. Real-time IVVM analysis of liver metastases after intraportal injection of cells via a mesenteric vein revealed that both LM-EGFP and E2-EGFP tumor cells arrest similarly in sinusoidal vessels near terminal portal venules within 0.4 sec, during which time no evidence of a "rolling"-like movement along endothelial cell surfaces was observed. Quantitative analysis of GFP-positive foci showed that E2-EGFP cells were completely sheared from the liver sinusoid within 3 days, with no solitary dormant cells, whereas a substantial number of LM-EGFP cells remained in the liver, probably due to stable attachment to the sinusoidal wall. Confocal laser scanning microscopic study in combination with laminin immunohistochemistry revealed that only LM-EGFP cells started growth at 3 to 4 days after inoculation and that most of the growing foci were surrounded by subsinusoidal basement membrane. Our results suggest that micrometastasis formation by LM-EGFP cells consists of initial tumor cell arrest due to size constraints of the vessel, stable attachment to subsinusoidal basement membrane and subsequent intravascular growth before extravasation. The difference in metastatic potential between the 2 lines may reside in their capacity to attach stably to the vessel wall rather than their potential for initial cell arrest or subsequent growth. The system used in the present study may be a powerful tool for analyzing targets for various anti-metastatic agents in the sequential process of metastasis.

The fate and prognostic value of occult metastatic cells in the bone marrow of patients with breast carcinoma between primary treatment and recurrence

BACKGROUND

The current study examines the fate of occult metastatic cells detected in bone marrow (BM) at primary diagnosis and evaluates whether persistently positive findings support the prognostic influence of these cells in patients with Stage I--III (International Union Against Cancer) breast carcinoma.

METHODS

The authors analyzed BM aspirates, at the time of primary diagnosis and after a median interval of 19 months (range, 7--67 months), from 89 patients who were free of recurrence. The presence of cytokeratin (CK) positive cells was assessed with the monoclonal anti-CK antibody A45-B/B3. Patients were observed prospectively for a median of 41 (range, 12--78) months after the first aspiration.

RESULTS

At the time of primary diagnosis, 24 of 89 patients (27%) presented with occult metastatic cells in the BM. Of the same 89 patients, 25 (28%) had a positive BM finding at the time of the second BM analysis. Among those patients with an initially negative BM finding, 15 patients (17%) had occult metastatic cells at time of the second BM aspiration, whereas 10 patients (11%) had a persistently positive BM finding. Patients with a persistently negative BM status (n = 50) had a significantly better overall survival than patients with a positive BM status at the time of the second BM aspiration (n = 25), both by univariate analysis (P = 0.045, log-rank) and multivariate analysis (P = 0.034, Cox regression).

CONCLUSIONS

In many patients with primary breast carcinoma, minimal residual disease can be detected by follow-up examination of the BM. This finding is prognostically relevant and provides reason to include BM monitoring in future clinical trials.

Detection and relevance of immunohistochemically identifiable tumor cells in lymph nodes

Lymph node metastasis is a well-known feature of poor prognosis in potentially resectable solid epithelial tumors. However, a significant number of apparently lymph node negative patients die early of metastatic disease. Therefore, it has to be assumed that in some patients an early tumor cell dissemination has occurred which is clearly underestimated by current staging procedures. Recently, it has been shown, that an early dissemination of individual carcinoma cells to regional lymph nodes can be detected by using sensitive immunocytochemical techniques with monoclonal antibodies against epithelium-specific proteins. The incidence of immunohistochemically positive patients varies between 12% and 70% depending on the type of primary tumor, the immunohistochemical staining procedure used, and especially on the primary monoclonal antibody. The detection of disseminated tumor cells in lymph nodes by immunocytochemistry is associated with a poorer prognosis in different types of epithelial tumors such as lung cancer or esophageal cancer. The immunocytochemical method might also be useful in the detection of occult tumor cells in sentinel lymph nodes. In conclusion, the immunohistochemical detection of disseminated tumor cells in lymph nodes can help to obtain a more exact identification of patients with an unfavorable prognosis. Whether the identified patients will gain from an adjuvant therapy has to be evaluated in further studies.

Clinical relevance of occult metastatic cells in the bone marrow of patients with different stages of breast cancer

Data are emerging about the prognostic relevance of occult metastatic cells in the bone marrow of patients with various solid tumors. Discrepancies among different studies on the prognostic relevance of isolated tumor cells may be caused by tumor cell heterogeneity and the use of different immunoassays. There is increasing evidence that validated anticytokeratin antibodies (e.g., A45-B/B3) represent the present standard for the detection of isolated tumor cells. This immunocytochemical assay allows the identification of patients with occult tumor cell dissemination that cannot be identified by conventional screening methods in tumor staging. According to recent studies, these patients are at higher risk for subsequent development of distant metastases and might therefore benefit from early systemic therapy. At advanced stages of the disease, the micrometastatic tumor load after adjuvant therapy, or at the time of emerging recurrences, appears to reflect the tumor's ability to progress. Therapeutic monitoring and cell-cycle independent antibody-based therapy are among possible implications of this new, promising diagnostic tool. The present review also focuses on state of the art, reliable detection methods of occult metastatic cells in the bone marrow of breast cancer patients and on the prognostic relevance of these cells at different stages of the disease.

The 17-1A antigen is expressed on primary, metastatic and disseminated non-small cell lung carcinoma cells

In view of the high incidence of early distant tumor relapses in apparently completely resected (R0, M0) non-small cell lung cancer (NSCLC), there is a need for an adjuvant therapy. Considering the low tumor burden in these patients, an adjuvant therapy with monoclonal antibodies (i.e., the 17-1A MAb) might be appropriate. The purpose of our study was to test whether the 17-1A antigen is expressed on primary and metastatic NSCLC carcinoma cells. Using immunohistochemistry, the expression of 17-1A was analysed in primary tumors (n = 60) and in lymph node metastases (n = 7) of patients with NSCLC. Additionally, we investigated in 6 patients the expression of 17-1A on disseminated tumor cells in the bone marrow, which were detected by the pan-cytokeratin MAb A45-B/B3 using a double-labeling technique. The 17-1A antigen was homogeneously expressed in 47 (78.3%) out of 60 primary NSCLCs. The expression of 17-1A was independent from the tumor histology, the grade of differentiation, and other clinicopathological parameters (ploidy status, TNM-stage). Lymph node metastases were positive in 4 (57.4%) out of 7 cases. The double-labeling experiments demonstrated that 17-1A is coexpressed on disseminated tumor cells in the bone marrow in 5 (83%) out of 6 patients. The 17-1A antigen is expressed on the majority of primary, metastatic, and disseminated NSCLC cells. Patients with 17-1A-positive tumors might benefit from an adjuvant therapy with MAb 17-1A after completely resected NSCLC.

Comparative immunocytochemical assessment of isolated carcinoma cells in lymph nodes and bone marrow of patients with clinically localized prostate cancer

After radical prostatectomy for clinically localized prostate cancer, biochemical progression is seen in up to 40% of the patients due to persistent local and/or systemic remnants. Isolated disseminated carcinoma cells, undetectable by current staging methods, are of special interest as potential precursors of subsequent overt metastases. In the present study, immunohistochemistry (IHC) was performed to evaluate simultaneously the frequency of occult carcinoma cells in both lymph nodes (LNs) and bone marrow (BM) obtained from the iliac crests of 45 prostate cancer patients with untreated stage T(1-3) pN0 M0 prostatic carcinoma. IHC using monoclonal antibodies (MAbs) against epithelial cytokeratins was performed on 521 paraffin-embedded LNs histopathologically classified as tumorfree (pN0), as well as on BM cytospin preparations. To confirm the prostatic origin of positive cells in LNs, additional IHCs for prostate-specific antigen (PSA) and epithelial glycoproteins were performed. In total, isolated tumor cells in LNs and/or BM were detected in 17 of the 45 patients. Parameters such as tumor stage, grade and volume of the primary tumor as well as blood serum PSA levels could not detect patients harboring disseminated single tumor cells in LNs or BM. Following a median observation time of 24.9 months, no significant correlation between IHC positivity and PSA progression as a measure of early relapse was observed. Although the overall incidence of occult tumor cell spread corresponds to similar incidence of relapses after radical prostatectomy as reported by others, the fate of these cells needs to be evaluated in longer follow-up studies.

Suppression of metastasis formation by a recombinant single chain antibody-toxin targeted to full-length and oncogenic variant EGF receptors

Cytotoxic strategies which are directed to tumor-associated antigens might be most beneficial for cancer patients with minimal tumor load such as in an adjuvant setting after initial therapy. We have recently described a highly potent single chain antibody-toxin, scFv(14E1)-ETA, which consists of the variable domains of the antibody 14E1 genetically fused to a truncated form of Pseudomonas exotoxin A. ScFv(14E1)-ETA specifically recognizes the human epidermal growth factor receptor (EGFR) and the oncogenically activated receptor variant EGFRvIII, which have been implicated in the development of various human malignancies. Here we have investigated the antimetastatic activity of bacterially expressed scFv(14E1)-ETA and its disulfide-stabilized derivative ds-scFv(14E1)-ETA in a novel model for disseminated disease which is based on murine renal carcinoma cells subsequently transfected with the E. coli beta-galactosidase gene, and human full-length or variant EGFR cDNAs. Intravenous injection of these Renca-lacZ/EGFR and Renca-lacZ/EGFRvIII cells in syngenic Balb/c mice led to the formation of pulmonary metastases which were readily detectable upon excision of the lungs and X-gal staining. Systemic treatment of mice with scFv(14E1)-ETA resulted in the complete suppression of Renca-lacZ/EGFRvIII metastasis formation and drastically reduced the number of pulmonary Renca-lacZ/EGFR tumor nodules. The ds-scFv(14E1)-ETA derivative where the antibody variable regions are connected by an artificial disulfide bond displayed improved thermal stability at physiological temperature but due to reduced cytotoxic activity was less potent than the original scFv(14E1)-ETA in metastasis suppression.

Detection and characterization of carcinoma cells in the blood

A highly sensitive assay combining immunomagnetic enrichment with multiparameter flow cytometric and immunocytochemical analysis has been developed to detect, enumerate, and characterize carcinoma cells in the blood. The assay can detect one epithelial cell or less in 1 ml of blood. Peripheral blood (10-20 ml) from 30 patients with carcinoma of the breast, from 3 patients with prostate cancer, and from 13 controls was examined by flow cytometry for the presence of circulating epithelial cells defined as nucleic acid+, CD45(-), and cytokeratin+. Highly significant differences in the number of circulating epithelial cells were found between normal controls and patients with cancer including 17 with organ-confined disease. To determine whether the circulating epithelial cells in the cancer patients were neoplastic cells, cytospin preparations were made after immunomagnetic enrichment and were analyzed. Epithelial cells from patients with breast cancer generally stained with mAbs against cytokeratin and 3 of 5 for mucin-1. In contrast, no cells that stained for these antigens were observed in the blood from normal controls. The morphology of the stained cells was consistent with that of neoplastic cells. Of 8 patients with breast cancer followed for 1-10 months, there was a good correlation between changes in the level of tumor cells in the blood with both treatment with chemotherapy and clinical status. The present assay may be helpful in early detection, in monitoring disease, and in prognostication.