Abstract P2-01-12: Detection of circulating cancer stem cells: A novel approach as a predictive marker for breast cancer metastases. This may be especially useful in patients with undetectable circulating epithelial tumor cells

Background: Breast cancer is one of the most common types of cancer in women worldwide. It has been demonstrated that even localized tumors without clinically apparent metastases give rise to circulating epithelial tumor cells (CETCs). Recent studies have provided strong support for the circulating cancer stem cell (cCSC) hypothesis, which suggests that a more aggressive subpopulation of circulating tumor cells are the source of metastatic spread from the primary tumor. Measuring CETCs in blood of patients has emerged as a non-invasive diagnostic procedure for screening patients who may be at high risk for developing metastatic cancers. However, accurate detection of CETCs may provide erroneous results, since CETCs undergoing EMT during metastasis are down-regulated for the expression of epithelial cell markers.

Methods: 26 breast cancer patients were included into the study. The determination of CETCs and cCSC was performed using maintrac® method and tumorsphere forming assay, respectively. Cell viability, surface marker expression and ALDH 1 activity of the cells in the spheres were evaluated by fluorescence scanning microscope.

Results: Sphere formation was observed in 80 % of patients. We found that the number of tumorspheres depended on stage of disease. The number of tumorspheres increased significantly with tumor progression, especially with the presence of metastases. Tumorsphere formation was observed in all metastatic patients (median of 30 tumorspheres/100μl of blood), although only 27% of them had detectable CETCs. Analysis of surface marker expression profile showed that the cells in the spheres had typical phenotype of cancer stem cells. Sphere formation was not observed in healthy subjects (n=20).

Conclusion: There is a high correlation between the numbers of tumorspheres cultured from peripheral blood with clinical stage of disease. This may be an indicator of tumor aggressiveness, especially presence of metastases and may provide clinically useful prognostic information.

Citation Format: Pizon M, Schott D, Pachmann U, Pachmann K. Detection of circulating cancer stem cells: A novel approach as a predictive marker for breast cancer metastases. This may be especially useful in patients with undetectable circulating epithelial tumor cells [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-01-12.

Abstract P3-01-17: PD-L1 expression on circulating epithelial tumor cells (CETCs) correlates with aggressiveness of tumor in breast cancer patients

Background: Strategies to improve the efficacy of the immune system against malignant tumors represent a major innovation focusing on the programmed death-1 receptor (PD-1), with its two ligands PD-L1 and PD-L2. The expression of PD-L1 has been evaluated in a number of different tumor types and can be used as a predictive biomarker for PD-1/PD-L1 checkpoint inhibitor treatment response. We used a non-invasive, real-time liquid biopsy to better characterize PD-L1 expression on circulating epithelial tumor cells (CETCs) in breast cancer patients.

Methods: CETCs were determined from blood of 72 patients suffering from breast cancer. The number of vital CETCs and their expression of PD-L1 was investigated using the maintrac® method.

Results: PD-L1 expressing CETCs were detected in 94.5 % of breast cancer patients. Breast cancer patients with metastatic disease had significantly more PD-L1 positive CETCs as compared to patients without metastasis (median 75% vs. 61.1%; p<0.05). Furthermore, patients with positive lymph node status had significantly more PD-L1 positive CETCs as compared to patients with negative lymph nodes (median 60% vs. 93%, p<0,05). Moreover, we observed a significant heterogeneity in PD-L1 immunostaining intensity across CETCs from the same patients.

Conclusion: Breast cancer patients have detectable CETCs with a high frequency of PD-L1 which correlates with progression of cancer disease. PD-L1 seems to be a major factor in immune evasion and may be a promising target of anticancer therapies. Monitoring the frequency of PD-L1 positive CETCs could reflect individual patient's response to an anti-PD-1/PD-L1 therapy.

Citation Format: Schott D, Pizon M, Pachmann U, Pachmann K. PD-L1 expression on circulating epithelial tumor cells (CETCs) correlates with aggressiveness of tumor in breast cancer patients [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-01-17.

Circulating epithelial cells in patients with thyroid carcinoma

Goal: To investigate whether circulating epithelial cells (CEC) recognized via the epithelial cell adhesion molecule (EpCAM) can be identified in the blood of patients with thyroid carcinoma, given that CEC have already been detected in other types of carcinoma and are considered a potential marker of tumour dissemination. Patients, methods: Blood samples of patients with active differentiated thyroid carcinoma (DTC) (n = 50) were compared to samples of patients with: a) recent surgical excision of a thyroid carcinoma (postOP-DTC) (n = 16); b) athyreotic, tumour-free status after radioiodine ablation (AT-DTC) (n= 33); and c) benign thyroid diseases (BTD) (n = 51). Samples of volunteers with normal thyroid parameters (NT) (n = 12) were also investigated. Cells from EDTAblood were subjected to erythrocyte lysis, isolated by centrifugation, and incubated with a fluorescence-labeled antibody against EpCAM. The numbers of vital cells were counted via fluorescence microscopy. Results: CEC were identified in all groups, with the postOP-DTC group showing the highest mean CEC numbers of all groups. The DTC group had significantly higher CEC numbers than the NT group, and numerically higher numbers than the other groups, although not reaching statistical significance. Within the DTC group there was a correlation between levels of serum thyroglobulin and numbers of CEC (r = 0.409, p = 0.003). Conclusions: High CEC numbers were not specific to thyroid carcinoma. The methodology used here, based on a single measurement does not allow to identify severe forms of DTC, emphasizing the need of longitudinal measurements throughout therapy. Detection and characterization of tumour thyroid cells in circulation should be based on additiona l consideration of tissue-specific characteristics.

Abstract P3-07-59: Stem cell markers are overexpressed in tumorspheres cultured from circulating epithelial tumor cells (CETCs) in patients with breast cancer

Background:

Breast malignancies continuously shed tumor cells which may enter the circulation, spread to other tissue and initiate metastases, but only a small subpopulation among CETCs is capable of metastasis formation. The subpopulation of CETC capable of forming tumorspheres in vitro and carrying stem cells properties is assumed to have metastatic potential. The aim of this study was to characterize the pattern of expression of the tumorspheres as compared to CETCs.

Methods:

Blood samples were obtained from patients diagnosed with breast tumors. CETCs were enumerated with maintrac method and subsequently cultivated in stem cell-selective medium. The expression of stem cell marker genes EpCAM, Nanog, Okt4 Sox2, ALDH and CD133 were detected by RT-PCR in single CETCs and tumorspheres.

Results:

0.1- 10% of CETCs could form non-adherent tumorspheres under stem cell- selective conditions after a period of 14 days. Array qRT-PCR analysis revealed that putative stem cell markers, such as Oct4, Sox2, Nanog, EpCAM, ALDH1 and CD133 are overexpressed in relation to house-keeping genes RPL13a and GAPDH in tumor spheres in contrast to the significantly lower expression level of these stem cell markers in individually isolated CETCs. High expression level of pluripotency genes in tumorspheres was associated with aggressive tumor behaviour in terms of tumor progression and type of cancer.

Conclusion:

Thus, differential expression of stem cell markers in CETCs and tumorspheres substantiates the hypothesis that only a small population of circulating tumor cells possess the stem cell properties and are responsible for metastasis formation.

Citation Format: Zimon D, Pizon M, Mayer V, Pachmann K. Stem cell markers are overexpressed in tumorspheres cultured from circulating epithelial tumor cells (CETCs) in patients with breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-59.

[Circulating tumor cells in head and neck cancer]

Circulating tumor cells are defined as tumor cells which are circulating in the peripheral blood of the cancer patient. While several large studies have investigated the role of circulating tumor cells in other solid tumors, the importance of these tumor cells in patients with head and neck cancer was turned into the focus not until the recent years. In other solid tumor the presence of circulating tumor cells often seems to be a negative prognostic marker and seems to be a marker for therapy response. The present article wants to give an overview about the knowledge on circulating tumor cells and their clinical relevance in head and neck cancer. The methodology to detect circulating tumor cells will be critically reflected. The future potential of the detection of circulating tumor cells in head and neck cancer patients will be discussed.

The influence of radioiodine therapy on the number of circulating epithelial cells (CEC) in patients with differentiated thyroid carcinoma - a pilot study

GOAL

The aim of this pilot study was to investigate the changes of circulating epithelial cells in the blood of patients with differentiated thyroid cancer after radioiodine-therapy with I-131.

METHODS

The cells were detected by fluorescence-microscopy via the epithelial-cell-adhesion-molecule (EpCAM), a molecule described to be over-expressed in most carcinoma tissues and also present on circulating cells deriving from primary site. Epithelial cells were assessed before radioiodine-therapy, as well as 2 days, 14 days, and 3 months after therapy. 2 patient groups were examined: 1) patients with thyroid cancer receiving a first radioiodine-therapy after thyroidectomy (RITfirst, n=13), and 2) patients with thyroid cancer in need of repeated radioiodine-therapy due to local or metastatic recurrences (RITrep, n=15). Circulating epithelial cell changes were correlated to changes of serum-thyroglobulin and to clinical response evaluated 3 months after therapy.

RESULTS

Patients with an early decrease of cells after radioiodine-therapy (RITfirst 7/13; RITrep 2/15) showed an increase of serum-thyroglobulin in most of the cases (RITfirst 5/7; RITrep 2/2). In the RITrep group, a decrease in cell counts 2 days after radioiodine-therapy indicated a clinical response in 90% of the cases.

CONCLUSIONS

This study indicates that the number of circulating epithelial cells in differentiated thyroid cancer undergo changes in response to radioiodine-therapy. The destruction of cells through radioiodine-therapy may induce a short-term release of thyroglobulin in the blood. A clear relationship between the clinical outcome and the cell changes could not be found, but early cell decreases may help identifying patients more likely to respond to radioiodine-therapy.

Abstract PD6-1: Tumor spheres growing from peripherally circulating tumor cells exhibit stem cell features

Background: Among the cells that are disseminated from a malignant tumor only very few are capable to resettle in distant organs and grow into life-threatening metastases. Therefore, the question arises how and whether such cells which have the potential to grow into metastases can be detected. It has been shown that a subpopulation of cells from breast cancer tissue can form so-called mammospheres with stem cell features. Here we show that such tumor spheres can also be grown from peripherally circulating tumor cells from breast cancer patients in different stages of disease

Materials and Methods: Using a nondissipative approach with only one enrichment step of red blood cell lysis, the cells from the pellet, containing the white blood cells together with the putative tumor cells were cultured under conditions favoring the growth of epithelial cells. At 7, 14 and 21days the cell cultures were inspected for the appearance of spheroids staining with anti-EpCAM, anti-CD24 and anti-CD44 antibody and.expressing ALDH1.

Results: Peripherally circulating cells from patients with malignant tumors in different stages of disease were analyzed for the presence of circulating epithelial tumor suspect cells and the frequencies of tumorspheres. Tumorspheres could so far be grown from 79% of 36 patients in whom more than 1700/ml epithelial tumor suspect cells were detected. Numbers of tumorspheres varied from 1 to 29 /ml and correlated with the aggressiveness of the tumor. Surprsingly the numbers were highest in patients after surgery who had not yet received any systemic therapy. The size of the spheres increased from day 7 to day 21. The spheres were negative for CD24 and positive for CD44. They highly express ALDH1 and thus exhibite typical features of stem cells.

Conclusion: Here, we demonstrate that the circulating tumor cells, detected in our approach contain a subpopulation with stem cell-like properties capable of growing into tumorspheres. The frequency and growth potential of cells capable of forming spheres seems to be dependent from the properties of the primary tumor. The possibility to grow tumorspheres from peripherally circulating tumor cells may open up a new field, where the relevant cells with stem cell properties from individual patients can now be specifically analysed further for genetic endowment, transcriptional activity, heterogeneity and stem cell markers.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD6-1.

Heterogeneity of circulating epithelial tumour cells from individual patients with respect to expression profiles and clonal growth (sphere formation) in breast cancer

Background

The detection of tumour cells circulating in the peripheral blood of patients with breast cancer is a sign that cells have been able to leave the primary tumour and survive in the circulation. However, in order to form metastases, they require additional properties such as the ability to adhere, self-renew, and grow. Here we present data that a variable fraction among the circulating tumour cells detected by the Maintrac^® approach expresses mRNA of the stem cell gene NANOG and of the adhesion molecule vimentin and is capable of forming tumour spheres, a property ascribed to tumour-initiating cells (TICs).

Patients and methods

Between ten and 50 circulating epithelial antigen-positive cells detected by the Maintrac approach were selected randomly from each of 20 patients with breast cancer before and after surgery and were isolated using automated capillary aspiration and deposited individually onto slides for expression profiling. In addition, the circulating tumour cells were cultured without isolation among the white blood cells from 39 patients with breast cancer in different stages of disease using culture methods favouring growth of epithelial cells.

Results

Although no epithelial cell adhesion molecule (EpCAM)-positive cells expressing stem cell genes or the adhesion molecule vimentin was detected before surgery, 10%–20% of the cells were found to be positive for mRNA of these genes after surgery.

Tumour spheres from circulating cells of 39 patients with different stages of breast cancer were grown without previous isolation in a fraction increasing with the aggressivity of the tumour.

Summary

Here we show that among the peripherally circulating tumour cells, a variable fraction is able to express stem cell and adhesion properties and can be grown into tumour spheres, a property ascribed to cells capable of initiating tumours and metastases.

Abstract P1-07-16: Liver derived epithelial cells as source of false positive circulating tumor cells in early breast cancer

The MAINTRAC technique as introduced by our coworkers from Jena (RBC lysis, fluorometric detection and analysis on Olympius ScanR) detects more circulating epithelial cells than techniques using enrichment. Also cells with a low EPCAM expression are detected and not only the typical cells with bright expression found after immunomagnetic enrichment. The relative cheapness and reproducibility allows frequent monitoring during and after therapy Using 3 colour detection (EPCAMfitc, DAPI, Vimentin PE) living and dead circulating epithelial cells in EMT, or cells in EMT with stemcell markers (EPCAMfitc, Vimentin-PE, CD44PacBlue) can be detected. In early breast cancer (n = 135) cells can be found in 60% of patients and in 40% higher cell counts (>100 ml are detectable. A control population(n = 100) showed low numbers in 98% (e.g (<100 CECin 1 ml blood). Expression of the mesenchymal marker (vimentin) ranges between 10 and 40% with different expression. CD44 shows also a wide range of expression. Two main cell types can be distinguished: type 1 shows generalized but weaker expression patterns and a second type with very bright dotted expression. The clinical relevance of these subsets is not known and their behavior under therapy has not been analysed in depth yet. In advanced breast cancers high cell counts were detectable in most patients with a less agressive disease course. In the rapidly progressing unfavorable subtypes (TN and Her2+. HRneg) less or none cells were found. During crossvalidation in non cancer patients we found high cell numbers in several forms of liver affections (n = 108). The expression patterns of markers on these cells were not differing from those in cancer patients. So this same cell type merging EMT, stemcell an hypoxic stress markers is detectable in advanced and early breast cancer (n = 40) and in benign disease. These cells disappear or decrease after response to chemo or anti-hormonal therapy in cancer or antioxidant therapy in NAFLD. We believe that the evasion of these cells is driven by the same force in cancer as in non cancer conditions. We suggest that this are the wellknown hypoxic and hyperacidic conditions causing epithelial mesenchymal transition. Cancer cell hijack this functions occurring normally under these conditions to survive and to facilitate evasion. More comprehensive analysis (four colour analysis on the AMNIS Flowsight) is needed and should show differences in expression patterns of liver derived epithelial cells (LDEC) and real tumor derived epithelial cells (TDEC). Further clarification of these phenomena should give new insights of the biological events in early disease and the possibilities and reliability of “fluid biopsy”.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-07-16.

Abstract P5-03-13: Detection of tumor initiating cells (TIC) among the peripherally circulating epithelial tumor cells from patients with breast cancer

Background: The detection of tumor cells circulating in the peripheral blood of patients with breast cancer is a sign that cells have been able to leave the primary tumor and survive in the circulation. However, in order to form metastases they require additional properties such as the ability to adhere, self renew and grow. Here we present data that a variable fraction among the circulating tumor cells detected by the maintrac® approach express mRNA of the stem cell gene nanog and of the adhesion molecule vimentin and are capable of forming tumor spheres a property ascribed to TIC.

Patients and methods: Between 10 to 50 circulating epithelial antigen positive cells detected by the maintrac® approach were selected randomly from each of 20 patients with breast cancer before and after surgery and isolated using automated capillary aspiration and deposited individually onto slides for expression profiling. In addition, the circulating tumor cells were cultured without isolation among the white blood cells from 5 patients with breast cancer in different stages of disease using culture methods favoring growth of epithelial cells.

Results: Although no EpCAM mRNA positive cells expressing stem cell genes or the adhesion molecule vimentin were detected before surgery, 10 to 20% of the cells were found to be positive for mRNA of these genes after surgery. Most surprisingly, it was possible to grow tumor spheres (Fig 1) from these circulating cells without previous isolation in all patients in a fraction comprising between 1% of the epithelial antigen positive cells in patients with newly diagnosed tumor up to 10% in a patient with advanced breast cancer.

Conclusion: We here show, that among the peripherally circulating tumor cells a variable fraction is able to express stem cell and adhesion properties and can be grown into tumor spheres, a property ascribed to cells capable of initiating tumors and metastases.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-03-13.

Circulating Epithelial Tumor Cell (CETC) Monitoring during SERM and Aromatase Inhibitor Treatment for Early Detection of Patients Resistant to Tamoxifen

The observation, that part of breast cancer patients benefit from ovarectomy led to the realization that in these patients the estrogen receptor crucially contributes to the growth potential of malignant tumors of the female reproductive system. This has led to the development of compounds specifically binding to the estrogen receptor but without activating activity. Although this has led to an impressive improvement in relapse free survival a considerable part of patients some of which being carriers of the CYP2D6 polymorphism will not respond to this targeted treatment. Therefore, in addition to defining the subpopulation with a high probability of responding to the targeted therapy only an immediate control of the response to treatment will ultimately improve outcome.Epithelial tumor cells circulating in peripheral blood are easily accessible and have been shown to reflect the response of the tumor to therapy. They can, therefore, be used to monitor the effect of therapy also in the adjuvant situation when the tumor has been removed by surgery.Here we report on the application of therapy monitoring using CETCs during adjuvant hormone blocking therapy. ER positive breast cancer were prospectively analysed for the number of CETC before therapy, before each new cycle of chemotherapy and during maintenance therapy with tamoxifen of aromatase inhibitor or during switch from one principle to the other. 1ml of blood was drawn into EDTA vials, red blood cells lysed and the white blood cell pellet stained with FITC-labelled anti-Epcam. Green fluorescent cells were detected by image analysis and dead cells excluded due to red PI fluorescence.178 patients were followed initially at quarterly intervals and later at annual intervals for their numbers of CETCs. 131 patients remained disease free during the observation interval of up to 7 years and 47 (26%) suffered distant relapse. Of the patients in complete continuous remission, 58% showed decreasing or stable CETCs whereas in the patients with relapses 73% showed increasing CETCs.45 patients were subsequently switched to aromatase inhibitor treatment, 17 relapsed patients and 28 patients without evidence of disease. Of the relapsed patients 35% have remained progress free all with a re-decrease in CETCs during AI treatment.Thus, gauging of CETCs can help to monitor hormone treatment and in the future contribute to early switch patients to AI if an increase in CETCs indicates resistance to tamoxifen.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5129.

Chemosensitivity Testing of Circulating Epithelial Cells (CETC) in Breast Cancer Patients and Correlation to Clinical Outcome

In spite of ample prognostic markers available in breast cancer, still a considerable proportion of patients with good prognostic markers suffers relapse whereas patients with poor prognostic markers may remain disease free. It would, therefore, be desirable to control, at the individual patient level, whether the applied therapy is effective. Our previous work indicates, that in cancer patients most of the epithelial cells circulating in peripheral blood (CETC) are part of the tumor and that the response of these cells reflects the response of the tumor to the applied therapies.Therefore, these cells were used to assay chemosensitivity in short time cultures analyzing the percent of cell killing during short time incubation and monitoring the decrease or increase in numbers of these cells during treatment with the respective agents providing a unique tool for therapy surveillance. Patients were prospectively analysed for the number of CETC before each new combination of chemotherapy. 1ml of blood was drawn into EDTA vials, red blood cells lysed and the white blood cell pellet stained with FITC-labelled anti-Epcam. Green fluorescent cells were detected by image analysis and dead cells excluded due to red PI fluorescence. Activity of individual compounds was determined using three different concentrations of each compound at 3h, 6h and 12hs and displayed as % cell killing. The in vitro results were then compared to in vivo reduction of CETCs and to the reduction of a marker lesion.215 patients have been investigated so far. Cell killing was dose and time dependent. The highest killing rates were observed with Epirubicin and Taxanes, agents which are known for their high activity in breast cancer. Less than 20% killing activity was termed marginal activity. In vitro sensitivitity was highly significantly predictive of in vivo CETC reduction. In some cases an increasing resistance could be shown to develop during repeated cycles of the same combination therapy. CETC reduction was correlated with a prolonged progression free survival.Thus this approach can in the future be used to test in advance the sensitivity of the circulating tumor cells to chemotherapy and at the same time monitor the current response of the cells to therapy in vivo in order to optimize and individualize therapy.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2044.

Changing Therapy as a Consequence of the Behaviour of CETC during Adjuvant Trastuzumab Treatment in Patients with Her2/Neu Positive Breast Cancer

Gene silencing, demethylation, translocations and amplifications crucially contribute to the growth potential and aggressiveness of malignant tumors. This has led to the development of compounds specifically targeting such alterations. Although parts of these compounds have led to an impressive improvement in relapse free survival such as trastuzumab in breast cancer treatment, a considerable part of patients carrying the alteration will not respond to this targeted treatment. Therefore, in addition to defining the subpopulation of patients with a high probability of responding to the targeted therapy only immediate control of the response to treatment will ultimately improve outcome.Epithelial tumor cells circulating in peripheral blood are easily accessible and have been shown to reflect the response of the tumor to therapy. They can, therefore, be used to monitor the effect of therapy.Here we report on the application of therapy monitoring using CETCs during adjuvant trastuzumab treatment and the consequences which may be deduced from these observations for individualized therapy.30 patients with either IHC3+ or FISH confirmed Her2/neu positive breast cancer were prospectively analysed for the number of CETC before therapy, before each new cycle of chemotherapy and during maintenance therapy with trastuzumab.1ml of blood was drawn into EDTA vials, red blood cells lysed and the white blood cell pellet stained with FITC-labelled anti-Epcam. Green fluorescent cells were detected by image analysis and dead cells excluded due to red PI fluorescence.Most patients showed the typical response of high risk patients upon chemotherapy with an initial decrease in cell numbers followed by a rapid reincrease still during chemotherapy. The subsequent maintenance therapy with trastuzumab led to a stabilization or a decrease in CETC numbers in 89% of patients all of which are in sustained complete remission whereas all of the 11% patients with increasing CETCs have suffered relapse. Thus CETC monitoring allowed an excellent discrimination of patients at risk of relapse also during trastuzumab treatment.To further investigate the reason for treatment failure in the patients with increasing CETCs the cells were additionally analysed for their status of Her2/neu amplification during treatment. At the end of chemotherapy cells with a low number of Her2/neu amplificates comprised between 80 and 100% whereas cells with more than 10 signals comprised between 0 and 20%. During the subsequent therapy with trastuzumab the fraction of cells with more than 10 signals continuously increased to between 50 and 60%. This indicates that in these patients trastuzumab was not capable of eliminating the cells with a high Her2/neu amplification probably because the concentration of trastuzumab is not sufficient to eliminate these cells. With regard to the high probability with which a relapse must be expected in these patients a trial using higher trastuzumab doses seems warranted in patients with increasing CETC during the conventional trastuzumab treatment. Alternatively lapatinib might be an option.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2088.

Circulating Epithelial Cells as a Tool for Monitoring Treatment Success of Primary Chemotherapy with Simultaneous or Sequential and without Trastuzumab

In spite of ample prognostic markers available in breast cancer, still a considerable proportion of patients with good prognostic markers suffers relapse whereas patients with poor prognostic markers may remain disease free. It would, therefore, be desirable to control, at the individual patient level, whether the applied therapy is effective. Our previous work indicates, that in cancer patients most of the epithelial cells circulating in peripheral blood (CETC) are part of the tumor and that the response of these cells reflects the response of the tumor to the applied therapies.Therefore monitoring the decrease or increase in numbers of these cells providing a unique tool for therapy surveillance was used to monitor neoadjuvant chemotherapy in 26 her2/neu positive breast cancer patients with either IHC3+ or FISH confirmed Her2/neu positive breast cancer. Patients were prospectively analysed for the number of CETC before therapy, before each new cycle of chemotherapy and during maintenance therapy at each visit initially every three months and subsequently at more extended intervals. 1ml of blood was drawn into EDTA vials, red blood cells lysed and the white blood cell pellet stained with FITC-labelled anti-Epcam. Green fluorescent cells were detected by image analysis and dead cells excluded due to red PI fluorescence.After an initial variable reduction of CETC during neoadjuvant chemotherapy, tightly connected to tumor reduction we regularly observed a massive release of cells from the shrinking tumor. Although these cells may not be able to settle in tumors with low metastatic potential, in 4/4 patients with Her2/neu positive tumors who did not receive trastuzumab the number of CETCs further increased after termination of therapy and surgery followed by rapid distant relapse indicating that the cells released in these patients may be highly aggressive with a high potential to settle and grow into metastases.It is, however not clear, whether sequential or simultaneous addition of trastuzumab to chemotherapy is preferential. In our hands 65% of the patients receiving simultaneous trastuzumab showed increasing CETCs and all have suffered relapse whereas all patients with decreasing CETCs are still in complete remission indicating that in the neoadjuvant situation during maintenance therapy an increase in CETC is the earliest indicator of imminent relapse.6/6 patients who received trastuzumab sequentially to the neoadjuvant treatment all showed decreasing numbers with all of them still without signs of disease after 4 years of follow up. Thus, trastuzumab was highly effective in this treatment and even if the tumor cells were not eliminated immediately, trastuzumab contributed to prevent them from settling and growing into metastases and CETC monitoring favours sequential trastuzumab.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3016.

The Carboxymethyl Dextran Shell is an Important Modulator of Magnetic Nanoparticle Uptake in Human Cells

In oncology and hematology the separation of tumor cells from healthy cells in peripheral blood is a vital problem. We could show previously, that enrichment of tumor cells from peripheral blood is possible by using magnetic nanoparticles with a carboxymethyl dextran (CMD) shell. Long-term storage of CMD nanoparticles eliminated the differential labeling of tumor cells and leukocytes which might be due to an alteration of the carboxymethyl dextran shell. Incubation of stored CMD nanoparticles with freshly prepared carboxymethyl dextran restored the differential labeling. In contrast, enzymatic degradation of the carboxymethyl dextran shell with dextranase abolished the cell-type specific labeling. Thus, an intact carboxymethyl dextran shell is crucial for the cell-type specific interaction of the CMD nanoparticles and living cells.

Gauging the response of circulating epithelial tumor cells (CETC) and tumor stem cell subpopulations to therapy of early-stage cancer in the individual patient

11026

Background: Cells released from the primary tumor persisting and recirculating in the host can lead to the formation of distant metastases. It was claimed that such cells are detectable only in a minor fraction of early-stage cancer patients but we can show that CETC are detectable and can be quantified in the peripheral blood of almost all cancer patients including early-stage solid malignancies. Methods: Using anticoagulated peripheral blood, red blood cell lysis as the only enrichment step, one centrifugation step, staining live cells with fluorochrome labelled anti-epithelial antigen as a search antibody, automated image analysis for detection of positive events and evaluation of exclusively surface located epithelial antigen on vital unfixed cells, CETC were detected in most patients with early stage cancer. Subsequently cells could be stained with anti-ALDH-antibody and in situ hybridized for HER2/neu amplification and quantified repeatedly during neo/adjuvant chemotherapy and during maintenance therapy with hormones or trastuzumab. Results: We here report the results from 497 breast cancer patients analyzed more than three times during the course of disease, 248 during neoadjuvant/adjuvant chemotherapy, 249 during trastuzumab and or hormone therapy. Different pattern of therapy response were obtained with rapidly responding CETC changes over several logs in response to chemotherapy and slow and long-lasting changes extending over several years in response to hormone therapy and trastuzumab. Stem cell like staining was seen in a minor fraction of cells (1%) in about 10% of patients. An increase in cell numbers and in the fraction of HER2/neu amplified cells was under all treatment conditions unequivocally significantly correlated to highly increased risk of relapse. Conclusions: CETC and subpopulation monitoring provides an invaluable tool for prompt gauging of systemic therapy in early stage solid tumors as a tool for therapy guidance and optimal personalized therapies to improve therapy results and spare unnecessary treatments.

No significant financial relationships to disclose.

Behaviour and metastatic potential of her2/neu positive and her2/neu negative circulating epithelial tumor cells (CETC) during adjuvant systemic therapy in breast cancer

Abstract #5030

Background: Most tumor patients do not die from the primary tumor but from metastases in vital organs. Here we report on the influence of adjuvant chemotherapy and trastuzumab on the remnant CETC patients with her2/ positive tumors after surgery and the impact on metastasis formation.
 Material and Methods: Tumor cells were quantified with an automated microscope (Laser Scanning Cytometer®, Icis or ScanR) from anticoagulated blood drawn before each new therapy cycle from patients treated with systemic chemotherapy after surgery and subsequent maintenance therapy with trastuzumab. After red blood cell lysis leucocytes were stained with PE-anti-CD45 and tumor cells with FITC-anti-EpCAM. FISH analysis was performed for determination of the proportion of her2/neu positive cells and changes registered as % increase or decrease. The response to therapy was correlated to outcome.
 Results: Almost all her2/neu positive breast cancer patients scheduled for systemic treatment had CETC before therapy. A decrease in cell numbers highly correlated with relapse free survival. Her2/neu positive patients responding to therapy with an increase in CETC were at increased risk to develop further increasing cell numbers also during subsequent trastuzumab treatment. Her2/neu positive patients who did never receive trastuzumab all had increasing CETC numbers during the postoperative observation time and all have suffered relapse. Patients who received trastuzumab only after adjuvant treatment all had decreasing CETC numbers and all are in sustained complete remission after up to 4 years. Of the patients who received trastuzumab together with adjuvant treatment those who showed no change or an increase in CETC in spite of trastuzumab had increasing proportions of FISH high amplified cells and a higher risk of relapse than patients with decreasing CETC during trastuzumab.
 Discussion: Monitoring CETC will not only provide the earliest and most reliable indicator of successful adjuvant treatment and spare patients unnecessary treatment but also patients with the highly aggressive her2/neu positive tumors can be discerned into such with high and low risk of relapse even during trastuzumab therapy. This warrants further therapy studies to control what patients may benefit from addition of e.g. small molecules already during therapy before development of metastases.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5030.

Detection of tumor stem cells among circulating epithelial tumor cells (CETC) and relationship to therapy response

Abstract #5053

Background: It has been shown that the metastatic process is highly inefficient. Thus in the experimental setting, using breast cancer cell lines, only 0,1 to 0.01% of the injected cells are capable of forming metastases. With respect to cells released form primary tumors it is neither known, how many cells survive in the circulation nor what proportion is capable of forming metastases. Therefore we have attempted to determine the fraction of stem cells among the CETC and to correlate their frequency to relapse.
 Material and Methods: Tumor cells were quantified with an automated microscope (Laser Scanning Cytometer®, Icis or ScanR) from anticoagulated blood drawn before each new therapy cycle from patients treated with systemic chemotherapy after surgery and subsequent maintenance therapy. After red blood cell lysis leucocytes were stained with PE-anti-CD45 and tumor cells with FITC-anti-EpCAM. Tumor stem cells were tried to define in 2 ways: 1. Using PE-conjugated anti-CD24 Epithelial antigen positive cells were counterstained and the CD24 negative cells determined. 2. Using the Aldefluor method epithelial cells staining intracellularly positive were determined and changes registered as % increase or decrease. The response to therapy was correlated to outcome.
 Results: Both methods were well applicable. With the anti-CD24 counter stain, most CETC stained positively. A minor fraction of less than 1% of CETC was lacking CD24 staining and was regarded as the CD24 negative stem cell population. With regard to the Aldefluor method, both green fluorescing FITC anti-CD326 and red fluorescing Dye-anti-CD326 were used for screening of CETC and subsequently green intracellular fluorescence was determined inside the CETC. Aldefluor positive CETC also were in the range of 1%. Patients with CETC increasing during systemic chemotherapy which are defined as poor prognosis patients are now investigated for their proportion of stem cells during CETC increase.
 Discussion: These analyses will help to clarify whether an increase in CETC during systemic chemotherapy is due to tumor stem cells, surviving conventional chemotherapeutic agents and whether they might be susceptible to new agents.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5053.

The relevance of circulating epithelial tumor cells (CETC) for therapy monitoring during neoadjuvant (primary systemic) chemotherapy in breast cancer

BACKGROUND

Having demonstrated in a previous report that the response of circulating epithelial tumor cells (CETC) during the first cycles of primary (neoadjuvant) chemotherapy perfectly reflects the response of the tumor, in the present study the changes in cell numbers during subsequent cycles and their possible impact on the therapy's outcome were examined.

PATIENTS AND METHODS

In 58 breast cancer patients CETC were quantified during therapy with either EC (epirubicin/ cyclophosphamid) or dose intensified E (epirubicin) followed by taxane, with or without trastuzumab, and subsequent CMF (cyclophosphamid/methorexate/ fluorouracil).

RESULTS

CETC numbers declined more than 10-fold (good response) in 65% (her2/neu-negative) and 55% (her2/neu-positive) of patients during EC, and in 60% during dose intensified E, respectively, followed by an increase of CETC in all patients. CETC remained increased, decreasing only when adding CMF. A good initial response correlated with estrogen-receptor negativity, a poor response with early distant relapse (P < 0,0001, hazard ratio = 11.91).

CONCLUSION

Response of CETC already during the first cycles of neoadjuvant treatment predicts the final response of the tumor. Hitherto unknown effects of the release of tumor cells during therapy further our understanding of tumor-blood interaction and may improve access of agents like antibodies to cells. The impact on the further course of disease remains to be evaluated.

Monitoring of circulating tumor cells during systemic therapy allows distinguishing breast cancer patients at risk for relapse

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Background: Recent refinement of methods, allowing detection of minimal numbers of residual cells from malignant tumors have reactivated the debate, to what extent single tumor cells in lymph nodes, bone marrow and peripheral blood can be considered as “micrometastases”. The presence of such cells, indeed, reflects only the first step in the metastatic process, dissemination, and the formation of metastases from such cells seems to be quite ineffective. If, however these cells react to therapy in an identical way as the tumor itself, these cells can be used to monitor therapy response very early during primary systemic (neoadjuvant) therapy, during adjuvant therapy, where no other target is available to control therapy success and already during therapy initiation in metastatic disease. Methods: Circulating epithelial cells were enumerated from 1 ml of anticoagulated blood after red blood cell lysis, staining of live cells with a fluorochrome labeled anti-epithelial antibody and automated microscopy before and after each chemotherapy cycle for monitoring of therapy success. Results: The response of the peripherally circulating cells of 35 patients with breast cancer treated with neoadjuvant chemotherapy varied from marginal (less than tenfold) to highly responsive (more than thousand fold) already during the first three to four courses and showed identical response to therapy as the whole tumor with a correlation of p > 0.9. The method was subsequently applied to monitor the response of such cells in the adjuvant treatment. In the first 25 patients with a follow up of more than 4 years, an increase in cell numbers already from the begin of therapy or following an initial response was observed in 20% of patients and all of these patients have subsequently relapsed (p<0,0001). These results have now been corroborated in a total of 148 patients, confirming a hazard ratio of 25 for relapse in the following 5 years for patients with increasing cell numbers during therapy independent of therapy regimen and a significance of p<0.0001. Conclusions: Quantitative monitoring of circulating tumor cells can be used as a tool for therapy survey in breast cancer in the absence of manifest tumor.

No significant financial relationships to disclose.

Treatment with granulocyte-colony stimulating factor in patients with acute myocardial infarction. Evidence for a stimulation of neovascularization and improvement of myocardial perfusion

BACKGROUND

Stem cell therapy has been suggested to be beneficial in patients after acute myocardial infarction (AMI). Strategies of treatment are either a local application of mononuclear bone marrow cells (BMCs) into the infarct-related artery or a systemic therapy with the granulocyte-stimulating factor (G-CSF) to mobilize BMCs. Nevertheless, the mechanisms responsible for improvement of cardiac function and perfusion are speculative at present. This study has been performed to investigate the effect of G-CSF on systemic levels of vascular growth factors and chemokines responsible for neovascularization, that might help to understand the positive effects of a G-CSF therapy after AMI.

METHODS AND RESULTS

Five patients in the treatment group and 5 patients in the control group were enrolled in this study. The patients in the treatment group received 10 microg/kg bodyweight/day of G-CSF subcutaneously for a mean treatment duration of 6.6 +/- 1.1 days. In both groups, levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and monocyte chemotactic protein-1 (MCP-1) were measured on day 2 to 3 and day 5 after AMI. The regional wall perfusion and the ejection fraction (EF) were evaluated before discharge and after 3 months with ECG-gated MIBI-SPECT and radionuclide ventriculography, respectively. Significant higher levels of VEGF (p < 0.01), bFGF (p < 0.05) and MCP-1 (p < 0.05) were found in the treatment group compared to the control group. Levels of VEGF and bFGF remained on a plateau during the G-CSF treatment and decreased significantly in the control group. The wall perfusion improved significantly within the treatment group and between the groups (p < 0.05), respectively. The EF improved significantly within the treatment group (p < 0.05), but the change of the EF between the groups was not significant.

CONCLUSION

In patients with AMI, the treatment with G-CSF modulates the formation of vascular growth factors that might improve neovascularization and result in an improved myocardial perfusion and function.

Circulating tumor cells: Tools for monitoring and targets for therapy

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Background: Analysis of peripheral blood may help to early monitor the process of dissemination of metastatic cells into vital organs . The true number of circulating epithelial tumor cells (CETC) being still controversial, we, omitting all possibly selective enrichment procedures, detect a considerable number of such cells in breast cancer patients. CETC have been shown to respond to therapy in exactly the same way as the primary tumor and we have now probed CETC for monitoring effectiveness of adjuvant therapy. Methods: CETC were monitored in 97 patients before and after each cycle during adjuvant therapy using fluorchrome labeled antibody against epithelial antigen and laser scanning fluorimetry. Results: CETC could be detected in all patients after surgery. Four different forms of therapy response were observed: Patients with 1) CETC from ER+PR+ tumors responding only marginally with appreciable numbers remaining after therapy. These patients (about 40% of patients) have remained in CR; 2) rapidly decreasing CETC,sometimes to below the threshold of detection. These patients, too, remained in CR; 3) constantly or intermittently increasing resistant cells. All these patients have experienced early relapse 5–24 months after diagnosis); 4) Most interestingly, some cells initially respond very well to therapy but show a renewed increase during continuing therapy. These patients, too, have relapsed. Conclusion: Prognostic factors deduced from the primary tumor cannot predict outcome for the individual patient, whereas our approach monitoring CETC allows real-time survey of therapy response in individual patients. We confirm the observation of low responsiveness of ER+ tumors also in disseminated cells, with dormant CETC in most cases, not eliminated by current therapies but also not leading to early relapse. In contrast, most patients with CETC increasing during therapy suffer early relapse. This indicates not only that these cells are an important indicator of imminent relapse but also distant metastases may be the result of growth or regrowth of these cells. In some patients treatment influences subpopulations differently with a resistant population emerging responsible for relapse.

No significant financial relationships to disclose.

Differential interaction of magnetic nanoparticles with tumor cells and peripheral blood cells

PURPOSE

The separation of tumor cells from healthy cells is a vital problem in oncology and hematology, especially from peripheral blood. Magnetic assisted cell sorting (MACS) is a possibility to fulfill these needs.

METHODS

Tumor cell lines and leukocytes from peripheral blood were incubated with carboxymethyl dextran-coated magnetic nanoparticles under various conditions and separated by MACS.

RESULTS

We studied the interaction of magnetic nanoparticles devoid of antibodies with healthy and tumor cells. The magnetic nanoparticles interact with tumor cells and leukocytes and are located predominantly within the cell cytoplasm. Incubation of cell culture cells with magnetic nanoparticles led to a labeling of these cells without reduced biological properties for at least 14 days. The interaction of the magnetic nanoparticles with cells depends on several factors. The ionic strength (osmolality) of the solvent plays an important role. We could show that an increase in osmolality led to a dramatic reduction of labeled leukocytes. Tumor cells, however, are mildly affected. This could be detected not only in pure cultures of tumor cells or leukocytes but also in mixed cell populations.

CONCLUSION

This observation gives us the opportunity to selectively label and separate tumor cells but not leukocytes from the peripheral blood.

Impact of early NK cell recovery on development of GvHD and CMV reactivation in dose-reduced regimen prior to allogeneic PBSCT

Dose-reduced allogeneic peripheral blood stem cell transplantation (PBSCT) is a therapeutic approach for patients with haematological malignancies who are not eligible for conventional allogeneic PBSCT. We analysed early development of lymphocyte subpopulations and the occurrence of cytomegalovirus (CMV) reactivation and acute graft-versus-host reaction (GvHD) in patients undergoing the protocol according to Slavin vs conventionally treated patients. Lymphocyte status prior to conditioning and at day +30 after allogeneic PBSCT was determined in 24 out of 51 patients who received conventional allogeneic PBSCT (eg cyclophosphamide plus total body irradiation) and compared with 27 patients being treated according to the Slavin protocol (fludarabine, busulphan and ATG). There is a significant delay in CD4 (T helper) cell development and consecutive lower CD4/CD8 ratios and a better reconstitution of CD8 (T cytotoxic) and NK (natural killer) cells after the Slavin protocol. Patients undergoing this protocol and no, or only grade I, acute GvHD show an even better NK cell reconstitution compared to patients with grade II-IV GvHD. A low CD4/CD8 ratio represents a CMV risk factor only in conventionally treated patients with grade 0-I GvHD, while after preparative regimen according to the Slavin protocol, the NK/CD8 ratio might be a marker for the prediction of CMV reactivation in addition to CMV risk status.

Detection and quantification of small numbers of circulating tumour cells in peripheral blood using laser scanning cytometer (LSC)

The detection of circulating tumour cells disseminated from solid tumours requires extremely sensitive methods. Molecular genetic methods, which are most sensitive, are not applicable to solid tumours because no tumour-specific genetic markers are available. Detection of disseminated tumour cells by immunocytochemistry is time-consuming, whereas fluorimetry is fast and quantitative. The laser scanning cytometer (LSC) provides an automated microscopic procedure for screening up to 5x10(4) cells in suitable time. Using this system together with an enrichment procedure which allows up to ten thousand-fold enrichment, we have quantified minimal numbers of tumour cells. In a model system, breast cancer cell line cells diluted into peripheral blood mimicked seeding of tumour cells into the periphery. After staining with fluorochrome-conjugated anti-epithelial antibody, slides were screened for positive events directly or after enrichment with antibody-coated magnetic beads. One positive cell was unequivocally detectable in 10(4) cells and 50 out of 60 tumour cells were reliably recovered from a 20 ml blood volume, equal to 1-2 cells per 10(7), after magnetic bead enrichment. This method allows quantitation of tumour cells in peripheral blood and bone marrow in reasonable time and will, for the first time, enable extensive investigation of the seeding behaviour of tumours.

Expression of bcr-abl mRNA in individual chronic myelogenous leukaemia cells as determined by in situ amplification

We present the results of a novel method developed for evaluation of in situ amplification, a molecular genetic method at the cellular level. Reverse transcription polymerase chain reaction (RT-PCR) was used to study bcr-abl transcript levels in individual cells from patients with chronic myelogenous leukaemia (CML). After hybridizing a fluorochrome-labelled probe to the cell-bound RT-PCR product, bcr-abl mRNA-positive cells were determined using image analysis. A dilution series of bcr-abl-positive BV173 into normal cells showed a good correlation between expected and actual values. In 25 CML samples, the percentage of in situ PCR-positive cells showed an excellent correlation with cytogenetic results (r = 0.94, P < 0.0001), interphase fluorescence in situ hybridization (FISH) (r = 0.95, P = 0.001) and hypermetaphase FISH (r = 0.81, P < 0.001). The fluorescence intensity was higher in residual CML cells after interferon (IFN) treatment than in newly diagnosed patients (P = 0.004), and was highest in late-stage CML resistant to IFN therapy and lowest in CML blast crisis (P = 0.001). Mean fluorescence values correlated with bcr-abl protein levels, as determined by Western blot analysis (r = 0.62). Laser scanning cytometry allowing automated analysis of large numbers of cells confirmed the results. Thus, fluorescence in situ PCR provides a novel and quantitative approach for monitoring tumour load and bcr-abl transcript levels in CML.

Complementary anchor PCR of rearranged variable T-cell receptor beta-chain cDNA regions

Sequencible amplificates comprising the variable cDNA sequences of the rearranged T-cell receptor (TCR) beta-chain were obtained from the T-leukemia cell line Jurkat using a single-sided PCR approach based on five synthetic oligonucleotides derived from the flanking constant sequence. Double-stranded cDNA was cleaved by a restriction enzyme creating cohesive ends, to which an anchor oligonucleotide was ligated. Since this anchor was complementary to the antisense strand of the known constant region, exclusively the desired ligation product folded into a stem-loop-structure that was enzymatically extended to yield a PCR template, now flanked at both ends by primer binding sites appropriate for nested PCR.

Applications of consensus polymerase chain reaction with subsequent electrophoretic distinction of amplificates

Conserved sequences within gene families permit the design of consensus primers that match several members of a given class of homologous genes. Polymerase chain reaction (PCR) products obtained with such consensus primers were characterized by restriction mapping or single-strand conformation polymorphism (SSCP) analysis, using precast polyacrylamide minigels and automated silver staining. Examples for the electrophoretic distinction of consensus amplificates are presented in the fields of guanylyl cyclase expression studies and in the determination of B-cell clonality in human blood samples. Guanylyl cyclase expression in inner ear tissues of guinea pigs was investigated by reverse transcription PCR using consensus primers with specificity for the subclass of particulate guanylyl cyclases. The resulting PCR products were assigned to three representatives of this group by restriction mapping. The consensus PCR approach enabled the detection of an unexpected receptor type, namely guanylyl cyclase C, in the inner ear. The distinction by SSCP analysis of denatured consensus amplificates was appropriate for the identification of clone-specifically rearranged immunoglobulin heavy chain genes of B-lymphocytes. Genomic DNA isolated from blood samples of leukemia patients served as the template for the consensus amplification of clone-specific VDJ rearrangements. Rapid distinction and re-identification of consensus PCR products was achieved by SSCP analysis for regular antigen receptor rearrangements and for t(14; 18) translocations. The potential of these procedures for detecting leukemia or lymphoma clones when monitoring minimal residual disease was assessed.

Insulin-like growth factor I is an independent coregulatory modulator of natural killer (NK) cell activity

We aimed to investigate the natural killer (NK) cell activity in hGH-deficient adults and to analyze the effect of insulin-like growth factor (IGF)-I in vivo and in vitro on NK cell activity. NK cell activity was measured in a 4-h nonisotopic assay with europium-labeled and cryopreserved K-562 cells. NK-cell numbers were measured after incubation with murine monoclonal CD3 and CD16 antibodies by flow cytometry analysis. In a cross-sectional study, the basal and interferon-beta (IFN-beta) stimulated (1000 IU/ml) NK cell activity of 15 hGH-deficient patients and 15 age- and sex-matched controls was measured. The percentages and absolute numbers of CD3-/16+ NK-cells were not significantly different in the patient vs. control group. The basal and IFN-beta stimulated NK cell activity however was significantly decreased in the patient vs. control group at all effector/target (E/T) cell ratios from 12.5-100 (e.g. 17 +/- 3 vs. 28 +/- 3% lysis without IFN-beta, P < 0.05, and 42 +/- 4 vs. 57 +/- 4% lysis with IFN-beta, P < 0.05; both at E/T 50). IGF-I levels of patients and controls showed a significant positive correlation with NK cell activity (r = 0.37; P < 0.05). In an IGF-I in vitro study (IGF-I in vitro 250-1250 microg/L), the basal and IFN-beta stimulated NK cell activity of 13 hGH-deficient patients and of 18 normal subjects was significantly enhanced by IGF-I in vitro (e.g. GH-deficient patients: 9 +/- 2 vs. 10 +/- 2% lysis without IFN-beta, P < 0.05 and 25 +/- 4 vs. 30 +/- 4% lysis with IFN-beta, P < 0.005; and normal subjects: 15 +/- 3 vs. 23 +/- 3% lysis without IFN-beta, P < 0.001 and 35 +/- 4 vs. 44 +/- 5% lysis with IFN-beta, P < 0.001; both at IGF-I 500 microg/L). In summary, in our cross-sectional study, adult GH-deficient patients showed a significantly lower basal and IFN-beta stimulated NK cell activity than matched controls, despite equal NK cell numbers. IGF-I levels of patients and controls showed a weak positive correlation with NK cell activity. In an in vitro study, IGF-I significantly enhanced basal and IFN-beta stimulated NK cell activity of hGH-deficient patients and also of normal subjects. The decreased NK cell activity in GH-deficient patients may be caused at least in part by low serum IGF-I levels. IGF-I appears to be an independent coregulatory modulator of NK cell activity.