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PD Dr. Monika Pizon (left side) and Prof. Dr. med. Katharina Pachmann (right side) attending the annual meeting of the AACR.

At this year’s annual meeting of the American Association for Cancer Research (AACR), held from April 25th to 30th, 2025, in Chigaco, USA, Pachmann GmbH & Co. KG, Simfo GmbH presented current research findings in three poster presentations on circulating tumor cells and cancer stem cells. Professor Dr. Pachmann and PD Dr. Monika Pizon engaged in numerous valuable discussions with international colleagues from medicine and science. These exchanges led to new insights and approaches in cancer diagnostics and personalized therapy. The following abstracts and posters were presented at the AACR 2025 Annual Meeting in Chicago, USA:

"Immune regulatory molecule expression on circulating tumor cells and circulating cancer stem cells in breast cancer patients"

Monika Pizon, Dorothea Schott, Erika Schill, Ulrich Pachmann, Katharina Pachmann; Abstract 1938: Immune regulatory molecule expression on circulating tumor cells and circulating cancer stem cells in breast cancer patients. Cancer Res 15 April 2025; 85 (8_Supplement_1): 1938. https://doi.org/10.1158/1538-7445.AM2025-1938

In this study, circulating epithelial tumor cells (CETCs/CTCs) and circulating cancer stem cells (cCSCs) from 80 breast cancer patients were analyzed for the expression of the immune checkpoint molecules PD-L1 and CTLA-4. The aim was to investigate their role in immune evasion and their potential as markers for predicting the success of immunotherapies. CETCs/CTCs were detected in all patients, with particularly high PD-L1 expression observed in cases of triple-negative breast cancer. CTLA-4 expression was generally lower. The number of tumorspheres increased with tumor progression and the aggressiveness of the primary tumor. All tumorspheres expressed both PD-L1 and CTLA-4, although with substantial heterogeneity in expression levels.

"How circulating tumor cells disguise"

Dorothea Schott, Monika Pizon, Andreas Riess, Katharina Pachmann; Abstract 1937: How circulating tumor cells disguise. Cancer Res 15 April 2025; 85 (8_Supplement_1): 1937. https://doi.org/10.1158/1538-7445.AM2025-1937

Metastasis represents the greatest threat posed by malignant tumors and often occurs months to years after the removal of the primary tumor. Circulating tumor cells (CETCs/CTCs) are considered the origin of these metastases but are often no longer detectable immediately after surgery. Using the maintrac®-method, it was shown that CETCs/CTCs remain present in the blood in cases of both lung and breast cancer, but are initially undetectable due to masking by attached platelets. Only after 24 hours of sample storage at room temperature did the platelets detach from the cells, enabling EpCAM-based detection.

"Circulating epithelial tumor cells as a biomarker to predict treatment failure of radiotherapy in breast and prostate cancer"

Dorothea Schott, Matthias Maurer, Monika Pizon, Katharina Pachmann; Abstract 1936: Circulating epithelial tumor cells as a biomarker to predict treatment failure of radiotherapy in breast and prostate cancer. Cancer Res 15 April 2025; 85 (8_Supplement_1): 1936. https://doi.org/10.1158/1538-7445.AM2025-1936

Radiotherapy is a central component in the treatment of breast and prostate cancer. While local recurrences are effectively reduced, distant relapses still occur. In this study, the maintrac®-method was used to analyze the number and characteristics of circulating epithelial tumor cells (CETCs/CTCs) during radiotherapy to identify potential biomarkers for an increased risk of metastasis. An increase in cell numbers in breast cancer patients, particularly after neoadjuvant therapy, was associated with a higher risk of relapse. Similarly, in prostate cancer, a rise in CETC/CTC counts during radiotherapy indicated an increased risk of recurrence, although not all patients with rising cell numbers experienced relapse. Additionally, an increase in PD-L1 expression on CETCs/CTCs over the course of radiotherapy correlated with the occurrence of relapses.