Weiterentwicklung eines neuen therapeutischen Ansatzes gegen Brustkrebs mittels SFRP1-Mimetika und Untersuchung des potentiellen Zusammenhangs von SFRP1 und AR im humanen Brustkrebs

  • Further development of a new therapeutic approach against breast cancer using SFRP1 mimetics and investigation of the potential relationship between SFRP1 and AR in human breast cancer

Villwock, Sophia; Weinhold, Elmar (Thesis advisor); Dahl, Edgar (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022


The main objective of this work was to continue a proof-of-concept phase for a new therapeutic approach in personalized breast cancer therapy, based on the development of small molecule compounds as a replacement (mimetic) for the tumor suppressor protein SFRP1 lost in the tumor. Furthermore, this work describes for the first time a possible regulatory interaction of the androgen receptor (AR), which is expressed in many breast tumors, with this same tumor suppressor SFRP1.The activated Wnt/β-catenin signaling pathway plays an important role in the development and progression of various tumor diseases such as breast cancer and pancreatic cancer. The tumor suppressor SFRP1 is a negative regulator of this pathway and thus an important antagonist that can suppress tumorigenesis and tumor growth. Indeed, SFRP1 protein expression is lost in many solid tumors by promoter DNA methylation, which is why this gene is also one of the epigenetically regulated class 2 tumor suppressor genes. Since SFRP1 is already well studied and understood in this pathway, it is suitable for a new mechanism-based approach to find tumor therapeutically active compounds in the context of drug screening. In this work, a new approach based on functional screening of a cellular breast cancer model for the discovery and development of SFRP1 mimetics was further pursued in cooperation with the Lead Discovery Center (LDC, Dortmund, Germany). In such a functional screen, no precise target structure is addressed, but the entire SFRP1-dependent Wnt/β-catenin signaling pathway. Therefore, the aim of this work was to screen potential SFRP1 mimetics for their inhibitory mechanism of action in the Wnt/β-catenin pathway. Indeed, application of two chemically different mimetic compounds in a cellular breast cancer model caused downregulation of the β-catenin-dependent transcription factor CyclinD1, indicative of an inactivated Wnt/β-catenin signaling pathway and thus also proof-of-concept of this novel approach to drug development of SFRP1 mimetics. It was also shown that in addition to a known Wnt inhibitor (ICG-001) whose mechanism of action is based on inhibition of β-catenin-dependent transcription, the two chemically distinct SFRP1 mimetic candidates investigated may also have different mechanisms of action. Within cell culture models of triple-negative breast tumors (TNBC), the potential SFRP1 mimetics showed the strongest tumor suppressive properties in the so-called luminal androgen receptor (LAR) type, so this subtype may be particularly well suited for therapeutic application of SFRP1 mimetics. The longer-term goal is to apply this targeted therapy in additional Wnt/β-catenin-dependent entities. For example, possible therapeutic potential has already been demonstrated in vitro by growth inhibition in several pancreatic cancer cell lines.In prostate cancer, a molecular link between SFRP1 and AR has already been described, namely SFRP1 antagonizes AR here and thus reduces tumor cell growth. In breast cancer, AR also plays an important role alongside other steroid receptors such as ER and PR, but no link between AR and SFRP1 has yet been described. In this work, a possible link between the two molecules was first investigated by database analyses (in silico) and then further in cell culture experiments. The in silico analyses have shown for the first time that in breast cancer there is a possible anti-correlated relationship between SFRP1 mRNA- and AR mRNA-expression and that the SFRP1high/ARlow factor is a good prognostic factor and a possible independent factor in addition to the standard prognostic factors in the clinic. To investigate the potential molecular and functional relationship of SFRP1 and AR, an androgen-dependent breast cancer model (MDA-MB-453, LAR type) and an androgen-independent breast cancer model (Hs578T, TNBC type) with forced SFRP1 re-expression were generated. The in vitro data did not suggest clear evidence of a potential antagonistic relationship between SFRP1 and AR. However, the hypothesis could not be clearly refuted either and should be analyzed by additional models in the future.