The Potent G-Quadruplex-Binding Compound QN-302 Downregulates S100P Gene Expression in Cells and in an In Vivo Model of Pancreatic Cancer

The naphthalene diimide compound QN-302, designed to bind to G-quadruplex DNA sequences within the promoter regions of cancer-related genes, has high anti-proliferative activity in pancreatic cancer cell lines and anti-tumor activity in several experimental models for the disease. We show here that QN-302 also causes down-regulation of the expression of the S100P gene and the S100P protein in cells and in vivo. This protein is well-established as being involved in key proliferation and motility pathways in several human cancers and has been identified as a potential biomarker in pancreatic cancer. The S100P gene contains 60 putative quadruplex-forming sequences, one of which is in the promoter region, 48 nucleotides up-stream from the transcription start site. We report biophysical and molecular modeling studies showing that this sequence forms a highly stable G-quadruplex in vitro, which is further stabilized by QN-302. We also report transcriptome analyses showing that S100P expression is highly upregulated in tissues from human pancreatic cancer tumors, compared to normal pancreas material. The extent of up-regulation is dependent on the degree of differentiation of tumor cells, with the most poorly differentiated, from more advanced disease, having the highest level of S100P expression. The experimental drug QN-302 is currently in pre-IND development (as of Q1 2023) and its ability to down-regulate S100P protein expression supports a role for this protein as a marker of therapeutic response in pancreatic cancer. These results are also consistent with the hypothesis that the S100P promoter G-quadruplex is a potential therapeutic target in pancreatic cancer at the transcriptional level for QN-302. RNA-seq analyses were performed on a set of 2 poorly differentiated, 2 more highly differentiated human pancreatic tumor samples and 3 normal pancreas tissue. The 4 PDAC RNA samples were obtained from pancreatic tumor tissues with ethical approval from the NRES Committee North-west – Liverpool Central, MREC 07/H1005/87. The normal pancreas samples were obtained commercially from OriGene Technologies GmbH Germany (Cat #: CR560569, CR562915, CR561640). Differential expression analyses were performed: 2 pooly differentiated PDAC VS 3 normal pancreatic samples and 2 more highly differentiated PDAC VS 3 normal pancreatic samples.