Response of Human Pancreatic Cancer Cell Xenografts to Tetraiodothyroacetic Acid Nanoparticles (Publication with Expression of Concern. See vol. 14, 2023)

Tetraiodothyroacetic acid (tetrac) and its nanoparticle formulation (Tetrac NP) act at an integrin cell surface receptor to inhibit tumor cell proliferation and tumor-related angiogenesis. Human pancreatic cancer cell (PANC-1 and MPanc96) xenografts were established in nude mice, and the effects of tetrac versus Tetrac NP on tumor growth and tumor angiogenesis were determined. The in vitro effects of tetrac and Tetrac NP were also determined by reverse transcription polymerase chain reaction or immunoblot on gene expression or gene products relevant to cell cycle arrest, apoptosis, or angiogenesis. Tetrac and Tetrac NP reduced both PANC-1 tumor mass by 45-55 % and PANC-1 tumor hemoglobin content, a marker of angiogenesis, by 50-60 % (*P < 0.05) in treated groups vs. controls by treatment day 15. Comparable results were obtained with tetrac and Tetrac NP in suppressing tumor growth and tumor angiogenesis in MPanc96 xenografts. In vitro studies showed that tetrac and Tetrac NP caused accumulation of pro-apoptotic protein BcLx-s. Tetrac NP was more effective than tetrac in increasing cellular abundance of mRNAs of pro-apoptotic p53 and p21 and anti-angiogenesis thrombospondin 1 protein in PANC-1 and MPanc96 cancer cell lines. Tetrac NP noticeably decreased expression of EGFR and of anti-apoptosis gene XIAP; tetrac did not affect EGFR and increased XIAP mRNA in both MPanc96 and PANC-1. In conclusion, tetrac or Tetrac NP effectively inhibited human pancreatic xenograft growth and tumor angiogenesis via a plasma membrane receptor that downstream modulated cellular abundance of proteins or mRNAs relevant to apoptosis and angiogenesis.