STAT3 and neoplasm: In summary, we found that Chol-siRNA polyplexes and Chol-DsiRNA polyplexes formed with PLL[30]-PEG[5K] increase potency and efficacy against STAT3 mRNA to the same extent in primary murine syngeneic breast tumors, although Chol-DsiRNA polyplexes are more physically stable in solution over 24 h and likely increase the duration of mRNA suppression in solid tumors as the frequency of tumor-saturating doses is increased.