The Intracellular Delivery of a Recombinant Peptide Derived from the Acidic Domain of PIAS3 Inhibits STAT3 Transactivation and Induces Tumor Cell Death

Abstract

Signaling components, which confer an "addiction" phenotype on cancer cells, represent promising drug targets. The transcription factor signal transducers and activators of transcription 3 (STAT3) is constitutively activated in many different types of tumor cells and its activity is indispensible in a large fraction. We found that the expression of the endogenous inhibitor of STAT3, protein inhibitor of activated STAT3 (PIAS3), positively correlates with STAT3 activation in normal cells. This suggests that PIAS3 controls the extent and the duration of STAT3 activity in normal cells and thus prevents its oncogenic function. In cancer cells, however, the expression of PIAS3 is posttranscriptionally suppressed, possibly enhancing the oncogenic effects of activated STAT3. We delimited the interacting domains of STAT3 and PIAS3 and identified a short fragment of the COOH-terminal acidic region of PIAS3, which binds strongly to the coiled-coil domain of STAT3. This PIAS3 fragment was used to derive the recombinant STAT3-specific inhibitor rPP-C8. The addition of a protein transduction domain allowed the efficient internalization of rPP-C8 into cancer cells. This resulted in the suppression of STAT3 target gene expression, in the inhibition of migration and proliferation, and in the induction of apoptosis at low concentrations [half maximal effective concentration (EC 50 ), <3 μmol/L]. rPP-C8 did not affect normal fibroblasts and represents an interesting lead for the development of novel cancer drugs targeting the coiled-coil domain of STAT3. Mol Cancer Res; 8(4); 539-53. ©2010 AACR.

Low PIAS3 Expression in Malignant Mesothelioma Is Associated with Increased STAT3 Activation and Poor Patient Survival

“…STAT3 inhibition can also be affected by peptides (5,17,38). Our study indicates that the uptake of a STAT3-inhibiting peptide into mesothelioma cells is effective and induces cell growth inhibition and apoptosis.…”

“…Protein purification of the peptide rPP-C8 and cell treatment was performed as described previously (17). Briefly, 2,000 cells were seeded in 96-well plates, and the next day, medium was removed, 0.5 or 2.0 mmol/L of the peptide (or PBS as solvent control) was diluted in 100 mL medium and added to the cells.…”

“…It has recently been shown that rPP-C8, a C-terminal recombinant peptide derived from PIAS3, has the ability to inhibit STAT3 activity and cell growth in glioblastoma cells (17). The peptide is able to penetrate the plasma membrane upon addition to the growth medium.…”

A positive feedback loop between miR‐181b and STAT3 that affects Warburg effect in colon cancer via regulating PIAS3 expression

“…L97 and R99 are part of a potential binding surface and mutations of L97 and R99 of the PINIT domain abrogate binding to STAT3 39. In addition, the acidic region of the carboxyl terminal of PIAS3 can specifically bind to the rPP‐C8 region of STAT3, thereby inhibiting the proliferation and promoting the apoptosis of tumour cells 40. Therefore, miR‐181b might inhibit the expression of PIAS3 and directly bind to the PINIT domain of PIAS3 (PIAS3 82‐132 , PIAS3 85‐272 , and/or L97&R99).…”

Increasing the range of drug targets

“…Intravenous administration of rS3-PA into mice showed that the systemic application of rS3-PA inhibits Stat3 activation in vivo and slightly retarded the growth kinetics of transplanted glioma cells. 13 An alternative strategy was used to derive a survivin inhibiting molecule. A cDNA library was screened in a yeast two-hybrid setting for survivin-interacting proteins.…”