Expressed cell-penetrating peptides can induce a bystander effect, but passage through the secretory pathway reduces...

Area of Science:

• Biotechnology
• Molecular Biology
• Cancer Research

Background:

• Inefficient gene transfer hinders cancer gene therapy efficacy.
• Cell-penetrating peptides (CPPs), like HIV-1 Tat, facilitate cellular uptake of proteins.
• Combining gene therapy with protein transduction offers potential for targeted protein delivery and bystander effects.

Purpose of the Study:

• To investigate if expressed CPPs, specifically Tat-fusion proteins, can mediate intercellular trafficking and induce a bystander effect.
• To determine the role of secretory signal peptides (SP) in the bystander effect of Tat-fusion proteins.
• To explore the mechanisms underlying protein transduction mediated by Tat-fusion proteins.

Main Methods:

• Construction and expression of Tat-fusion proteins with and without a secretory signal peptide (SP).
• Assessment of intercellular trafficking and bystander effect in vitro and in vivo.
• Analysis of protein secretion and cell lysis-mediated release.

Main Results:

• Expressed Tat-fusion proteins lacking an SP did not induce a detectable bystander effect.
• Tat-fusion proteins with an SP induced a modest in vitro bystander effect, but minimal in vivo effect.
• The bystander effect was not directly correlated with protein secretion; inefficient secretion and cell lysis were primary contributors to protein transduction.
• Modifications to improve secretion reduced transduction activity.

Conclusions:

• Expressed Tat-fusion proteins alone are insufficient to mediate a significant bystander effect.
• While SP-containing Tat-fusion proteins show some intercellular trafficking, the mechanism is complex and not solely dependent on secretion.
• Cell lysis plays a crucial role in releasing functional Tat-fusion proteins for transduction, suggesting alternative strategies for enhancing cancer gene therapy efficacy.