PIP₃ abundance overcomes PI3K signaling selectivity in invadopodia

Area of Science:

• Cell Biology
• Cancer Research
• Biochemistry

Background:

• Invadopodia are critical for cancer cell invasion and metastasis.
• Phosphoinositide 3-kinases (PI3Ks) play a key role in cell signaling pathways, including those involved in cancer progression.
• PI3Kβ is known to be essential for invadopodia-mediated matrix degradation in breast cancer cells.

Purpose of the Study:

• To investigate whether PI3Kβ selectivity is maintained under conditions of increased PI3K activity due to mutations.
• To explore the role of specific phosphoinositide products in invadopodia function.
• To understand the compensatory mechanisms within the PI3K pathway in breast cancer cells.

Main Methods:

• Utilized breast cancer cell models with inhibited PI3Kβ.
• Employed short-chain phosphoinositides (diC8-PIP3 and diC8-PI(3,4)P2) to rescue gelatin degradation.
• Introduced activated PI3Kβ and PI3Kα mutants to assess their impact on invadopodia function and SHIP2 dependence.

Main Results:

• PI3Kβ inhibition impaired gelatin degradation, which could be rescued by diC8-PIP3 in a SHIP2-dependent manner.
• Rescue by diC8-PI(3,4)P2 was SHIP2-independent.
• Expression of activated PI3Kβ or PI3Kα mutants rescued PI3Kβ inhibition effects, with both requiring SHIP2 for gelatin degradation.

Conclusions:

• The conversion of PIP3 to PI(3,4)P2 is essential for invadopodia function.
• Mutational activation of the PI3K pathway can overcome the need for PI3Kβ selectivity.
• These findings suggest potential therapeutic strategies targeting the PI3K pathway in breast cancer.