c-Src differentially regulates the functions of microtentacles and invadopodia

Area of Science:

• Cell Biology
• Cancer Research
• Biochemistry

Background:

• Metastasis involves cancer cell migration and extracellular matrix (ECM) degradation.
• Actin-based protrusions like invadopodia are crucial for these processes.
• Microtentacles (McTNs), thin tubulin-based protrusions, were observed in tumor cells, prompting comparison with invadopodia.

Purpose of the Study:

• To investigate if microtentacles (McTNs) are structural or functional analogs of invadopodia.
• To elucidate the distinct roles of McTNs and invadopodia in tumor cell behavior.
• To determine the involvement of Src kinase and Tks5 in the formation and function of McTNs and invadopodia.

Main Methods:

• Utilized MDA-MB-231 tumor cells and Src-transformed fibroblasts.
• Manipulated c-Src kinase activity (constitutively active, dominant-negative, and SU6656 inhibitor).
• Silenced Tks5 expression and analyzed F-actin, phospho-cortactin, and ECM degradation.

Main Results:

• MDA-MB-231 cells produce both invadopodia and McTNs, both containing F-actin.
• Active c-Src enhances invadopodia but suppresses McTNs; inactive c-Src or SU6656 enhances McTNs while suppressing invadopodia.
• McTNs promote capillary retention in vivo and cell re-attachment in vitro, independent of Tks5 and active Src, even when invadopodia are suppressed.

Conclusions:

• Microtentacles (McTNs) and invadopodia represent distinct cytoskeletal structures with separate functions.
• McTNs contribute to tumor cell reattachment and potentially metastasis, independent of invadopodia-mediated ECM degradation.
• Src kinase activity differentially regulates McTN and invadopodium formation, highlighting distinct regulatory pathways.