CLT1 targets bladder cancer through integrin α5β1 and CLIC3

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• High-grade non-muscle-invasive bladder cancer treatment often involves Bacillus Calmette-Guérin (BCG).
• BCG internalization into bladder cancer cells relies on fibronectin and integrin α5β1.
• Previous research indicated the anti-angiogenic peptide CLT1 forms cytotoxic complexes with fibronectin.

Purpose of the Study:

• To investigate the cytotoxic effects of CLT1 on various cancer cell lines, including bladder cancer.
• To elucidate the mechanism of CLT1-induced cell death, focusing on fibronectin, integrin α5β1, and chloride intracellular channel 3 (CLIC3).
• To evaluate CLT1's potential as a targeted therapy for bladder cancer.

Main Methods:

• Cytotoxicity assays were performed on multiple cancer cell lines (bladder, kidney, lung, breast, prostate).
• Mechanistic studies involved assessing fibronectin's role in CLT1 internalization and cell death.
• Integrin α5β1 and CLIC3 expression and colocalization with CLT1 in tumor tissues were analyzed.
• Fluorescence imaging was used to assess CLT1 binding to patient-derived bladder tumor tissues.

Main Results:

• CLT1 demonstrated high cytotoxicity against a range of cancer cell lines, including bladder cancer.
• Fibronectin enhanced CLT1-induced tumor cell death by mediating internalization and triggering autophagic cell death.
• The mechanism of CLT1 action depends on tumor cell integrin α5β1 and CLIC3, which were upregulated in responsive cell lines.
• CLT1 showed strong and specific fluorescence in bladder cancer patient tissues, but not in normal bladder tissue.

Conclusions:

• CLT1 exhibits potent cytotoxic effects on various cancer cells, notably bladder cancer.
• CLT1 utilizes fibronectin, integrin α5β1, and CLIC3 for internalization and induction of autophagic cell death.
• CLT1 demonstrates specific affinity for bladder tumor tissue, suggesting its potential as a targeted therapeutic agent for bladder cancer.