Targeting treatment-resistant breast cancer stem cells with FKBPL and its peptide derivative, AD-01, via the CD44 pathway.

Abstract

PURPOSE:

FK506-binding protein like (FKBPL) and its peptide derivative, AD-01, have already shown tumor growth inhibition and CD44-dependent antiangiogenic activity. Here, we explore the ability of AD-01 to target CD44-positive breast cancer stem cells (BCSC).

EXPERIMENTAL DESIGN:

Mammosphere assays and flow cytometry were used to analyze the effect of FKBPL overexpression/knockdown and AD-01 treatment ± other anticancer agents on BCSCs using breast cancer cell lines (MCF-7/MDA-231/ZR-75), primary patient samples, and xenografts. Delays in tumor initiation were evaluated in vivo. The anti-stem cell mechanisms were determined using clonogenic assays, quantitative PCR (qPCR), and immunofluorescence.

RESULTS:

AD-01 treatment was highly effective at inhibiting the BCSC population by reducing mammosphere-forming efficiency and ESA(+)/CD44(+)/CD24(-) or aldehyde dehydrogenase (ALDH)(+) cell subpopulations in vitro and tumor initiation in vivo. The ability of AD-01 to inhibit the self-renewal capacity of BCSCs was confirmed; mammospheres were completely eradicated by the third generation. The mechanism seems to be due to AD-01-mediated BCSC differentiation shown by a significant decrease in the number of holoclones and an associated increase in meroclones/paraclones; the stem cell markers, Nanog, Oct4, and Sox2, were also significantly reduced. Furthermore, we showed additive inhibitory effects when AD-01 was combined with the Notch inhibitor, DAPT. AD-01 was also able to abrogate a chemo- and radiotherapy-induced enrichment in BCSCs. Finally, FKBPL knockdown led to an increase in Nanog/Oct4/Sox2 and an increase in BCSCs, highlighting a role for endogenous FKBPL in stem cell signaling.

CONCLUSIONS:

AD-01 has dual antiangiogenic and anti-BCSC activity, which will be advantageous as this agent enters clinical trial.

• Authors: Lana McClements, Anita Yakkundi, Angelos Papaspyropoulos, Hannah Harrison, Matthew P Ablett, Puthen V Jithesh, Hayley D McKeen, Rachel Bennett, Christopher Donley, Adrien Kissenpfennig, Stuart McIntosh, Helen O McCarthy, Eric O'Neill, Robert B Clarke, Tracy Robson
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 19 Issue 14 Pg. 3881-93 (Jul 15 2013) ISSN: 1557-3265 [Electronic] United States
• PMID: 23741069 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• AD-01 peptide
• Antineoplastic Agents
• CD44 protein, human
• FKBPL protein, human
• Hyaluronan Receptors
• Receptors, Notch
• Tacrolimus Binding Proteins
• Immunophilins

Topics

• Animals
• Antineoplastic Agents (pharmacology)
• Breast Neoplasms (drug therapy, metabolism, mortality)
• Drug Resistance, Neoplasm
• Female
• Humans
• Hyaluronan Receptors (metabolism)
• Immunophilins (metabolism, pharmacology)
• MCF-7 Cells
• Mice
• Mice, SCID
• Neoplastic Stem Cells (drug effects)
• Radiation Tolerance
• Receptors, Notch (antagonists & inhibitors, metabolism)
• Signal Transduction
• Spheroids, Cellular (drug effects)
• Tacrolimus Binding Proteins
• Tumor Burden (drug effects)
• Xenograft Model Antitumor Assays