Cancer Stem Cells, MicroRNAs & Therapeutic strategies including Stem Cell Microparticles
Date Issued
June 23, 2014
Abstract
Introduction: In recent years, the cancer stem cell (CSC) model has been suggested
to explain the functional heterogeneity and the carcinogenesis process of cancer.
CSCs have the ability to initiate and sustain tumor growth, metastasis and
resistance to therapy.
MicroRNAs (miRNAs) are small non-coding RNA molecules, which function in
transcriptional and post-transcriptional regulation of gene expression. Aberrant
expression of miRNAs has been implicated in numerous diseases including some if
not all cancer types. Recent findings suggest that miRNAs could be involved in
maintaining and regulating the stemness of CSCs. Therefore, miRNAs have been
proposed as attractive targets for therapy and miRNA-related therapeutic
strategies are under investigation. However, systemic delivery of miRNAs faces its
own set of limitations because miRNAs may be degraded in the blood by enzymes
such as RNases and excreted by the kidneys.
In this work we propose a novel system for therapeutic miRNA delivery applicable
for both local and systemic administration with the use of umbilical cord
mesenchymal stem cell (MSC) microparticles (MPs).
Methodology: MSCs were isolated from the Wharton’s jelly of human umbilical
cords. The MSC cultures were subjected to stress conditions, leading to the
formation of MPs (secreted membrane vehicles <1μm) which were harvested and
characterized by SEM, PCR, FACS and Fluorescence Microscopy. Breast (MDA-MB231 & MCF-7), colon (RKO & HT-29) and ovarian adenocarcinoma (SKOV3) cell lines were then exposed to MPs. The response to treatment was evaluated by cell
morphology, proliferation, migration, gene expression and apoptosis.
Furthermore, the therapeutic potential of MPs was tested in vivo in xenograft
tumor mouse models. Innovative imaging modalities such as in vivo flow cytometry
and whole body fluorescence-bioluminescence were employed to dynamically
investigate the biodistribution and homing kinetics of MPs in mice.
Results: In vitro experiments confirmed that MSC-derived MPs can be internalised
by the various cancer cell lines and induce a biological effect as evidenced by
membrane damage, cell shrinkage and blebbing in the recipient cell. Significantly,
there was evidence that MPs induce apoptosis, inhibit cell proliferation and
mediate tumor growth attenuation in a dose/time-dependent manner. The proapoptotic and anti-migrating effects of MPs in cancer cells were almost completely
abrogated by RNase treatment before administration to cultures. Preliminary in
vivo studies demonstrated that we were able to monitor and quantify fluorescently
labelled MPs in circulation and to detect and image the biodistribution and
incorporation in cells and organs in healthy and tumor-bearing mice.
Conclusion: MSC-derived MPs containing miRNAs possess tumor inhibitory
properties both in vitro and in vivo. Administration of MPs after RNase treatment
induces the loss of anti-cancer properties suggesting a horizontal transfer of small
RNAs from MPs to cancer cells. MPs formulated to contain specific miRNAs, could
affect the action of genes associated with carcinogenesis, neovascularization,
metastasis and other cancer characteristics leading to therapeutic benefit.
to explain the functional heterogeneity and the carcinogenesis process of cancer.
CSCs have the ability to initiate and sustain tumor growth, metastasis and
resistance to therapy.
MicroRNAs (miRNAs) are small non-coding RNA molecules, which function in
transcriptional and post-transcriptional regulation of gene expression. Aberrant
expression of miRNAs has been implicated in numerous diseases including some if
not all cancer types. Recent findings suggest that miRNAs could be involved in
maintaining and regulating the stemness of CSCs. Therefore, miRNAs have been
proposed as attractive targets for therapy and miRNA-related therapeutic
strategies are under investigation. However, systemic delivery of miRNAs faces its
own set of limitations because miRNAs may be degraded in the blood by enzymes
such as RNases and excreted by the kidneys.
In this work we propose a novel system for therapeutic miRNA delivery applicable
for both local and systemic administration with the use of umbilical cord
mesenchymal stem cell (MSC) microparticles (MPs).
Methodology: MSCs were isolated from the Wharton’s jelly of human umbilical
cords. The MSC cultures were subjected to stress conditions, leading to the
formation of MPs (secreted membrane vehicles <1μm) which were harvested and
characterized by SEM, PCR, FACS and Fluorescence Microscopy. Breast (MDA-MB231 & MCF-7), colon (RKO & HT-29) and ovarian adenocarcinoma (SKOV3) cell lines were then exposed to MPs. The response to treatment was evaluated by cell
morphology, proliferation, migration, gene expression and apoptosis.
Furthermore, the therapeutic potential of MPs was tested in vivo in xenograft
tumor mouse models. Innovative imaging modalities such as in vivo flow cytometry
and whole body fluorescence-bioluminescence were employed to dynamically
investigate the biodistribution and homing kinetics of MPs in mice.
Results: In vitro experiments confirmed that MSC-derived MPs can be internalised
by the various cancer cell lines and induce a biological effect as evidenced by
membrane damage, cell shrinkage and blebbing in the recipient cell. Significantly,
there was evidence that MPs induce apoptosis, inhibit cell proliferation and
mediate tumor growth attenuation in a dose/time-dependent manner. The proapoptotic and anti-migrating effects of MPs in cancer cells were almost completely
abrogated by RNase treatment before administration to cultures. Preliminary in
vivo studies demonstrated that we were able to monitor and quantify fluorescently
labelled MPs in circulation and to detect and image the biodistribution and
incorporation in cells and organs in healthy and tumor-bearing mice.
Conclusion: MSC-derived MPs containing miRNAs possess tumor inhibitory
properties both in vitro and in vivo. Administration of MPs after RNase treatment
induces the loss of anti-cancer properties suggesting a horizontal transfer of small
RNAs from MPs to cancer cells. MPs formulated to contain specific miRNAs, could
affect the action of genes associated with carcinogenesis, neovascularization,
metastasis and other cancer characteristics leading to therapeutic benefit.