Ph. D. Project
Title:
Exploration of the genetic material of small extracellular vesicles and their involvement in the development of metastases.
Dates:
2025/12/01 - 2028/11/30
Supervisor(s):
Other supervisor(s):
DARDARE Julie (j.dardare@nancy.unicancer.fr)
Description:
Extracellular vesicles (EVs) are defined by the International Society for Extracellular Vesicles (ISEV) as particles released
by cells, bounded by a lipid bilayer, and unable to replicate (1). EVs can be differentiated based on their size as "large EVs"
(>200 nm) or "small EVs" (<200 nm). The latter are subdivided into several subtypes, including microvesicles, exosomes,
and ectosomes. EVs are secreted by all cell types and are found in all body fluids. They expose and contain numerous
molecules such as proteins, lipids, metabolites, and nucleic acids. Once released into the extracellular environment, EVs can
be internalized by surrounding or distant recipient cells. They thus play a major role in intercellular communication by
triggering various biological responses dependent on the released content (2).
EVs are actively produced by cancer cells. Indeed, the hypoxic and acidic environment within the tumor induces cellular
stress that promotes their secretion. These tumor-derived EVs transport various cancer cell components, such as signaling
pathway activating factors and genetic material (RNA, DNA, miRNA). The transfer of this content to recipient cells can lead
to the reprogramming of their genome and proteome, promoting the acquisition of new cellular functions that contribute to
tumor progression (3). EVs are notably involved in tumor microenvironment remodeling, angiogenesis, treatment resistance,
and the metastasis process.
Numerous studies have demonstrated the involvement of EVs in treatment response. It has been shown that chemotherapy
and/or radiotherapy treatment can not only increase the biogenesis and secretion of EVs from tumor cells, but can also
modify their content.
Various mechanisms of chemotherapy resistance induced by EVs have been reported, such as increased efflux of
chemotherapies, reduced toxicity, and improved DNA repair (4). In the case of radiotherapy treatment, EVs are involved in
the activation of DNA repair pathways, cell proliferation, inhibition of apoptosis in irradiated cells, and transmission of
genomic instability from these cells to neighboring cells (5). These data reinforce the idea of ??taking into account the impact
of treatments on EVs in order to understand their involvement in disease progression.
Metastasis is the leading cause of cancer-related mortality. It is traditionally described as a process involving the detachment
of cells from a primary tumor, their migration through the bloodstream, and their implantation in metastatic sites. Although
this model is well established, only 0.01% of cancer cells found in the circulation will ultimately form metastases (6),
suggesting that this biological mechanism likely coexists with others. A more recent theory called "genometastasis" provides
new insights into the onset of metastasis. This theory suggests that small fragments of circulating cell-free DNA from the
tumor could be integrated through horizontal gene transfer and lead to the transformation of distant healthy cells to form
metastases (7,8). Despite the lack of understanding of the mechanisms involved to date, the involvement of tumor-derived
EVs in metastasis has been repeatedly suggested. It has been observed that EVs, particularly exosomes, can transport
oncogenic factors into the plasma of patients even at precancerous stages (9⬓11). Furthermore, several studies have
demonstrated the ability of EVs isolated from cancer patients to induce malignant transformation of healthy recipient cells.
These various studies agree that, to be transformed, healthy cells must be "initiated" either by the mutation of at least one
oncogene, via treatment with a carcinogenic agent, or by immortalization of the recipient cell line (9⬓14). Although the
transformation of recipient cells has been well described, many questions remain regarding the content of EVs and the
molecular mechanisms involved in this malignant transformation. Some studies report the presence of single-stranded DNA
reflecting the tumor's genetic status (15), others the presence of long double-stranded DNA fragments representative of the
entire genomic DNA (16,17), while some claim that small EVs do not contain DNA (18). Furthermore, some studies report
the presence of DNA in the lumen of EVs (16,17), while others suggest that DNA is primarily associated with the EV
surface (19). Finally, few studies have focused on exploring the DNA contained in EVs, and their results are still debated. In
this context, our objective is to characterize the genetic material contained in small EVs isolated from tumor cell lines,
before and after chemotherapy or radiotherapy treatment. Furthermore, we
wish to explore the effect of these EVs upon contact with healthy cells in order to decipher the molecular mechanisms
associated with malignant transformation and the development of metastases.
by cells, bounded by a lipid bilayer, and unable to replicate (1). EVs can be differentiated based on their size as "large EVs"
(>200 nm) or "small EVs" (<200 nm). The latter are subdivided into several subtypes, including microvesicles, exosomes,
and ectosomes. EVs are secreted by all cell types and are found in all body fluids. They expose and contain numerous
molecules such as proteins, lipids, metabolites, and nucleic acids. Once released into the extracellular environment, EVs can
be internalized by surrounding or distant recipient cells. They thus play a major role in intercellular communication by
triggering various biological responses dependent on the released content (2).
EVs are actively produced by cancer cells. Indeed, the hypoxic and acidic environment within the tumor induces cellular
stress that promotes their secretion. These tumor-derived EVs transport various cancer cell components, such as signaling
pathway activating factors and genetic material (RNA, DNA, miRNA). The transfer of this content to recipient cells can lead
to the reprogramming of their genome and proteome, promoting the acquisition of new cellular functions that contribute to
tumor progression (3). EVs are notably involved in tumor microenvironment remodeling, angiogenesis, treatment resistance,
and the metastasis process.
Numerous studies have demonstrated the involvement of EVs in treatment response. It has been shown that chemotherapy
and/or radiotherapy treatment can not only increase the biogenesis and secretion of EVs from tumor cells, but can also
modify their content.
Various mechanisms of chemotherapy resistance induced by EVs have been reported, such as increased efflux of
chemotherapies, reduced toxicity, and improved DNA repair (4). In the case of radiotherapy treatment, EVs are involved in
the activation of DNA repair pathways, cell proliferation, inhibition of apoptosis in irradiated cells, and transmission of
genomic instability from these cells to neighboring cells (5). These data reinforce the idea of ??taking into account the impact
of treatments on EVs in order to understand their involvement in disease progression.
Metastasis is the leading cause of cancer-related mortality. It is traditionally described as a process involving the detachment
of cells from a primary tumor, their migration through the bloodstream, and their implantation in metastatic sites. Although
this model is well established, only 0.01% of cancer cells found in the circulation will ultimately form metastases (6),
suggesting that this biological mechanism likely coexists with others. A more recent theory called "genometastasis" provides
new insights into the onset of metastasis. This theory suggests that small fragments of circulating cell-free DNA from the
tumor could be integrated through horizontal gene transfer and lead to the transformation of distant healthy cells to form
metastases (7,8). Despite the lack of understanding of the mechanisms involved to date, the involvement of tumor-derived
EVs in metastasis has been repeatedly suggested. It has been observed that EVs, particularly exosomes, can transport
oncogenic factors into the plasma of patients even at precancerous stages (9⬓11). Furthermore, several studies have
demonstrated the ability of EVs isolated from cancer patients to induce malignant transformation of healthy recipient cells.
These various studies agree that, to be transformed, healthy cells must be "initiated" either by the mutation of at least one
oncogene, via treatment with a carcinogenic agent, or by immortalization of the recipient cell line (9⬓14). Although the
transformation of recipient cells has been well described, many questions remain regarding the content of EVs and the
molecular mechanisms involved in this malignant transformation. Some studies report the presence of single-stranded DNA
reflecting the tumor's genetic status (15), others the presence of long double-stranded DNA fragments representative of the
entire genomic DNA (16,17), while some claim that small EVs do not contain DNA (18). Furthermore, some studies report
the presence of DNA in the lumen of EVs (16,17), while others suggest that DNA is primarily associated with the EV
surface (19). Finally, few studies have focused on exploring the DNA contained in EVs, and their results are still debated. In
this context, our objective is to characterize the genetic material contained in small EVs isolated from tumor cell lines,
before and after chemotherapy or radiotherapy treatment. Furthermore, we
wish to explore the effect of these EVs upon contact with healthy cells in order to decipher the molecular mechanisms
associated with malignant transformation and the development of metastases.
Keywords:
extracellulare vesicles, metastasis
Conditions:
Validated Master degree, knowledge and skills in molecular biology and cells culture
Department(s):
| Biology, Signals and Systems in Cancer and Neuroscience |
Funds:
Doctoral contract in private law (funded by a non-profit private health institution)