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Mesenchymal stem cells (MSCs) are an integral part of the tumor microenvironment (TME); however, their role is somewhat controversial: conflicting reports suggest that, depending on the stage of tumor development, MSCs can either support or suppress tumor growth and spread. Additionally, the influence of MSCs on drug resistance is also ambiguous. Previously, we showed that, despite MSCs proliferating significantly more slowly than cancer cells, there are chemotherapeutic drugs which proved to be similarly toxic to both cell types. Here we established 2D co-cultures and 3D co-culture spheroids from different ratios of GFP-expressing, adipose tissue-derived MSCs and A431 epidermoid carcinoma cells tagged with mCherry to investigate the effect of MSCs on cancer cell growth, survival, and drug sensitivity. We examined the cytokine secretion profile of mono- and co-cultures, explored the inner structure of the spheroids, applied MSC-(nutlin-3) and cancer cell-targeting (cisplatin) treatments separately, monitored the response with live-cell imaging and identified a new, double-fluorescent cell type emerging from these cultures. In 2D co-cultures, no effect on proliferation or drug sensitivity was observed, regardless of the changes in cytokine secretion induced by the co-culture. Conversely, 3D spheroids developed a unique internal structure consisting of MSCs, which significantly improved cancer cell survival and resilience to treatment, suggesting that physical proximity and cell-cell connections are required for MSCs to considerably affect nearby cancer cells. Our results shed light on MSC-cancer cell interactions and could help design new, better treatment options for tumors.

Mesenchymal stem cells (MSCs) or fibroblasts are one of the most abundant cell types in the tumor microenvironment (TME) exerting various anti- and pro-apoptotic effects during tumorigenesis, invasion, and drug treatment. Despite the recently discovered importance of MSCs in tumor progression and therapy, the response of these cells to chemotherapeutics compared to cancer cells is rarely investigated. A widely accepted view is that these naive MSCs have higher drug tolerance than cancer cells due to a significantly lower proliferation rate. Here, we examine the differences and similarities in the sensitivity of MSCs and cancer cells to nine diverse chemotherapy agents and show that, although MSCs have a slower cell cycle, these cells are still sensitive to various drugs. Surprisingly, MSCs showed similar sensitivity to a panel of compounds, however, suffered fewer DNA double-stranded breaks, did not enter into a senescent state, and was virtually incapable of apoptosis. Our results suggest that MSCs and cancer cells have different cell fates after drug treatment, and this could influence therapy outcome. These findings could help design drug combinations targeting both MSCs and cancer cells in the TME.

The role of extracellular vesicles (EVs) in mediating the immunosuppressory properties of mesenchymal stem cells (MSCs) has recently attracted remarkable scientific interest. The aim of this work was to analyze the transport mechanisms of membrane and cytoplasmic components between T lymphocytes and adipose tissue-derived MSCs (AD-MSCs), by focusing on the role of distinct populations of EVs, direct cell-cell contacts, and the soluble mediators per se in modulating T lymphocyte function. We found that neither murine thymocytes and human primary T cells nor Jurkat lymphoblastoid cells incorporated appreciable amounts of MSC-derived microvesicles (MVs) or exosomes (EXOs). Moreover, these particles had no effect on the proliferation and IFN-γ production of in vitro-stimulated primary T cells. In contrast, AD-MSCs incorporated large amounts of membrane components from T cells as an intensive uptake of EXOs and MVs could be observed. Interestingly, we found a bidirectional exchange of cytoplasmic components between human AD-MSCs and primary T lymphocytes, mediated by tunneling nanotubes (TNTs) derived exclusively from the T cells. In contrast, TNTs couldn't be observed between AD-MSCs and the Jurkat cells. Our results reveal a novel and efficient way of intercellular communication between MSCs and T cells, and may help a better understanding of the immunomodulatory function of MSCs.

Background Folliculotropic mycosis fungoides (FMF) represents a variant of MF characterized by hair follicle invasion of mature, CD4-positive small lymphoid cells with cerebriform nuclei. The disease displays resistance to standard treatment modalities and has an unfavourable course. Objective Clinical analysis of 17 patients with FMF collected between 2005 and 2012, investigation of tumour cells and involved hair follicle. Methods Re-evaluation of clinical data, wide panel immunohistochemistry investigation on paraffin-embedded biopsy material, T-cell receptor gene rearrangement analysis of the samples. Results Male and older age group predominance, frequent head-neck involvement, acneiform lesions, keratotic plugs, cysts, nodules, follicular papules, alopecia and classic mycosis fungoides-like plaques represented the main clinical characteristics. Treatment response showed a wide range from transient complete response to therapy resistance and death due to the disease. The pathological alterations: folliculotropism, mild epidermotropism, follicular plugging, mucinous degeneration of hair follicle, basaloid hyperplasia, syringotropism were similar to those observed previously. The first case of a CD8-positive folliculotropic mycosis fungoides - with unusual clinical presentation - is reported here. Nestin overexpression of mesenchymal cells of the isthmic and suprabulbar regions of hair follicle and the reappearance of dermal nestin-expressing cells were observed in association with immature dendritic cell hyperplasia. Altered CK19 expression was detected suggesting a potential role of follicular keratinocytes in the disease process. It was found that a proportion of neoplastic T cells constantly express programmed death-1 receptor in our patients contrary to classic mycosis fungoides. Conclusion The spectrum of the clinical manifestation and the course of folliculotropic mycosis fungoides are broad and differ from classic mycosis fungoides. Folliculotropic neoplastic T-cell proliferation is associated with activation of inflammatory reactive T- and B-lymphoid cells, mesenchymal cells and changes in the hair follicle. [ABSTRACT FROM AUTHOR]