Impact of house dust mite in vitiligo skin: environmental contribution to increased cutaneous immunity and melanocyte detachment.

BACKGROUND: Vitiligo is an autoimmune skin disorder characterized by loss of melanocytes. Protease-mediated disruption of junctions between keratinocytes and/or keratinocyte intrinsic dysfunction may directly contribute to melanocyte loss. House dust mite (HDM), an environmental allergen with potent protease activity, contributes to respiratory and gut disease but also to atopic dermatitis and rosacea. OBJECTIVES: To verify if HDM can contribute to melanocyte detachment in vitiligo and if so, by which mechanism(s). METHODS: Using primary human keratinocytes, human skin biopsies from healthy donors and patients with vitiligo, and 3D reconstructed human epidermis, we studied the effect of HDM on cutaneous immunity, tight and adherent junction expression and melanocyte detachment. RESULTS: HDM increased keratinocyte production of vitiligo-associated cytokines and chemokines and increased expression of toll-like receptor (TLR)-4. This was associated with increased in situ matrix-metalloproteinase (MMP)-9 activity, reduced cutaneous expression of adherent protein E-cadherin, increased soluble E-cadherin in culture supernatant and significantly increased number of suprabasal melanocytes in the skin. This effect was dose-dependent and driven by cysteine protease Der p1 and MMP-9. Selective MMP-9 inhibitor, Ab142180, restored E-cadherin expression and inhibited HDM-induced melanocyte detachment. Keratinocytes from patients with vitiligo were more sensitive to HDM-induced changes than healthy keratinocytes. All results were confirmed in a 3D model of healthy skin and in human skin biopsies. CONCLUSIONS: Our results highlight that environmental mite may act as an external source of pathogen-associated molecular pattern molecules in vitiligo and topical MMP-9 inhibitors may be useful therapeutic targets. Whether HDM contributes to the onset of flares in vitiligo remains to be tested in carefully controlled trials.

Flow Cytometry-based Method for Efficient Sorting of Senescent Cells.

Cellular senescence is a reprogrammed cell state triggered as an adaptative response to a variety of stresses, most often those affecting the genome integrity. Senescent cells accumulate in most tissues with age and contribute to the development of several pathologies. Studying molecular pathways involved in senescence induction and maintenance, or in senescence escape, can be hindered by the heterogeneity of senescent cell populations. Here, we describe a flow cytometry strategy for sorting senescent cells according to three senescence canonical markers whose thresholds can be independently adapted to be more or less stringent: (i) the senescence-associated-ß-galactosidase (SA-ß-Gal) activity, detected using 5-dodecanoylaminofluorescein Di-ß-D-galactopyranoside (C12FDG), a fluorigenic substrate of ß-galactosidase; (ii) cell size, proportional to the forward scatter value, since increased size is one of the major changes observed in senescent cells; and (iii) cell granularity, proportional to the side scatter value, which reflects the accumulation of aggregates, lysosomes, and altered mitochondria in senescent cells. We applied this protocol to the sorting of normal human fibroblasts at the replicative senescence plateau. We highlighted the challenge of sorting these senescent cells because of their large sizes, and established that it requires using sorters equipped with a nozzle of an unusually large diameter: at least 200 µm. We present evidence of the sorting efficiency and sorted cell viability, as well as of the senescent nature of the sorted cells, confirmed by the detection of other senescence markers, including the expression of the CKI p21 and the presence of 53BP1 DNA damage foci. Our protocol makes it possible, for the first time, to sort senescent cells from contaminating proliferating cells and, at the same time, to sort subpopulations of senescent cells featuring senescent markers to different extents. Graphical abstract.

The out-of-field dose in radiation therapy induces delayed tumorigenesis by senescence evasion.

A rare but severe complication of curative-intent radiation therapy is the induction of second primary cancers. These cancers preferentially develop not inside the planning target volume (PTV) but around, over several centimeters, after a latency period of 1-40 years. We show here that normal human or mouse dermal fibroblasts submitted to the out-of-field dose scattering at the margin of a PTV receiving a mimicked patient's treatment do not die but enter in a long-lived senescent state resulting from the accumulation of unrepaired DNA single-strand breaks, in the almost absence of double-strand breaks. Importantly, a few of these senescent cells systematically and spontaneously escape from the cell cycle arrest after a while to generate daughter cells harboring mutations and invasive capacities. These findings highlight single-strand break-induced senescence as the mechanism of second primary cancer initiation, with clinically relevant spatiotemporal specificities. Senescence being pharmacologically targetable, they open the avenue for second primary cancer prevention.

Vitiligo Skin T Cells Are Prone to Produce Type 1 and Type 2 Cytokines to Induce Melanocyte Dysfunction and Epidermal Inflammatory Response Through Jak Signaling.

Vitiligo is a T cell-mediated inflammatory skin disorder characterized by the loss of epidermal melanocytes. However, the contribution of melanocytes to the physiopathology of the disease in response to the T-cell microenvironment remains unclear. Here, using NanoString technology and multiplex ELISA, we show that active vitiligo perilesional skin is characterized by prominent type 1 and 2 associated immune responses. The vitiligo skin T-cell secretome downregulated melanocyte function and adhesion while increasing melanocyte mitochondrial metabolism and expression of inflammatory cytokines and chemokines by epidermal cells. The Jak1/2 inhibitor ruxolitinib strongly inhibited such effects on epidermal cells. Our data highlight that vitiligo is more complex than previously thought, with prominent combined activities of both T helper type 1- and T helper type 2-related cytokines inducing inflammatory responses of epidermal cells. Melanocytes do not appear only to be a target of T cells in vitiligo but could actively contribute to perpetuate inflammation. Jak inhibitors could prevent the impact of T cells on epidermal cells and pigmentation, highlighting their potential clinical benefit in vitiligo.

Type-1 cytokines regulate MMP-9 production and E-cadherin disruption to promote melanocyte loss in vitiligo.

Loss of melanocytes is the pathological hallmark of vitiligo, a chronic inflammatory skin depigmenting disorder induced by exaggerated immune response, including autoreactive CD8 T cells producing high levels of type 1 cytokines. However, the interplay between this inflammatory response and melanocyte disappearance remains to be fully characterized. Here, we demonstrate that vitiligo skin contains a significant proportion of suprabasal melanocytes, associated with disruption of E-cadherin expression, a major protein involved in melanocyte adhesion. This phenomenon is also observed in lesional psoriatic skin. Importantly, apoptotic melanocytes were mainly observed once cells were detached from the basal layer of the epidermis, suggesting that additional mechanism(s) could be involved in melanocyte loss. The type 1 cytokines IFN-γ and TNF-α induce melanocyte detachment through E-cadherin disruption and the release of its soluble form, partly due to MMP-9. The levels of MMP-9 are increased in the skin and sera of patients with vitiligo, and MMP-9 is produced by keratinocytes in response to IFN-γ and TNF-α. Inhibition of MMP-9 or the JAK/STAT signaling pathway prevents melanocyte detachment in vitro and in vivo. Therefore, stabilization of melanocytes in the basal layer of the epidermis by preventing E-cadherin disruption appears promising for the prevention of depigmentation occurring in vitiligo and during chronic skin inflammation.

Pre-malignant transformation by senescence evasion is prevented by the PERK and ATF6alpha branches of the Unfolded Protein Response.

The incidence of carcinomas highly increases with age. However, the initial steps of the age-related molecular carcinogenic processes remain poorly characterized. We previously showed that normal human epidermal keratinocytes spontaneously and systematically escape from senescence to give rise to preneoplastic emerging cells through a process called post-senescence neoplastic emergence (PSNE). To identify molecular pathways involved in the switch from senescence to pre-transformation, we performed Connectivity Map analyses and DAVID functional annotations followed by hierarchical clustering and multidimensional scaling of the gene expression signature of PSNE cells. We identified endoplasmic reticulum stress related pathways as key regulators of PSNE. Invalidation by RNA interference of the UPR sensors PERK, ATF6α, but not IRE1α, delayed the occurrence of senescence when performed in pre-senescent cells, and increased the PSNE frequency when performed in already senescent cells. Conversely, endoplasmic reticulum stress inducers applied to already senescent cells decreased the frequency of PSNE. In conclusion, these results indicate that the activation of the UPR could protect from the early carcinogenic steps by senescence evasion. This opens new avenues to explore therapeutics that could be useful in decreasing the age-associated tumor incidence.

Chronic myeloid leukemia progenitor cells require autophagy when leaving hypoxia-induced quiescence.

Albeit tyrosine kinase inhibitors anti-Abl used in Chronic Myeloid Leukemia (CML) block the deregulated activity of the Bcr-Abl tyrosine kinase and induce remission in 90% of patients, they do not eradicate immature hematopoietic compartments of leukemic stem cells. To elucidate if autophagy is important for stem cell survival and/or proliferation, we used culture in low oxygen concentration (0.1% O2 for 7 days) followed back by non-restricted O2 supply (normoxic culture) to mimic stem cell proliferation and commitment. Knockdown of Atg7 expression, a key player in autophagy, in K562 cell line inhibited autophagy compared to control cells. Upon 7 days at 0.1% O2 both K562 and K562 shATG7 cells stopped to proliferate and a similar amount of viable cells remained. Back to non-restricted O2 supply K562 cells proliferate whereas K562 shATG7 cells exhibited strong apoptosis. Using immunomagnetic sorted normal and CML CD34+ cells, we inhibited the autophagic process by lentiviral infection expressing shATG7 or using a Vps34 inhibitor. Both, normal and CML CD34+ cells either competent or deficient for autophagy stopped to proliferate in hypoxia. Surprisingly, while normal CD34+ cells proliferate back to non restricted O2 supply, the CML CD34+ cells deficient for autophagy failed to proliferate. All together, these results suggest that autophagy is required for CML CD34+ commitment while it is dispensable for normal CD34 cells.

Fast spatial-selective delivery into live cells.

Intracellular delivery of functional compounds into living cells is of great importance for cell biology as well as therapeutic applications. Often it is sufficient that the compound of interest (being a molecule or nanoparticle) is delivered to the cell population as a whole. However, there are applications that would benefit considerably from the possibility of delivering a compound to a certain subpopulation of cells, or even in selected single cells. Here we report on an integrated platform for high-throughput spatially resolved nanoparticle-enhanced photoporation (SNAP) of adherent cells. SNAP enables safe, intracellular delivery of exogenously administered nanomaterials in selected subpopulations of cells, even down to the single cell level. We demonstrate the power of SNAP by selectively delivering a safe contrast agent into a subpopulation of polynucleated keratinocytes, enabling their downstream purification for unraveling their role in neoplasm formation. The flexibility and speed with which individual cells can be labeled make SNAP an ideal tool for high-throughput applications, not only for selective labeling but also for targeted drug delivery.

ATF6α regulates morphological changes associated with senescence in human fibroblasts.

Cellular senescence is known as an anti-tumor barrier and is characterized by a number of determinants including cell cycle arrest, senescence associated ß-galactosidase activity and secretion of pro-inflammatory mediators. Senescent cells are also subjected to enlargement, cytoskeleton-mediated shape changes and organelle alterations. However, the underlying molecular mechanisms responsible for these last changes remain still uncharacterized. Herein, we have identified the Unfolded Protein Response (UPR) as a player controlling some morphological aspects of the senescent phenotype. We show that senescent fibroblasts exhibit ER expansion and mild UPR activation, but conserve an ER stress adaptive capacity similar to that of exponentially growing cells. By genetically invalidating the three UPR sensors in senescent fibroblasts, we demonstrated that ATF6α signaling dictates senescence-associated cell shape modifications. We also show that ER expansion and increased secretion of the pro-inflammatory mediator IL6 were partly reversed by silencing ATF6α in senescent cells. Moreover, ATF6α drives the increase of senescence associated-ß-galactosidase activity. Collectively, these findings unveil a novel and central role for ATF6α in the establishment of morphological features of senescence in normal human primary fibroblasts.

Alpha-fetoprotein is a biomarker of unfolded protein response and altered proteostasis in hepatocellular carcinoma cells exposed to sorafenib.

Sorafenib is the treatment of reference for advanced hepatocellular carcinoma (HCC). A decrease in the serum levels of Alpha-fetoprotein (AFP) is reported to be the biological parameter that is best associated with disease control by sorafenib. In order to provide a biological rationale for the variations of AFP, we analyzed the various steps of AFP production in human HCC cell lines exposed to sorafenib. Sorafenib dramatically reduced the levels of AFP produced by HCC cells independently of its effect on cell viability. The mRNA levels of AFP decreased upon sorafenib treatment, while the AFP protein remained localized in the Golgi apparatus. Sorafenib activated the Regulated Inositol-Requiring Enzyme-1α (IRE-1α) and the PKR-like ER Kinase (PERK)-dependent arms of the Unfolded Protein Response (UPR). The inhibition of IRE-1α partially restored the mRNA levels of AFP upon treatment with sorafenib. The inhibition of both pathways partially prevented the drop in the production of AFP induced by sorafenib. The findings provide new insights on the regulation of AFP, and identify it as a biomarker suitable for the exploration of HCC cell proteostasis in the context of therapeutic targeting.

A novel somatic mutation in ACD induces telomere lengthening and apoptosis resistance in leukemia cells.

BACKGROUND: The identification of oncogenic driver mutations has largely relied on the assumption that genes that exhibit more mutations than expected by chance are more likely to play an active role in tumorigenesis. Major cancer sequencing initiatives have therefore focused on recurrent mutations that are more likely to be drivers. However, in specific genetic contexts, low frequency mutations may also be capable of participating in oncogenic processes. Reliable strategies for identifying these rare or even patient-specific (private) mutations are needed in order to elucidate more personalized approaches to cancer diagnosis and treatment. METHODS: Here we performed whole-exome sequencing on three cases of childhood pre-B acute lymphoblastic leukemia (cALL), representing three cytogenetically-defined subgroups (high hyperdiploid, t(12;21) translocation, and cytogenetically normal). We applied a data reduction strategy to identify both common and rare/private somatic events with high functional potential. Top-ranked candidate mutations were subsequently validated at high sequencing depth on an independent platform and in vitro expression assays were performed to evaluate the impact of identified mutations on cell growth and survival. RESULTS: We identified 6 putatively damaging non-synonymous somatic mutations among the three cALL patients. Three of these mutations were well-characterized common cALL mutations involved in constitutive activation of the mitogen-activated protein kinase pathway (FLT3 p.D835Y, NRAS p.G13D, BRAF p.G466A). The remaining three patient-specific mutations (ACD p.G223V, DOT1L p.V114F, HCFC1 p.Y103H) were novel mutations previously undescribed in public cancer databases. Cytotoxicity assays demonstrated a protective effect of the ACD p.G223V mutation against apoptosis in leukemia cells. ACD plays a key role in protecting telomeres and recruiting telomerase. Using a telomere restriction fragment assay, we also showed that this novel mutation in ACD leads to increased telomere length in leukemia cells. CONCLUSION: This study identified ACD as a novel gene involved in cALL and points to a functional role for ACD in enhancing leukemia cell survival. These results highlight the importance of rare/private somatic mutations in understanding cALL etiology, even within well-characterized molecular subgroups.

Mycophenolic Acid overcomes imatinib and nilotinib resistance of chronic myeloid leukemia cells by apoptosis or a senescent-like cell cycle arrest.

We used K562 cells sensitive or generated resistant to imatinib or nilotinib to investigate their response to mycophenolic acid (MPA). MPA induced DNA damage leading to cell death with a minor contribution of apoptosis, as revealed by annexin V labeling (up to 25%). In contrast, cell cycle arrest and positive staining for senescence-associated ß-galactosidase activity were detected for a large cell population (80%). MPA-induced cell death was potentialized by the inhibition of autophagy and this is associated to the upregulation of apoptosis. In contrast, senescence was neither decreased nor abrogated in autophagy deficient K562 cells. Primary CD34 cells from CML patients sensitive or resistant to imatinib or nilotinib respond to MPA although apoptosis is mainly detected. These results show that MPA is an interesting tool to overcome resistance in vitro and in vivo mainly in the evolved phase of the disease.

Quantitative phosphoproteomics revealed interplay between Syk and Lyn in the resistance to nilotinib in chronic myeloid leukemia cells.

In this study, we have addressed how Lyn kinase signaling mediates nilotinib-resistance by quantitative phospho-proteomics using Stable Isotope Labeling with Amino acid in Cell culture. We have found an increased tyrosine phosphorylation of 2 additional tyrosine kinases in nilotinib-resistant cells: the spleen tyrosine kinase Syk and the UFO family receptor tyrosine kinase Axl. This increased tyrosine phosphorylation involved an interaction of these tyrosine kinases with Lyn. Inhibition of Syk by the inhibitors R406 or BAY 61-3606 or by RNA interference restored the capacity of nilotinib to inhibit cell proliferation. Conversely, coexpression of Lyn and Syk were required to fully induce resistance to nilotinib in drug-sensitive cells. Surprisingly, the knockdown of Syk also strongly decreased tyrosine phosphorylation of Lyn and Axl, thus uncovering interplay between Syk and Lyn. We have shown the involvement of the adaptor protein CDCP-1 in resistance to nilotinib. Interestingly, the expression of Axl and CDCP1 were found increased both in a nilotinib-resistant cell line and in nilotinib-resistant CML patients. We conclude that an oncogenic signaling mediated by Lyn and Syk can bypass the need of Bcr-Abl in CML cells. Thus, targeting these kinases may be of therapeutic value to override imatinib or nilotinib resistance in CML.