Metastasis suppressor function of tumor necrosis factor-related apoptosis-inducing ligand-R in mice: implications for TRAIL-based therapy in humans?

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising candidate for cancer therapy, as it can induce apoptosis specifically in tumor cells but not in normal cells. Although earlier mouse tumor studies revealed a strong tissue dependency of TRAIL and its death receptor in suppressing primary tumorigenesis or experimental metastases, we recently found that TRAIL-R inhibits lymph node metastases without affecting primary tumor formation in a mouse model of multistage skin tumorigenesis. This finding uncouples the role of TRAIL in primary tumorigenesis from metastasis formation, likely by sensitization of previously TRAIL-resistant tumor cells upon detachment, an early step required for metastasis formation. Therefore, TRAIL-R is a novel metastasis suppressor, suggesting that TRAIL-related tumor therapy might be most effective in primary tumors and early metastatic cancers, before selection for TRAIL resistance occurs

Loss of inter-cellular cooperation by complete epithelial-mesenchymal transition supports favorable outcomes in basal breast cancer patients.

According to the sequential metastasis model, aggressive mesenchymal (M) metastasis-initiating cells (MICs) are generated by an epithelial-mesenchymal transition (EMT) which eventually is reversed by a mesenchymal-epithelial transition (MET) and outgrowth of life-threatening epithelial (E) macrometastases. Paradoxically, in breast cancer M signatures are linked with more favorable outcomes than E signatures, and M cells are often dispensable for metastasis in mouse models. Here we present evidence at the cellular and patient level for the cooperation metastasis model, according to which E cells are MICs, while M cells merely support E cell persistence through cooperation. We tracked the fates of co-cultured E and M clones and of fluorescent CDH1-promoter-driven cell lines reporting the E state derived from basal breast cancer HMLER cells. Cells were placed in suspension state and allowed to reattach and select an EMT cell fate. Flow cytometry, single cell and bulk gene expression analyses revealed that only pre-existing E cells generated E cells, mixed E/M populations, or stem-like hybrid E/M cells after suspension and that complete EMT manifest in M clones and CDH1-negative reporter cells resulted in loss of cell plasticity, suggesting full transdifferentiation. Mechanistically, E-M coculture experiments supported the persistence of pre-existing E cells where M cells inhibited EMT of E cells in a mutual cooperation via direct cell-cell contact. Consistently, M signatures were associated with more favorable patient outcomes compared to E signatures in breast cancer, specifically in basal breast cancer patients. These findings suggest a potential benefit of complete EMT for basal breast cancer patients

The Glanville fritillary genome retains ancient karyotype and reveals selective chromosomal fusions in Lepidoptera

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Caspase-10 is recruited to and activated at the native TRAIL and CD95 death-inducing signalling complexes in a FADD-dependent manner but can not functionally substitute caspase-8

The involvement of the death adaptor protein FADD and the apoptosis-initiating caspase-8 in CD95 and TRAIL death signalling has recently been demonstrated by the analysis of the native death-inducing signalling complex (DISC) that forms upon ligand-induced receptor cross-linking. However, the role of caspase-10, the other death-effector-domain-containing caspase besides caspase-8, in death receptor signalling has been controversial. Here we show that caspase-10 is recruited not only to the native TRAIL DISC but also to the native CD95 DISC, and that FADD is necessary for its recruitment to and activation at these two protein complexes. With respect to the function of caspase-10, we show that it is not required for apoptosis induction. In addition, caspase-10 can not substitute for caspase-8, as the defect in apoptosis induction observed in caspase-8-deficient cells could not be rescued by overexpression of caspase-10. Finally, we demonstrate that caspase-10 is cleaved during CD95-induced apoptosis of activated T cells. These results show that caspase-10 activation occurs in primary cells, but that its function differs from that of caspase-8

Stemness of the hybrid Epithelial/Mesenchymal State in Breast Cancer and Its Association with Poor Survival.

Breast cancer stem cells (CSCs) are thought to drive recurrence and metastasis. Their identity has been linked to the epithelial to mesenchymal transition (EMT) but remains highly controversial since-depending on the cell-line studied-either epithelial (E) or mesenchymal (M) markers, alone or together have been associated with stemness. Using distinct transcript expression signatures characterizing the three different E, M and hybrid E/M cell-types, our data support a novel model that links a mixed EM signature with stemness in 1) individual cells, 2) luminal and basal cell lines, 3) in vivo xenograft mouse models, and 4) in all breast cancer subtypes. In particular, we found that co-expression of E and M signatures was associated with poorest outcome in luminal and basal breast cancer patients as well as with enrichment for stem-like cells in both E and M breast cell-lines. This link between a mixed EM expression signature and stemness was explained by two findings: first, mixed cultures of E and M cells showed increased cooperation in mammosphere formation (indicative of stemness) compared to the more differentiated E and M cell-types. Second, single-cell qPCR analysis revealed that E and M genes could be co-expressed in the same cell. These hybrid E/M cells were generated by both E or M cells and had a combination of several stem-like traits since they displayed increased plasticity, self-renewal, mammosphere formation, and produced ALDH1+ progenies, while more differentiated M cells showed less plasticity and E cells showed less self-renewal. Thus, the hybrid E/M state reflecting stemness and its promotion by E-M cooperation offers a dual biological rationale for the robust association of the mixed EM signature with poor prognosis, independent of cellular origin. Together, our model explains previous paradoxical findings that breast CSCs appear to be M in luminal cell-lines but E in basal breast cancer cell-lines. Our results suggest that targeting E/M heterogeneity by eliminating hybrid E/M cells and cooperation between E and M cell-types could improve breast cancer patient survival independent of breast cancer-subtype

The conventional versus a new integrative CSC model for breast cancer.

<p>(A) In luminal epithelial cell-lines (e.g. in HMLE, HMLER, MCF7) the conventional model describes breast CSCs as M cells and ‘non cancer stem cells’ as E cells. Paradoxically, in more basal mesenchymal cancer cell-lines (MDA-MB231 cells, MCF10ACA1, 4T1) the more E gene-expressing cells are associated with CSC-properties. Thus, the identity of CSCs appears to be context-dependent. (B) Our model for CSCs integrates and explains these paradoxes by the existence of stem-like intermediate hybrid E/M cells independent of the tumor cell line. We propose that compared to more ‘polarized’ differentiated E (capable of plasticity) and M cell-types (capable of self-renewal), undifferentiated hybrid E/M cells can generate more mammospheres and heterogeneous progeny due to their capacity of both, self-renewal and plasticity. Arrows indicate possible state transitions (incomplete EMT and MET) between the instable hybrid E/M state and the extreme stable E and M states. Stemness of the intermediate E/M state is reflected both by presence of stem-like hybrid E/M cells and by co-presence of E and M cell-types due to cooperation. Context-independency of the stemness of the intermediate E/M state explains the paradoxical context-dependent meaning of E genes in basal tumors and M cell lines and stemness of M genes in luminal B tumors and E cell-lines (A).</p

Co-culture of E and M cell-types synergistically increases mammosphere formation.

<p>(A) Representative light microscope images (10x objective) from mammospheres of 500 E5, 500 M5, and 500 E5 + 500 M5-derived mammospheres after two weeks suspension culture. (B) Total number of primary mammospheres derived from 500 (1x) or 1000 (2x) cells per cell-type seeded (from A) after two weeks suspension culture. (C) Total number of primary mammospheres grown from 500 (1x) freshly sorted CD24+/CD44-(E) cells, 500 CD24-/CD44+(M) cells, the co-culture, or 500 un-gated HP cells (‘all HP’) after two weeks of mammosphere formation. (D) Relative number of primary (seeded 2,000 cells per cell line per well) and secondary mammospheres from M4 grown with or without E5 cells or HP cells. After two weeks 10% of total number of dissociated cells from the indicated primary mammosphere samples were reseeded for secondary mammospheres and counted after one week. Mammospheres per well relative to that of M4-derived spheres are shown.</p