Deletion of MyD88 in T Cells Improves Antitumor Activity in Melanoma.

Cytotoxic CD8 T cells are central to the antitumor immune response by releasing cytotoxic granules that kill tumor cells. They are activated by antigen-presenting cells, which become activated by DAMPs (damage associated molecular patterns) through MyD88. However, the suppressive tumor microenvironment promotes T-cell tolerance to tumor antigens, in part by enhancing the activity of immune checkpoint molecules that prevent CD8 T-cell activation and cytotoxicity.

AKT2 Loss Impairs BRAF-Mutant Melanoma Metastasis.

Despite recent advances in treatment, melanoma remains the deadliest form of skin cancer due to its highly metastatic nature. Melanomas harboring oncogenic BRAF mutations combined with PTEN loss exhibit unrestrained PI3K/AKT signaling and increased invasiveness. However, the contribution of different AKT isoforms to melanoma initiation, progression, and metastasis has not been comprehensively explored, and questions remain about whether individual isoforms play distinct or redundant roles in each step.

AKT2 Loss Impairs BRAF-Mutant Melanoma Metastasis.

Despite recent advances in treatment, melanoma remains the deadliest form of skin cancer, due to its highly metastatic nature. Melanomas harboring oncogenic BRAF mutations combined with PTEN loss exhibit unrestrained PI3K/AKT signaling and increased invasiveness. However, the contribution of different AKT isoforms to melanoma initiation, progression, and metastasis has not been comprehensively explored, and questions remain whether individual isoforms play distinct or redundant roles in each step.

A kinase-independent function of cyclin-dependent kinase 6 promotes outer radial glia expansion and neocortical folding.

The neocortex, the center for higher brain function, first emerged in mammals and has become massively expanded and folded in humans, constituting almost half the volume of the human brain. Primary microcephaly, a developmental disorder in which the brain is smaller than normal at birth, results mainly from there being fewer neurons in the neocortex because of defects in neural progenitor cells (NPCs). Outer radial glia (oRGs), NPCs that are abundant in gyrencephalic species but rare in lissencephalic species, are thought to play key roles in the expansion and folding of the neocortex.

AKT1 Is Required for a Complete Palbociclib-Induced Senescence Phenotype in BRAF-V600E-Driven Human Melanoma.

Cellular senescence is a carefully regulated process of proliferative arrest accompanied by functional and morphologic changes. Senescence allows damaged cells to avoid neoplastic proliferation; however, the induction of the senescence-associated secretory phenotype (SASP) can promote tumor growth. The complexity of senescence may limit the efficacy of anti-neoplastic agents, such as CDK4/6 inhibitors (Cdk4/6i), that induce a senescence-like state in tumor cells.

Hyperlipidemia-induced metabolic changes in regulatory T cells result in altered function.

Regulatory T cells (Tregs) play a critical role in maintaining self-tolerance and controlling inflammation. However, physiologically relevant conditions that alter Treg function and drive disease pathogenesis are poorly understood and few have been defined. We have previously shown that induction of hyperlipidemia in mice results in changes in Tregs that reduce their function.

Akt3 induces oxidative stress and DNA damage by activating the NADPH oxidase via phosphorylation of p47.

Akt activation up-regulates the intracellular levels of reactive oxygen species (ROS) by inhibiting ROS scavenging. Of the Akt isoforms, Akt3 has also been shown to up-regulate ROS by promoting mitochondrial biogenesis. Here, we employ a set of isogenic cell lines that express different Akt isoforms, to show that the most robust inducer of ROS is Akt3.

Knockdown of CD44 expression decreases valve interstitial cell calcification in vitro.

The lack of pharmaceutical targets available to treat patients with calcific aortic valve disease (CAVD) necessitates further research into the specific mechanisms of the disease. The significant changes that occur to the aortic valves extracellular matrix (ECM) during the progression of CAVD suggests that these proteins may play an important role in calcification. Exploring the relationship between valve interstitial cells (VICs) and the ECM may lead to a better understand of CAVD mechanisms and potential pharmaceutical targets.

Proliferation of hippocampal progenitors relies on p27-dependent regulation of Cdk6 kinase activity.

Neural stem cells give rise to granule dentate neurons throughout life in the hippocampus. Upon activation, these stem cells generate fast proliferating progenitors that complete several rounds of divisions before differentiating into neurons. Although the mechanisms regulating the activation of stem cells have been intensively studied, little attention has been given so far to the intrinsic machinery allowing the expansion of the progenitor pool.

Non-destructive two-photon excited fluorescence imaging identifies early nodules in calcific aortic-valve disease.

Calcifications occur during the development of healthy bone, and at the onset of calcific aortic-valve disease (CAVD) and many other pathologies. Although the mechanisms regulating early calcium deposition are not fully understood, they may provide targets for new treatments and for early interventions. Here, we show that two-photon excited fluorescence (TPEF) can provide quantitative and sensitive readouts of calcific nodule formation, in particular in the context of CAVD.

Conditional deletion of RB1 in the Tie2 lineage leads to aortic valve regurgitation.

Objective: Aortic valve disease is a complex process characterized by valve interstitial cell activation, disruption of the extracellular matrix culminating in valve mineralization occurring over many years. We explored the function of the retinoblastoma protein (pRb) in aortic valve disease, given its critical role in mesenchymal cell differentiation including bone development and mineralization.

Approach And Results: We generated a mouse model of conditional pRb knockout (cKO) in the aortic valve regulated by Tie2-Cre-mediated excision of floxed RB1 alleles.

Cell-Cycle Proteins Control Production of Neutrophil Extracellular Traps.

Neutrophils are essential for immune defense and can respond to infection by releasing chromatin in the form of neutrophil extracellular traps (NETs). Here we show that NETs are induced by mitogens and accompanied by induction of cell-cycle markers, including phosphorylation of the retinoblastoma protein and lamins, nuclear envelope breakdown, and duplication of centrosomes. We identify cyclin-dependent kinases 4 and 6 (CDK4/6) as essential regulators of NETs and show that the response is inhibited by the cell-cycle inhibitor p21.

Cdk6 contributes to cytoskeletal stability in erythroid cells.

Mice lacking Cdk6 kinase activity suffer from mild anemia accompanied by elevated numbers of Ter119 cells in the bone marrow. The animals show hardly any alterations in erythroid development, indicating that Cdk6 is not required for proliferation and maturation of erythroid cells. There is also no difference in stress erythropoiesis following hemolysis However, erythrocytes have a shortened lifespan and are more sensitive to mechanical stress , suggesting differences in cytoskeletal architecture.

Osteosarcoma: prognosis plateau warrants retinoblastoma pathway targeted therapy.

Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents, affecting ~560 young patients in the United States annually. The term OS describes a diverse array of subtypes with varying prognoses, but the majority of tumors are high grade and aggressive. Perhaps because the true etiology of these aggressive tumors remains unknown, advances in OS treatment have reached a discouraging plateau, with only incremental improvements over the past 40 years.

Haploinsufficiency for BRCA1 leads to cell-type-specific genomic instability and premature senescence.

Although BRCA1 function is essential for maintaining genomic integrity in all cell types, it is unclear why increased risk of cancer in individuals harbouring deleterious mutations in BRCA1 is restricted to only a select few tissues. Here we show that human mammary epithelial cells (HMECs) from BRCA1-mutation carriers (BRCA1(mut/+)) exhibit increased genomic instability and rapid telomere erosion in the absence of tumour-suppressor loss. Furthermore, we uncover a novel form of haploinsufficiency-induced senescence (HIS) specific to epithelial cells, which is triggered by pRb pathway activation rather than p53 induction.

ClipR-59 interacts with Elmo2 and modulates myoblast fusion.

Recent studies using ClipR-59 knock-out mice implicated this protein in the regulation of muscle function. In this report, we have examined the role of ClipR-59 in muscle differentiation and found that ClipR-59 knockdown in C2C12 cells suppressed myoblast fusion. To elucidate the molecular mechanism whereby ClipR-59 regulates myoblast fusion, we carried out a yeast two-hybrid screen using ClipR-59 as the bait and identified Elmo2, a member of the Engulfment and cell motility protein family, as a novel ClipR-59-associated protein.

A little pRB can lead to big problems.

Germline deletion of RB1, the gene encoding the retinoblastoma tumor-suppressor protein pRB, predisposes to eye tumor formation upon loss of the remaining wild-type allele. Many functions affecting cell-cycle control, cell-cycle exit, and numerous other processes involved in the transformed phenotype have been ascribed to pRB, and deregulation of these processes is generally thought to result from complete loss of pRB in both hereditary and sporadic tumors in multiple tissues. Loss of just one allele of RB1 is now shown to lead to replication stress and aneuploidy in both mouse and human cells, and the mechanism through which this haploinsufficient phenotype is achieved may open up new opportunities for interceding both in tumor initiation and in treatment of extant tumors.

NDY1/KDM2B functions as a master regulator of polycomb complexes and controls self-renewal of breast cancer stem cells.

The JmjC domain histone H3K36me2/me1 demethylase NDY1/KDM2B is overexpressed in various types of cancer. Here we show that knocking down NDY1 in a set of 10 cell lines derived from a broad range of human tumors inhibited their anchorage-dependent and anchorage-independent growth by inducing senescence and/or apoptosis in some and by inhibiting G1 progression in all. We further show that the knockdown of NDY1 in mammary adenocarcinoma cell lines decreased the number, size, and replating efficiency of mammospheres and downregulated the stem cell markers ALDH and CD44, while upregulating CD24.

Transcription of angiogenin and ribonuclease 4 is regulated by RNA polymerase III elements and a CCCTC binding factor (CTCF)-dependent intragenic chromatin loop.

Angiogenin (ANG) and ribonuclease 4 (RNASE4), two members of the secreted and vertebrate-specific ribonuclease superfamily, play important roles in cancers and neurodegenerative diseases. The ANG and RNASE4 genes share genetic regions with promoter activities, but the structure and regulation of these putative promotes are unknown. We have characterized the promoter regions, defined the transcription start site, and identified a mechanism of transcription regulation that involves both RNA polymerase III (Pol III) elements and CCCTC binding factor (CTCF) sites.

Immune response to RB1-regulated senescence limits radiation-induced osteosarcoma formation.

Ionizing radiation (IR) and germline mutations in the retinoblastoma tumor suppressor gene (RB1) are the strongest risk factors for developing osteosarcoma. Recapitulating the human predisposition, we found that Rb1+/- mice exhibited accelerated development of IR-induced osteosarcoma, with a latency of 39 weeks. Initial exposure of osteoblasts to carcinogenic doses of IR in vitro and in vivo induced RB1-dependent senescence and the expression of a panel of proteins known as senescence-associated secretory phenotype (SASP), dominated by IL-6.

CDK6 binds and promotes the degradation of the EYA2 protein.

Cyclin-dependent kinase 6 (Cdk6) is a D-Cyclin-activated kinase that is directly involved in driving the cell cycle through inactivation of pRB in G₁ phase. Increasingly, evidence suggests that CDK6, while directly driving the cell cycle, may only be essential for proliferation of specialized cell types, agreeing with the notion that CDK6 also plays an important role in differentiation. Here, evidence is presented that CDK6 binds to and promotes degradation of the EYA2 protein.