Tumour-infiltrating Gr-1+ myeloid cells antagonize senescence in cancer.

Aberrant activation of oncogenes or loss of tumour suppressor genes opposes malignant transformation by triggering a stable arrest in cell growth, which is termed cellular senescence. This process is finely tuned by both cell-autonomous and non-cell-autonomous mechanisms that regulate the entry of tumour cells to senescence. Whether tumour-infiltrating immune cells can oppose senescence is unknown. Here we show that at the onset of senescence, PTEN null prostate tumours in mice are massively infiltrated by a population of CD11b(+)Gr-1(+) myeloid cells that protect a fraction of proliferating tumour cells from senescence, thus sustaining tumour growth. Mechanistically, we found that Gr-1(+) cells antagonize senescence in a paracrine manner by interfering with the senescence-associated secretory phenotype of the tumour through the secretion of interleukin-1 receptor antagonist (IL-1RA). Strikingly, Pten-loss-induced cellular senescence was enhanced in vivo when Il1ra knockout myeloid cells were adoptively transferred to PTEN null mice. Therapeutically, docetaxel-induced senescence and efficacy were higher in PTEN null tumours when the percentage of tumour-infiltrating CD11b(+)Gr-1(+) myeloid cells was reduced using an antagonist of CXC chemokine receptor 2 (CXCR2). Taken together, our findings identify a novel non-cell-autonomous network, established by innate immunity, that controls senescence evasion and chemoresistance. Targeting this network provides novel opportunities for cancer therapy

An endogenous tumour-promoting ligand of the human aryl hydrocarbon receptor

Activation of the aryl hydrocarbon receptor (AHR) by environmental xenobiotic toxic chemicals, for instance 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin), has been implicated in a variety of cellular processes such as embryogenesis, transformation, tumorigenesis and inflammation. But the identity of an endogenous ligand activating the AHR under physiological conditions in the absence of environmental toxic chemicals is still unknown. Here we identify the tryptophan (Trp) catabolite kynurenine (Kyn) as an endogenous ligand of the human AHR that is constitutively generated by human tumour cells via tryptophan-2,3-dioxygenase (TDO), a liver- and neuron-derived Trp-degrading enzyme not yet implicated in cancer biology. TDO-derived Kyn suppresses antitumour immune responses and promotes tumour-cell survival and motility through the AHR in an autocrine/paracrine fashion. The TDO-AHR pathway is active in human brain tumours and is associated with malignant progression and poor survival. Because Kyn is produced during cancer progression and inflammation in the local microenvironment in amounts sufficient for activating the human AHR, these results provide evidence for a previously unidentified pathophysiological function of the AHR with profound implications for cancer and immune biology

The mutational landscape of lethal castration-resistant prostate cancer

none27noneGrasso, Catherine S.; Wu, Yi-Mi; Robinson, Dan R.; Cao, Xuhong; Dhanasekaran, Saravana M.; Khan, Amjad P.; Quist, Michael J.; Jing, Xiaojun; Lonigro, Robert J.; Brenner, J. Chad; Asangani, Irfan A.; Ateeq, Bushra; Chun, Sang Y.; Siddiqui, Javed; Sam, Lee; Anstett, Matt; Mehra, Rohit; Prensner, John R.; Palanisamy, Nallasivam; Ryslik, Gregory A.; Vandin, Fabio; Raphael, Benjamin J.; Kunju, Lakshmi P.; Rhodes, Daniel R.; Pienta, Kenneth J.; Chinnaiyan, Arul M.; Tomlins, Scott A.Grasso, Catherine S.; Wu, Yi Mi; Robinson, Dan R.; Cao, Xuhong; Dhanasekaran, Saravana M.; Khan, Amjad P.; Quist, Michael J.; Jing, Xiaojun; Lonigro, Robert J.; Brenner, J. Chad; Asangani, Irfan A.; Ateeq, Bushra; Chun, Sang Y.; Siddiqui, Javed; Sam, Lee; Anstett, Matt; Mehra, Rohit; Prensner, John R.; Palanisamy, Nallasivam; Ryslik, Gregory A.; Vandin, Fabio; Raphael, Benjamin J.; Kunju, Lakshmi P.; Rhodes, Daniel R.; Pienta, Kenneth J.; Chinnaiyan, Arul M.; Tomlins, Scott A