Proteomic Profiling of Lymph Nodes Differentiates Classic Hodgkin Lymphoma With and Without Skeletal Involvement.

Classic Hodgkin lymphoma (CHL) is a highly curable disease, even in advanced stages. Controversy remains over whether bone involvement negatively affects overall and progression-free survival in patients treated with intensive chemotherapy regimens. Whether cases that present with bone lesions harbor specific tumor microenvironmental features is unknown. We investigated protein expression in diagnostic lymph node biopsies from CHL patients with and without skeletal involvement at diagnosis to identify potential markers of skeletal disease. Protein expression patterns in diagnostic formalin-fixed paraffin-embedded lymphoma lymph node samples from CHL patients were analyzed by nano-liquid chromatography-tandem mass spectrometry. Patients were grouped according to skeletal involvement, which was defined as the presence of one or more FDG-avid lesions on a diagnostic FDG-PET/CT scan. Protein profiles identified patients with skeletal disease at diagnosis and showed disrupted cellular pathways, including immune system processes, cell adhesion, and cell growth/survival. Immunohistochemical evaluation also demonstrated differential expressions of angiotensin-converting enzyme (ACE), intercellular adhesion molecule 3 (ICAM3), integrin alpha-X (ITGAX), and calreticulin (CALR). In conclusion, proteomics identified altered protein expression profiles in lymph nodes among CHL cases presenting with disease disseminated to the skeletal system, which implies altered disease pathogenesis for these patients.

Proteomics identifies apoptotic markers as predictors of histological transformation in patients with follicular lymphoma.

Follicular lymphoma (FL) is an indolent lymphoma with a generally favorable prognosis. However, histological transformation (HT) to a more aggressive disease leads to markedly inferior outcomes. This study aims to identify biological differences predictive of HT at the time of initial FL diagnosis. We show differential protein expression between diagnostic lymphoma samples from patients with subsequent HT (subsequently-transforming FL [st-FL]; n = 20) and patients without HT (nontransforming FL [nt-FL]; n = 34) by label-free quantification nano liquid chromatography-tandem mass spectrometry analysis. Protein profiles identified patients with high risk of HT. This was accompanied by disturbances in cellular pathways influencing apoptosis, the cytoskeleton, cell cycle, and immune processes. Comparisons between diagnostic st-FL samples and paired transformed FL (n = 20) samples demonstrated differential protein profiles and disrupted cellular pathways, indicating striking biological differences from the time of diagnosis up to HT. Immunohistochemical analysis of apoptotic proteins, CASP3, MCL1, BAX, BCL-xL, and BCL-rambo, confirmed higher expression levels in st-FL than in nt-FL samples (P < .001, P = .015, P = .003, P = .025, and P = .057, respectively). Moreover, all 5 markers were associated with shorter transformation-free survival (TFS; P < .001, P = .002, P < .001, P = .069, and P = .010, respectively). Notably, combining the expression of these proteins in a risk score revealed increasingly inferior TFS with an increasing number of positive markers. In conclusion, proteomics identified altered protein expression profiles (particularly apoptotic proteins) at the time of FL diagnosis, which predicted later transformation.

Cardiac glycosides are broad-spectrum senolytics.

Senescence is a cellular stress response that results in the stable arrest of old, damaged or preneoplastic cells. Oncogene-induced senescence is tumor suppressive but can also exacerbate tumorigenesis through the secretion of pro-inflammatory factors from senescent cells. Drugs that selectively kill senescent cells, termed senolytics, have proved beneficial in animal models of many age-associated diseases. Here, we show that the cardiac glycoside, ouabain, is a senolytic agent with broad activity. Senescent cells are sensitized to ouabain-induced apoptosis, a process mediated in part by induction of the pro-apoptotic Bcl2-family protein NOXA. We show that cardiac glycosides synergize with anti-cancer drugs to kill tumor cells and eliminate senescent cells that accumulate after irradiation or in old mice. Ouabain also eliminates senescent preneoplastic cells. Our findings suggest that cardiac glycosides may be effective anti-cancer drugs by acting through multiple mechanism. Given the broad range of senescent cells targeted by cardiac glycosides their use against age-related diseases warrants further exploration.

Innate immune sensing of cytosolic chromatin fragments through cGAS promotes senescence.

Cellular senescence is triggered by various distinct stresses and characterized by a permanent cell cycle arrest. Senescent cells secrete a variety of inflammatory factors, collectively referred to as the senescence-associated secretory phenotype (SASP). The mechanism(s) underlying the regulation of the SASP remains incompletely understood. Here we define a role for innate DNA sensing in the regulation of senescence and the SASP. We find that cyclic GMP-AMP synthase (cGAS) recognizes cytosolic chromatin fragments in senescent cells. The activation of cGAS, in turn, triggers the production of SASP factors via stimulator of interferon genes (STING), thereby promoting paracrine senescence. We demonstrate that diverse stimuli of cellular senescence engage the cGAS-STING pathway in vitro and we show cGAS-dependent regulation of senescence following irradiation and oncogene activation in vivo. Our findings provide insights into the mechanisms underlying cellular senescence by establishing the cGAS-STING pathway as a crucial regulator of senescence and the SASP.

Distinct Functions of Senescence-Associated Immune Responses in Liver Tumor Surveillance and Tumor Progression.

Oncogene-induced senescence causes hepatocytes to secrete cytokines, which induce their immune-mediated clearance to prevent tumor initiation, a process termed "senescence surveillance." However, senescent hepatocytes give rise to hepatocellular carcinomas (HCCs), if the senescence program is bypassed or if senescent cells are not cleared. Here, we show context-specific roles for CCR2+ myeloid cells in liver cancer. Senescence surveillance requires the recruitment and maturation of CCR2+ myeloid cells, and CCR2 ablation caused outgrowth of HCC. In contrast, HCC cells block the maturation of recruited myeloid precursors, which, through NK cell inhibition, promote growth of murine HCC and worsen the prognosis and survival of human HCC patients. Thus, while senescent hepatocyte-secreted chemokines suppress liver cancer initiation, they may accelerate the growth of fully established HCC.

mTOR regulates MAPKAPK2 translation to control the senescence-associated secretory phenotype.

Senescent cells secrete a combination of factors collectively known as the senescence-associated secretory phenotype (SASP). The SASP reinforces senescence and activates an immune surveillance response, but it can also show pro-tumorigenic properties and contribute to age-related pathologies. In a drug screen to find new SASP regulators, we uncovered the mTOR inhibitor rapamycin as a potent SASP suppressor. Here we report a mechanism by which mTOR controls the SASP by differentially regulating the translation of the MK2 (also known as MAPKAPK2) kinase through 4EBP1. In turn, MAPKAPK2 phosphorylates the RNA-binding protein ZFP36L1 during senescence, inhibiting its ability to degrade the transcripts of numerous SASP components. Consequently, mTOR inhibition or constitutive activation of ZFP36L1 impairs the non-cell-autonomous effects of senescent cells in both tumour-suppressive and tumour-promoting contexts. Altogether, our results place regulation of the SASP as a key mechanism by which mTOR could influence cancer, age-related diseases and immune responses.