Dysregulated naive B cells and de novo autoreactivity in severe COVID-19.

Severe SARS-CoV-2 infection1 has been associated with highly inflammatory immune activation since the earliest days of the COVID-19 pandemic2-5. More recently, these responses have been associated with the emergence of self-reactive antibodies with pathologic potential6-10, although their origins and resolution have remained unclear11. Previously, we and others have identified extrafollicular B cell activation, a pathway associated with the formation of new autoreactive antibodies in chronic autoimmunity12,13, as a dominant feature of severe and critical COVID-19 (refs. 14-18). Here, using single-cell B cell repertoire analysis of patients with mild and severe disease, we identify the expansion of a naive-derived, low-mutation IgG1 population of antibody-secreting cells (ASCs) reflecting features of low selective pressure. These features correlate with progressive, broad, clinically relevant autoreactivity, particularly directed against nuclear antigens and carbamylated proteins, emerging 10-15 days after the onset of symptoms. Detailed analysis of the low-selection compartment shows a high frequency of clonotypes specific for both SARS-CoV-2 and autoantigens, including pathogenic autoantibodies against the glomerular basement membrane. We further identify the contraction of this pathway on recovery, re-establishment of tolerance standards and concomitant loss of acute-derived ASCs irrespective of antigen specificity. However, serological autoreactivity persists in a subset of patients with postacute sequelae, raising important questions as to the contribution of emerging autoreactivity to continuing symptomology on recovery. In summary, this study demonstrates the origins, breadth and resolution of autoreactivity in severe COVID-19, with implications for early intervention and the treatment of patients with post-COVID sequelae.

Myeloablative busulfan/cytoxan conditioning versus reduced-intensity fludarabine/melphalan conditioning for allogeneic hematopoietic stem cell transplant in patients with acute myelogenous leukemia.

Fludarabine and melphalan (Flu/Mel) has emerged as a more tolerable chemotherapy-based conditioning regimen compared with busulfan and cyclophosphamide (Bu/Cy) for allogeneic stem cell transplant (allo-hematopoietic stem cell transplantation (HSCT)) patients with acute myelogenous leukemia (AML). We conducted a retrospective review of a single-institution database including patients with AML who received allo-HSCT following conditioning with Mel/Flu or Bu/Cy-based regimens. We performed descriptive statistical analysis to examine patient demographics and clinical outcomes. We identified 156 patients meeting criteria between 2005 and 2014. Overall, patients conditioned with Bu/Cy were significantly younger, but more likely to be treated in an earlier era than those receiving Flu/Mel. Regimen choice was not associated with relapse rates (RR), relapse-free survival (RFS), or overall survival (OS) on both univariate and multivariable analyses. Bu/Cy was associated with increased non-relapse mortality (NRM) on multivariable analysis. These findings demonstrate that Flu/Mel provides non-inferior disease control and could be an appropriate regimen for selected patients.

SAMHD1 Promotes DNA End Resection to Facilitate DNA Repair by Homologous Recombination.

DNA double-strand break (DSB) repair by homologous recombination (HR) is initiated by CtIP/MRN-mediated DNA end resection to maintain genome integrity. SAMHD1 is a dNTP triphosphohydrolase, which restricts HIV-1 infection, and mutations are associated with Aicardi-Goutières syndrome and cancer. We show that SAMHD1 has a dNTPase-independent function in promoting DNA end resection to facilitate DSB repair by HR. SAMHD1 deficiency or Vpx-mediated degradation causes hypersensitivity to DSB-inducing agents, and SAMHD1 is recruited to DSBs. SAMHD1 complexes with CtIP via a conserved C-terminal domain and recruits CtIP to DSBs to facilitate end resection and HR. Significantly, a cancer-associated mutant with impaired CtIP interaction, but not dNTPase-inactive SAMHD1, fails to rescue the end resection impairment of SAMHD1 depletion. Our findings define a dNTPase-independent function for SAMHD1 in HR-mediated DSB repair by facilitating CtIP accrual to promote DNA end resection, providing insight into how SAMHD1 promotes genome integrity.

Complexities of TGF-ß targeted cancer therapy.

Many advanced tumors produce excessive amounts of Transforming Growth Factor-ß (TGF-ß) which, in normal epithelial cells, is a potent growth inhibitor. However, in oncogenically activated cells, the homeostatic action of TGF-ß is often diverted along alternative pathways. Hence, TGF-ß signaling elicits protective or tumor suppressive effects during the early growth-sensitive stages of tumorigenesis. However, later in tumor development when carcinoma cells become refractory to TGF-ß-mediated growth inhibition, the tumor cell responds by stimulating pathways with tumor progressing effects. At late stages of malignancy, tumor progression is driven by TGF-ß overload. The tumor microenvironment is a target of TGF-ß action that stimulates tumor progression via pro-tumorigenic effects on vascular, immune, and fibroblastic cells. Bone is one of the richest sources of TGF-ß in the body and a common site for dissemination of breast cancer metastases. Osteoclastic degradation of bone matrix, which accompanies establishment and growth of metastases, triggers further release of bone-derived TGF-ß. This leads to a vicious positive feedback of tumor progression, driven by ever increasing levels of TGF-ß released from both the tumor and bone matrix. It is for this reason, that pharmaceutical companies have developed therapeutic agents that block TGF-ß signaling. Nonetheless, the choice of drug design and dosing strategy can affect the efficacy of TGF-ß therapeutics. This review will describe pre-clinical and clinical data of four major classes of TGF-ß inhibitor, namely i) ligand traps, ii) antisense oligonucleotides, iii) receptor kinase inhibitors and iv) peptide aptamers. Long term dosing strategies with TGF-ß inhibitors may be ill-advised, since this class of drug has potentially highly pleiotropic activity, and development of drug resistance might potentiate tumor progression. Current paradigms for the use of TGF-ß inhibitors in oncology have therefore moved towards the use of combinatorial therapies and short term dosing, with considerable promise for the clinic.

The complexities of TGF-ß action during mammary and squamous cell carcinogenesis.

Many advanced tumors produce excess amounts of Transforming Growth Factor-ß (TGF-ß), which is a potent growth inhibitor of normal epithelial cells. However, in tumors its homeostatic action on cells can be diverted along several alternative pathways. Thus, TGF-ß signaling has been reported to elicit a preventative or tumor suppressive effect during the earlier stages of tumorigenesis, but later in tumor development, when carcinoma cells become refractory to TGF-ß-mediated growth inhibition, response to TGF-ß signaling elicits predominantly tumor progressing effects. This is not a simple switch from suppression to progression, but more like a rheostat, involving multiple complementary and antagonizing activities that slowly tip the balance from one to the other. This review will focus on the multiple activities of TGF-ß in regulation of two epithelial tumor types, namely squamous cell carcinoma and breast cancer. Basic findings in current mouse models of cancer are presented, as well as a discussion of the complicating issue of outcome of altered TGFß signaling depending on genetic variability between mouse strains. This review also discusses the role TGF-ß within the tumor microenvironment particularly its ability to polarize the microenvironment towards a pro-tumorigenic milieu.

Outgrowth of drug-resistant carcinomas expressing markers of tumor aggression after long-term TßRI/II kinase inhibition with LY2109761.

TGF-ß is produced excessively by many solid tumors and can drive malignant progression through multiple effects on the tumor cell and microenvironment. TGF-ß signaling pathway inhibitors have shown efficacy in preclinical models of metastatic cancer. Here, we investigated the effect of systemic LY2109761, a TGF-ß type I/II receptor (TßRI/TßRII) kinase inhibitor, in both a tumor allograft model and the mouse skin model of de novo chemically induced carcinogenesis in vivo. Systemic LY2109761 administration disrupted tumor vascular architecture and reduced myofibroblast differentiation of E4 skin carcinoma cells in a tumor allograft. In the 7,12-dimethyl-benzanthracene plus phorbol myristate acetate-induced skin chemical carcinogenesis model, acute dosing of established naive primary carcinomas with LY2109761 (100 mg/kg) every 8 hours for 10 days (100 mg/kg) diminished phospho-Smad2 (P-Smad2) levels and marginally decreased the expression of inflammatory and invasive markers. Sustained exposure to LY2109761 (100 mg/kg/d) throughout the tumor outgrowth phase had no effect on carcinoma latency or incidence. However, molecular analysis of resultant carcinomas by microarray gene expression, Western blotting, and immunohistochemistry suggests that long-term LY2109761 exposure leads to the outgrowth of carcinomas with elevated P-Smad2 levels that do not respond to drug. This is the first description of acquired resistance to a small-molecule inhibitor of the TßRI/TßRII kinase. Resultant carcinomas were more aggressive and inflammatory in nature, with delocalized E-cadherin and elevated expression of Il23a, laminin V, and matrix metalloproteinases. Therefore, TGF-ß inhibitors might be clinically useful for applications requiring acute administration, but long-term patient exposure to such drugs should be undertaken with caution.

Overexpression of miR-21 promotes an in vitro metastatic phenotype by targeting the tumor suppressor RHOB.

Metastasis is a multistep process that involves the deregulation of oncogenes and tumor suppressors beyond changes required for primary tumor formation. RHOB is known to have tumor suppressor activity, and its knockdown is associated with more aggressive tumors as well as changes in cell shape, migration, and adhesion. This study shows that oncogenic microRNA, miR-21, represses RHOB expression by directly targeting the 3' untranslated region. Loss of miR-21 is associated with an elevation of RHOB in hepatocellular carcinoma cell lines Huh-7 and HepG2 and in the metastatic breast cancer cell line MDA-MB-231. Using in vitro models of distinct stages of metastasis, we showed that loss of miR-21 also causes a reduction in migration, invasion, and cell elongation. The reduction in migration and cell elongation can be mimicked by overexpression of RHOB. Furthermore, changes in miR-21 expression lead to alterations in matrix metalloproteinase-9 activity. Therefore, we conclude that miR-21 promotes multiple components of the metastatic phenotype in vitro by regulating several important tumor suppressors, including RHOB.

Heme oxygenase-2 protects against glutathione depletion-induced neuronal apoptosis mediated by bilirubin and cyclic GMP.

Heme oxygenase (HO) enzymes catalyze the breakdown of heme to iron, carbon monoxide (CO), and biliverdin, which is rapidly converted to bilirubin. HO-2 has been implicated in protection against oxidative stress, ischemia, and traumatic brain injury. The neuroprotective effects of HO-2 have been attributed to the generation of bilirubin, which is an important radical scavenger. However, the mechanism by which HO-2 provides protection is unclear. We utilized the olfactory system as a model to define the roles of HO-2 in glutathione depletion-induced oxidative injury, since olfactory receptor neurons (ORNs) express high levels of HO isoforms. We demonstrated that L-buthionine-[S, R]-sulfoximine (BSO), an inhibitor of glutathione biosynthesis, lowered glutathione levels and induced apoptosis of ORNs. Despite the presence of HO-1 in ORNs, HO-2 null animals displayed increased levels of neuronal death after BSO treatment compared to wild type mice. Levels of bilirubin and cGMP were also reduced in HO-2 null mice. Primary cultures of ORNs confirmed that the neuroprotective role of HO-2 was mediated by bilirubin and cGMP. Taken together, these results suggest that HO-2 plays a major role in neuroprotection from oxidative stress, an effect that is mediated by cGMP and bilirubin.

C75, a fatty acid synthase inhibitor, modulates AMP-activated protein kinase to alter neuronal energy metabolism.

C75, a synthetic inhibitor of fatty acid synthase (FAS), is hypothesized to alter the metabolism of neurons in the hypothalamus that regulate feeding behavior to contribute to the decreased food intake and profound weight loss seen with C75 treatment. In the present study, we characterize the suitability of primary cultures of cortical neurons for studies designed to investigate the consequences of C75 treatment and the alteration of fatty acid metabolism in neurons. We demonstrate that in primary cortical neurons, C75 inhibits FAS activity and stimulates carnitine palmitoyltransferase-1 (CPT-1), consistent with its effects in peripheral tissues. C75 alters neuronal ATP levels and AMP-activated protein kinase (AMPK) activity. Neuronal ATP levels are affected in a biphasic manner with C75 treatment, decreasing initially, followed by a prolonged increase above control levels. Cerulenin, a FAS inhibitor, causes a similar biphasic change in ATP levels, although levels do not exceed control. C75 and cerulenin modulate AMPK phosphorylation and activity. TOFA, an inhibitor of acetyl-CoA carboxylase, increases ATP levels, but does not affect AMPK activity. Several downstream pathways are affected by C75 treatment, including glucose metabolism and acetyl-CoA carboxylase (ACC) phosphorylation. These data demonstrate that C75 modulates the levels of energy intermediates, thus, affecting the energy sensor AMPK. Similar effects in hypothalamic neurons could form the basis for the effects of C75 on feeding behavior.