Risk of corticosteroid treatment and hospitalization after checkpoint inhibitor and radiation therapy in patients with cancer.

BACKGROUND: Immune checkpoint inhibitors (ICIs) are potent new cancer therapies but can cause serious immune-related adverse events. ICIs have contributed significantly to improved survival and thereby provide more opportunity for the development of local disease symptomatology requiring palliative radiation. Radiation therapy (RT) has also recently shown benefit in the oligometastatic setting. Data on the interaction and safety of concurrent ICIs and RT are limited. METHODS: In this retrospective cohort study using a large medical claims database from 2010 to 2017, the need for corticosteroid therapy and the risk of hospitalization within 180 days of treatment with an ICI were determined for patients with a diagnosis of malignant melanoma or lung cancer. Patients were stratified by the use of RT within the 30 days before and after ICI therapy. RESULTS: In all, 2020 patients (218 with RT and 1802 without RT) met the inclusion criteria for prednisone analysis, whereas 3519 patients (361 with RT and 3158 without RT) met the inclusion criteria for all other analyses. In a univariable analysis, RT was not associated with the need for prednisone (relative risk [RR], 1.2; 95% confidence interval [CI], 0.8-1.9) or methylprednisolone (RR, 1.1; 95% CI, 0.7-2.0). When the end point was hospitalization, RT was significantly associated with hospitalization after ICI therapy for certain cancer/drug combinations (RR for lung cancer/programmed death 1 receptor inhibitors, 1.4; 95% CI, 1.2-1.6; P < .001; RR for melanoma/ipilimumab, 2.0; 95% CI, 1.0-3.5; P = .03). CONCLUSIONS: In patients treated with ICIs, receiving RT was not associated with a higher risk of requiring corticosteroid therapy in comparison with not receiving RT. However, RT was associated with a higher risk of hospitalization, although this finding may be a result of differences in the underlying patient illness severity or oncologic disease burden at the baseline. LAY SUMMARY: Data on the interaction of immunotherapy (immune checkpoint inhibitors) and radiation therapy and the safety of combining them are limited. Using a large database, this study has found that patients treated concurrently with immune checkpoint inhibitors and radiation therapy are not at increased risk for requiring corticosteroid therapy (which is used as a proxy for immune-related adverse events). However, concurrent therapy is associated with a higher risk of hospitalization, although this finding may be due to differences in the underlying patient illness severity (sicker patients may require both immunotherapy and radiation therapy).

Organellar vs cellular control of mitochondrial dynamics.

Mitochondrial dynamics, the fusion and fission of individual mitochondrial units, is critical to the exchange of the metabolic, genetic and proteomic contents of individual mitochondria. In this regard, fusion and fission events have been shown to modulate mitochondrial bioenergetics, as well as several cellular processes including fuel sensing, ATP production, autophagy, apoptosis, and the cell cycle. Regulation of the dynamic events of fusion and fission occur at two redundant and interactive levels. Locally, the microenvironment of the individual mitochondrion can alter its ability to fuse, divide or move through the cell. Globally, nuclear-encoded processes and cellular ionic and second messenger systems can alter or activate mitochondrial proteins, regulate mitochondrial dynamics and concomitantly change the condition of the mitochondrial population. In this review we investigate the different global and local signals that control mitochondrial biology. This discussion is carried out to clarify the different signals that impact the status of the mitochondrial population.

Mitochondrial transporter ATP binding cassette mitochondrial erythroid is a novel gene required for cardiac recovery after ischemia/reperfusion.

BACKGROUND: Oxidative stress and mitochondrial dysfunction are central mediators of cardiac dysfunction after ischemia/reperfusion. ATP binding cassette mitochondrial erythroid (ABC-me; ABCB10; mABC2) is a mitochondrial transporter highly induced during erythroid differentiation and predominantly expressed in bone marrow, liver, and heart. Until now, ABC-me function in heart was unknown. Several lines of evidence demonstrate that the yeast ortholog of ABC-me protects against increased oxidative stress. Therefore, ABC-me is a potential modulator of the outcome of ischemia/reperfusion in the heart. METHODS AND RESULTS: Mice harboring 1 functional allele of ABC-me (ABC-me(+/-)) were generated by replacing ABC-me exons 2 and 3 with a neomycin resistance cassette. Cardiac function was assessed with Langendorff perfusion and echocardiography. Under basal conditions, ABC-me(+/-) mice had normal heart structure, hemodynamic function, mitochondrial respiration, and oxidative status. However, after ischemia/reperfusion, the recovery of hemodynamic function was reduced by 50% in ABC-me(+/-) hearts as a result of impairments in both systolic and diastolic function. This reduction was associated with impaired mitochondrial bioenergetic function and with oxidative damage to both mitochondrial lipids and sarcoplasmic reticulum calcium ATPase after reperfusion. Treatment of ABC-me(+/-) hearts with the superoxide dismutase/catalase mimetic EUK-207 prevented oxidative damage to mitochondria and sarcoplasmic reticulum calcium ATPase and restored mitochondrial and cardiac function to wild-type levels after reperfusion. CONCLUSIONS: Inactivation of 1 allele of ABC-me increases the susceptibility to oxidative stress induced by ischemia/reperfusion, leading to increased oxidative damage to mitochondria and sarcoplasmic reticulum calcium ATPase and to impaired functional recovery. Thus, ABC-me is a novel gene that determines the ability to tolerate cardiac ischemia/reperfusion.

Abcb10 physically interacts with mitoferrin-1 (Slc25a37) to enhance its stability and function in the erythroid mitochondria.

Mitoferrin-1 (Mfrn1; Slc25a37), a member of the solute carrier family localized in the mitochondrial inner membrane, functions as an essential iron importer for the synthesis of mitochondrial heme and iron-sulfur clusters in erythroblasts. The biochemistry of Mfrn1-mediated iron transport into the mitochondria, however, is poorly understood. Here, we used the strategy of in vivo epitope-tagging affinity purification and mass spectrometry to investigate Mfrn1-mediated mitochondrial iron homeostasis. Abcb10, a mitochondrial inner membrane ATP-binding cassette transporter highly induced during erythroid maturation in hematopoietic tissues, was found as one key protein that physically interacts with Mfrn1 during mouse erythroleukemia (MEL) cell differentiation. Mfrn1 was shown previously to have a longer protein half-life in differentiated MEL cells compared with undifferentiated cells. In this study, Abcb10 was found to enhance the stabilization of Mfrn1 protein in MEL cells and transfected heterologous COS7 cells. In undifferentiated MEL cells, cotransfected Abcb10 specifically interacts with Mfrn1 to enhance its protein stability and promote Mfrn1-dependent mitochondrial iron importation. The structural stabilization of the Mfrn1-Abcb10 complex demonstrates a previously uncharacterized function for Abcb10 in mitochondria. Furthermore, the binding domain of Mfrn1-Abcb10 interaction maps to the N terminus of Mfrn1. These results suggest the tight regulation of mitochondrial iron acquisition and heme synthesis in erythroblasts is mediated by both transcriptional and posttranslational mechanisms, whereby the high level of Mfrn1 is stabilized by oligomeric protein complexes.

Increased rates of immunosuppressive treatment and hospitalization after checkpoint inhibitor therapy in cancer patients with autoimmune disease.

BACKGROUND: Immune checkpoint inhibitors (ICIs) are important new therapeutic options for the treatment of malignancy. Existing data on the relative safety of ICI treatment in patients with pre-existing autoimmune disease (AID) are limited. METHODS: In this retrospective study utilizing an oncology medical claims database, we determined the rates of treatment with immunosuppressive agents and hospitalization within 180 days of treatment with ICIs (pembrolizumab, nivolumab, and ipilimumab) in patients both with and without AID. Patients had diagnoses of either malignant melanoma or lung cancer. Immunosuppressive agents evaluated included oral prednisone and intravenous methylprednisolone. RESULTS: 124 cancer patients with AID and 1896 cancer patients without AID met inclusion criteria for oral prednisone analysis, while 284 patients with AID and 3230 patients without AID met inclusion criteria for all other analyzes. Following treatment with PD-1 inhibitors, rates of treatment with both oral prednisone and intravenous methylprednisolone within 180 days of ICI treatment were significantly increased in the AID group relative to the control group (oral prednisone: 16.7% treatment in AID vs 8.3% in non-AID, p=0.0048; intravenous methylprednisolone: 8.4% treatment in AID vs 3.7% in non-AID, p=0.0012). Rates of hospitalization were significantly increased in melanoma patients with AID relative to melanoma patients without AID following treatment with PD-1 inhibitors (24.1% in AID vs 5.8% in non-AID, p<0.0001). CONCLUSION: Cancer patients with AID have higher rates of hospitalization and treatment with immunosuppressive agents following treatment with ICI therapy compared with patients with no AID. This suggests that patients with AID may have increased toxicity risk while being treated with checkpoint inhibitor therapy. Further prospective clinical trials are needed to determine safety.

Mitochondrial fusion, fission and autophagy as a quality control axis: the bioenergetic view.

The mitochondrial life cycle consists of frequent fusion and fission events. Ample experimental and clinical data demonstrate that inhibition of either fusion or fission results in deterioration of mitochondrial bioenergetics. While fusion may benefit mitochondrial function by allowing the spreading of metabolites, protein and DNA throughout the network, the functional benefit of fission is not as intuitive. Remarkably, studies that track individual mitochondria through fusion and fission found that the two events are paired and that fusion triggers fission. On average each mitochondrion would go though approximately 5 fusion:fission cycles every hour. Measurement of Deltapsi(m) during single fusion and fission events demonstrates that fission may yield uneven daughter mitochondria where the depolarized daughter is less likely to become involved in a subsequent fusion and is more likely to be targeted by autophagy. Based on these observations we propose a mechanism by which the integration of mitochondrial fusion, fission and autophagy forms a quality maintenance mechanism. According to this hypothesis pairs of fusion and fission allow for the reorganization and sequestration of damaged mitochondrial components into daughter mitochondria that are segregated from the networking pool and then becoming eliminated by autophagy.

UCP2 modulates cell proliferation through the MAPK/ERK pathway during erythropoiesis and has no effect on heme biosynthesis.

UCP2, an inner membrane mitochondrial protein, has been implicated in bioenergetics and reactive oxygen species (ROS) modulation. High levels of UCP2 mRNA were recently found in erythroid cells where UCP2 is hypothesized to function as a facilitator of heme synthesis and iron metabolism by reducing ROS production. We examined UCP2 protein expression and role in mice erythropoiesis in vivo. UCP2 was mainly expressed at early stages of erythroid maturation when cells are not fully committed in heme synthesis. Iron incorporation into heme was unaltered in reticulocytes from UCP2-deficient mice. Although heme synthesis was not influenced by UCP2 deficiency, mice lacking UCP2 had a delayed recovery from chemically induced hemolytic anemia. Analysis of progenitor cells from bone marrow and fetal liver both in vitro and in vivo revealed that UCP2 deficiency results in a significant decrease in cell proliferation at the erythropoietin-dependent phase of erythropoiesis. This was accompanied by reduction in the phosphorylated form of ERK, a ROS-dependent cytosolic regulator of cell proliferation. Analysis of ROS in UCP2 null erythroid cells revealed altered distribution of ROS, resulting in decreased cytosolic and increased mitochondrial ROS. Restoration of the cytosol oxidative state of erythroid progenitor cells by the pro-oxidant Paraquat reversed the effect of UCP2 deficiency on cell proliferation in in vitro differentiation assays. Together, these results indicate that UCP2 is a regulator of erythropoiesis and suggests that inhibition of UCP2 function may contribute to the development of anemia.