Effect of External Beam Radiation Therapy (EBRT) and Brachytherapy (BT) on Circulating MDSC Populations in Patients Treated Definitively for Cervical Cancer

PURPOSE/OBJECTIVE(S)

The immunosuppressive function of myeloid derived suppressor cells (MDSCs) has been implicated in the regulation of immune responses against cancer. MDSCs have been associated with progression and poor response to therapy in various types of cancer, including cervical cancer. Radiation treatment (RT) alters immune cell populations within the tumor and is thought to augment antitumor responses. However, whether RT also recruits immunosuppressive MDSC populations is not well understood. Here, we investigate how circulating MDSC populations change in response to RT and if changes in MDSC frequency or subsets is predictive of RT responses in cervical cancer patients.

MATERIALS/METHODS

Newly diagnosed, treatment-naïve pts with locally advanced carcinoma of the cervix will be enrolled from July 2022 to July 2023. EBRT to the pelvis was delivered at a dose of 45 Gy in 25 fractions with a simultaneous integrated boost of 52-55 Gy to involved regional lymph nodes and parametria and concurrent weekly cisplatin. Gross tumor was boosted via interstitial or tandem ring BT (22.5-27.5 Gy) after completion of EBRT. Serial blood samples were collected prior to initiating therapy (T0), post-EBRT and pre-BT (T1), and one-month post-BT (T2). Treatment response was determined based on pre-treatment MRI compared to MRI post-EBRT. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using density gradient centrifugation and stained for analysis via flow cytometry. MDSC populations were identified by Live/Dead-CD11b+CD33+HLA-DR- staining. MDSC subsets were further subdivided into granulocytic (G-, CD15+CD14-), monocytic (M-, CD15-CD14+), or early-MDSCs (e-, CD15-CD14-).

RESULTS

Blood samples were collected at indicated time points for four patients (FIGO stage IIA-IIB). Three had partial responses to chemoradiotherapy (CRT), while one had a complete response. All three patients with partial response had an increase in total frequency of circulating MDSCs in response to EBRT/BT (mean %fx MDSC 16.6 at T0 to 35.9 at T2), and an increase in total MDSCs in two of these patients occurred with EBRT alone. Interestingly, the patient that had a complete response had fewer MDSCs at T2 relative to T0 (35.8% at T0 to 27% at T2). Proportion of MDSC subsets varied considerably among the patients, and all had altered distribution of subsets in response to RT. G-MDSCs expanded the most to RT while M-MDSCs and e-MDSCs were less affected (mean fold change from T0 to T2 G-MDSC 4.75, M-MDSC 1.27, e-MDSC 0.942).

CONCLUSION

In this cohort of patients, an increase in MDSC frequency occurred after RT and altered subset distribution. Only the patient with a complete response had fewer total MDSCs following completion of CRT, suggesting further studies are needed to determine if circulating MDSCs could be a biomarker for treatment response to RT in cervical cancer.

Thrombin and leukocyte recruitment in endotoxemia

Because thrombin has been implicated in sepsis, it has been proposed that antithrombin III (AT III) is beneficial due to its anticoagulatory and antiadhesive effects. Using intravital microscopy, we visualized leukocyte-endothelium interactions in postcapillary venules of the feline mesentery exposed to lipopolysaccharide (LPS). At a concentration of AT III that blocks leukocyte adhesion in postischemic mesentery, we found no role for thrombin in LPS-induced rolling, adhesion and emigration, or microvascular dysfunction. Furthermore, AT III did not attenuate leukocyte-endothelial interactions after tumor necrosis factor-alpha superfusion of the mesentery. In contrast, fucoidan, a selectin inhibitor, prevented almost all LPS-induced rolling and reduced adhesion, emigration, and microvascular dysfunction. In a model of endotoxemia, leukocyte recruitment into mesentery or lungs was unaffected by AT III. Finally, in a human cell system that mimics the flow conditions in vivo, human neutrophils rolled, adhered, and emigrated similar to the feline postcapillary microvessels, and AT III had no effect on leukocyte recruitment induced by LPS. If AT III has beneficial effects in endotoxemia, it is not due to a direct effect upon leukocyte rolling, adhesion, or emigration in postcapillary venules in vivo.

Undiluted albuterol aerosols in the pediatric emergency department

OBJECTIVE

To evaluate the efficacy and efficiency of a short treatment method of administering albuterol aerosols.

METHODS

Fifty children 6 to 18 years of age with severe acute asthma (peak flow rates <60% of predicted) were enrolled in a single-blind, controlled trial in an urban pediatric emergency department. Patients were randomized to receive either the study short treatment (3.5 mL of undiluted albuterol nebulized for 20 inhalations) or the control treatment (albuterol diluted [.5 mL] and nebulized in normal saline [3 mL]) every 20 minutes for a total of 3 treatments. Peak flow and spirometric measurements were performed before and after each treatment.

RESULTS

There were 25 patients in the study group and 25 in the control group. There were no demographic differences between groups; both had comparable pulmonary function at presentation. The mean forced expiratory volume in 1 second percent predicted improvement between 0 and 60 minutes was 18.8% in the study group and 14.5% in the control group. The total time of treatment delivery for the study group was 6.4 minutes versus 32.7 minutes for the control group.

CONCLUSION

Undiluted albuterol short treatments seem to be as effective as standard diluted albuterol in severe asthmatics, while offering the ease and efficiency of shorter treatment administration time.

The functional paradox of CD43 in leukocyte recruitment: a study using CD43-deficient mice

Although there is considerable evidence implicating a role for CD43 (leukosialin) in leukocyte cell-cell interactions, its precise function remains uncertain. Using CD43-deficient mice (CD43(-/-)) and intravital microscopy to directly visualize leukocyte interactions in vivo, we investigated the role of CD43 in leukocyte-endothelial cell interactions within the cremasteric microcirculation under flow conditions. Our studies demonstrated significantly enhanced leukocyte rolling and adhesion after chemotactic stimuli in CD43(-/-) mice compared with wild type mice. Using an in vitro flow chamber, we established that the enhanced rolling interactions of CD43(-/-) leukocytes, primarily neutrophils, were also observed using immobilized E-selectin as a substrate, suggesting that passive processes related to steric hindrance or charge repulsion were likely mechanisms. Despite increased adhesion and rolling interactions by CD43(-/-) leukocytes, we uncovered a previously unrecognized impairment of CD43(-/-) leukocytes to infiltrate tissues. Oyster glycogen-induced neutrophil and monocyte infiltration into the peritoneum was significantly reduced in CD43(-/-) mice. In response to platelet activating factor, CD43(-/-) leukocytes were impaired in their ability to emigrate out of the vasculature. These results suggest that leukocyte CD43 has a dual function in leukocyte-endothelial interactions. In addition to its role as a passive nonspecific functional barrier, CD43 also facilitates emigration of leukocytes into tissues.

Antithrombin and ischemia/reperfusion

Acute inflammation, a localized response that occurs in various diseases, is characterized by neutrophil infiltration into tissues. This process requires neutrophils to initially tether and roll along the endothelium of postcapillary venules before undergoing firm adhesion and emigration out of the vasculature into the tissues. Recently, thrombin has been implicated at multiple sites in the inflammatory cascade, and may represent an important link between inflammation and thrombosis. Our recent studies demonstrate that thrombin is an important mediator of neutrophil-dependent injury in ischemia-reperfusion injury. Furthermore, antithrombin concentrate may be therapeutically efficacious in ischemia-reperfusion injury, as it is capable of attenuating the thrombin-mediated effects on neutrophil-endothelial interactions.

Antithrombin III prevents and rapidly reverses leukocyte recruitment in ischemia/reperfusion

BACKGROUND

P-selectin has recently been shown to be essential for leukocyte rolling after the reperfusion of ischemic mesentery. However, the mediators responsible for neutrophil rolling in ischemic microvessels remain entirely unclear.

METHODS AND RESULTS

Intravital microscopy was used to examine leukocyte kinetics in a feline mesentery ischemia/reperfusion model. Sixty minutes of ischemia followed by reperfusion caused a profound increase in leukocyte rolling and adhesion. Pretreatment with the endogenous antithrombotic agent antithrombin III (ATIII) infused as a bolus (250 U/kg) reduced neutrophil rolling and adhesion to preischemic levels during reperfusion. No effect was seen with heat-inactive ATIII. Importantly, ATIII posttreatment also significantly reduced neutrophil rolling and adhesion during reperfusion, suggesting that ATIII can reverse the leukocyte recruitment response induced by ischemia/reperfusion. Vascular permeability was also reduced by 50% after ATIII administration. To determine whether ATIII could reverse thrombin-induced rolling directly, neutrophil rolling was performed on human endothelium in flow chambers. Indeed, thrombin-induced rolling, but not histamine-induced rolling, could be rapidly reversed with ATIII on endothelium, suggesting that ATIII affects thrombin rather than directly affecting neutrophils or the endothelium.

CONCLUSIONS

This study demonstrates for the first time that thrombin plays an important role in ischemia-induced leukocyte rolling and adhesion and that ATIII can be used therapeutically postreperfusion to attenuate the leukocyte recruitment response in inflammation without the nonspecific effects associated with anti-adhesion molecule therapy.