Myeloid-Derived Cells in Tumors: Effects of Radiation

The discrepancy between the in vitro and in vivo response to radiation is readily explained by the fact that tumors do not exist independently of the host organism; cancer cells grow in the context of a complex microenvironment composed of stromal cells, vasculature, and elements of the immune system. As the antitumor effect of radiotherapy depends in part on the immune system, and myeloid-derived cells in the tumor microenvironment modulate the immune response to tumors, it follows that understanding the effect of radiation on myeloid cells in the tumor is likely to be essential for comprehending the antitumor effects of radiotherapy. In this review, we describe the phenotype and function of these myeloid-derived cells, and stress the complexity of studying this important cell compartment owing to its intrinsic plasticity. With regard to the response to radiation of myeloid cells in the tumor, evidence has emerged demonstrating that it is both model and dose dependent. Deciphering the effects of myeloid-derived cells in tumors, particularly in irradiated tumors, is key for attempting to pharmacologically modulate their actions in the clinic as part of cancer therapy

Peptide Binding and Immunological Properties of the Molecular Chaperonin TRiC

Many heat shock proteins (HSPs) bind antigenic peptides inside cells, and these HSP-peptide complexes are essential for endogenous antigen processing for presentation on major histocompatibility complex class I (MHC I). They have also been suggested to mediate the transfer of antigen to antigen presenting cells (APCs) for cross priming of cytotoxic T lymphocytes (CTLs) against the chaperoned peptides. The TCP-1 Ring Complex (TRiC) is a eukaryotic homologue of hsp60 that has been shown to bind and protect extended antigenic peptides during processing for presentation on MHC I. However, the role of TRiC in cross priming has been heretofore uninvestigated. My hypothesis is that TRiC behaves like the other peptide binding chaperones in both its peptide binding properties and its interactions with APCs as a facilitator of cross priming. The data in this thesis demonstrate that TRiC binds to antigenic peptides in vitro and characterize the biochemical parameters of that binding. These data also demonstrate that in vitro reconstituted TRiC-peptide complexes facilitate the cross priming of CTLs specific for the TRiC chaperoned peptides. TRiC binds to APCs in vitro, and chaperoned peptides are processed and presented on MHC I. These observations provide a plausible mechanism for cross priming of peptides chaperoned by TRiC. However, while TRiC can effectively chaperone peptides into APCs for cross priming, the data here suggest that TRiC does not bind sufficient quantities of antigenic peptide inside the cell to facilitate cross presentation or cross priming of these endogenously bound peptides.

Resection Followed by Involved-Field Fractionated Radiotherapy in the Management of Single Brain Metastasis

Introduction: We expanded upon our previous experience using involved-field fractionated radiotherapy (IFRT) as an alternative to whole brain radiotherapy (WBRT) or stereotactic radiosurgery (SRS) for patients with surgically resected brain metastases.Material and Methods: All patients with single brain metastases who underwent surgical resection followed by IFRT at our institution from 2006-2013 were evaluated. Local recurrence-free survival, distant failure-free survival and overall survival were determined. Analyses were performed associating clinical variables with local recurrence and distant failure. Salvage approaches and toxicity of treatment for each patient were also assessed.Results: Median follow-up was 19.1 months. Fifty-six patients were treated with a median dose of 40.05 Gy/15 fractions with IFRT to the resection cavity. Local recurrence-free survival was 91.4%, distant failure-free survival was 68.4%, and overall survival was 77.7% at 12 months. No variables were associated with increased local recurrence, however melanoma histopathology and infratentorial location were associated with distant failure on multivariate analysis. Local recurrences were salvaged in 5/8 patients, and distant failures were salvaged in 24/29 patients. Two patients developed radionecrosis.Conclusions: Adjuvant IFRT is feasible and safe for well-selected patients with surgically resected single brain metastases. Acceptable rates of local control and salvage of distal intracranial recurrences continue to be achieved with continued follow-up

Fig 10 -

Physiological measures in irradiated and control rats in the neostriatum (A-E) and hippocampus (F). A. For TH there was no overall difference between irradiated groups and controls, but there was an exposure × sex interaction. There were no differences in males whereas the FLASH females, regardless of dose, had increased TH levels compared with control females. B. For DAT the 5-Conv group had increased levels of DAT compared with the controls. C. For DRD1 there was an increase in receptor levels for the groups that received 8 Gy, regardless of dose rate, compared with controls. D. There was an exposure × sex interaction. There were no differences in males, whereas the 8-FLASH females had increased DRD1 levels compared with control females. ELISA was used for Panels A-D, N = 8/sex/exposure. E. There were no differences in DRD2 in the neostriatum. F. There were no differences for NMDA-R1 in the hippocampus. Westerns were used for panels E-F, N = 6-7/sex/exposure.</p

Body weights [g (mean ± SEM)] of proton irradiated and control rats.

A. The overall effect on body weights by exposure group, averaged across sex and week. B. Body weights of females by weeks. C. Body weights of males by weeks. While there was an exposure × sex interaction, both females and males dosed with 8 Gy were lighter than controls. See text for a summary of the exposure × age interaction. ***p < 0.001 compared with controls. N = 14-19/sex/exposure at each week. Due to scheduling errors some of the body weights were missed on some weeks.</p

Conditioned freezing [beam interruptions (mean ± SEM)] for proton irradiated and control rats.

A. Day 1 habituation phase and conditioning phase; there were no differences between the irradiated groups and controls. B. Day 2 contextual learning phase; there were no differences between irradiated groups and controls. C. Day 3 extinction phase for the tone on trials; no differences between groups. D. Day 4 reinstatement phase; no differences were noted. N = 16-19/exposure/sex. Several rats escaped the test arena during the conditioning phase and their data were not used.</p

Locomotor activity [beam breaks (mean ± SEM)] of proton irradiated and control rats.

A. Effects on ambulation by exposure, averaged across sex and test interval (time). No differences in irradiated groups compared with controls. B. Ambulation by test interval with males and females combined. C. Effects on center ambulation by exposure, averaged across sex and time. All irradiated groups with the exception of the 5-FLASH group had reduced center ambulation compared with controls. D. Center ambulation by test interval with males and females combined. *p < 0.05 compared with controls. N = 19/sex/exposure except control male = 17 and 5-FLASH male and female = 18.</p