Amir H. Shahlaee

Malignant peripheral nerve sheath tumor: Molecular pathogenesis and current management considerations

Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are rare tumors that often occur in patients with neurofibromatosis 1. Surgical resection represents the mainstay of treatment. Radiation and chemotherapy have a role in selected patients with MPNST. Accurate pathologic diagnosis remains a challenge in many cases of MPNST. There are many recent advances in the understanding of the molecular pathogenesis of MPNST which represent the best opportunities to develop new strategies for management of patients with MPNST. J. Surg. Oncol. 2008;97:340–349.

Distinct and Shared Transcriptomes Are Regulated by Microphthalmia-Associated Transcription Factor Isoforms in Mast Cells

The Microphthalmia-associated transcription factor (Mitf) is an essential basic helix-loop-helix leucine zipper transcription factor for mast cell development. Mice deficient in Mitf harbor a severe mast cell deficiency, and Mitf-mutant mast cells cultured ex vivo display a number of functional defects. Therefore, an understanding of the genetic program regulated by Mitf may provide important insights into mast cell differentiation. Multiple, distinct isoforms of Mitf have been identified in a variety of cell types; we found that Mitf-a, Mitf-e, and Mitf-mc were the major isoforms expressed in mast cells. To determine the physiologic function of Mitf in mast cells, we restored expression of these isoforms in primary mast cells from Mitf−/− mice. We found that these isoforms restored granular morphology and integrin-mediated migration. By microarray analysis, proteases, signaling molecules, cell surface receptor, and transporters comprised the largest groups of genes up-regulated by all isoforms. Furthermore, we found that isoforms also regulated distinct genes sets, suggesting separable biological activities. This work defines the transcriptome regulated by Mitf in mast cells and supports its role as master regulator of mast cell differentiation. Expression of multiple isoforms of this transcription factor may provide for redundancy of biological activities while also allowing diversity of function.

DEFINITIVE RADIOTHERAPY FOR EWING TUMORS OF EXTREMITIES AND PELVIS: LONG-TERM DISEASE CONTROL, LIMB FUNCTION, AND TREATMENT TOXICITY

PURPOSE More than 70% of Ewing tumors occur in the extremities and pelvis. This study identified factors influencing local control and functional outcomes after management with definitive radiotherapy (RT). PATIENTS AND METHODS A total of 75 patients with a localized Ewing tumor of the extremity or pelvis were treated with definitive RT at the University of Florida between 1970 and 2006 (lower extremity tumors in 30, pelvic tumors in 26, and upper extremity tumors in 19). RT was performed on a once-daily (40%) or twice-daily (60%) basis. The median dose was 55.2 Gy in 1.8-Gy daily fractions or 55.0 Gy in 1.2-Gy twice-daily fractions. The median observed follow-up was 4.7 years. Functional outcome was assessed using the Toronto Extremity Salvage Score. RESULTS The 10-year actuarial overall survival, cause-specific survival, freedom from relapse, and local control rate was 48%, 48%, 42%, and 71%, respectively. Of the 72 patients, 3 required salvage amputation. Inferior cause-specific survival was associated with larger tumors (81% for tumors <8 cm vs. 39% for tumors >/=8 cm, p <0.05). No patient characteristics or treatment variables were predictive of local failure. No fractures occurred in patients treated with hyperfractionation or with tumors of the distal extremities. Severe late complications were more frequently associated with use of <8-MV photons and fields encompassing the entire bone or hemipelvis. A significantly better Toronto Extremity Salvage Score was associated with a late-effect biologically effective dose of <91.7 Gy(3). CONCLUSIONS Limb preservation was effectively achieved through definitive RT. Treating limited field sizes with hyperfractionated high-energy RT could minimize long-term complications and provides superior functional outcomes.

Mast cell transcriptional networks.

Unregulated activation of mast cells can contribute to the pathogenesis of inflammatory and allergic diseases, including asthma, rheumatoid arthritis, inflammatory bowel disease, and multiple sclerosis. Absence of mast cells in animal models can lead to impairment in the innate immune response to parasites and bacterial infections. Aberrant clonal accumulation and proliferation of mast cells can result in a variety of diseases ranging from benign cutaneous mastocytosis to systemic mastocytosis or mast cell leukemia. Understanding mast cell differentiation provides important insights into mechanisms of lineage selection during hematopoiesis and can provide targets for new drug development to treat mast cell disorders. In this review, we discuss controversies related to development, sites of origin, and the transcriptional program of mast cells.

Impact of local management on long-term outcomes in Ewing tumors of the pelvis and sacral bones: the University of Florida experience.

PURPOSE This retrospective analysis describes our 35-year experience with respect to disease control and functional status. PATIENTS AND METHODS Thirty-five patients with localized Ewing tumors of the pelvis and sacral bones were treated from 1970 to 2005. Twenty-six patients were treated with definitive radiotherapy (RT), and 9 patients were treated with combined local therapy in the form of surgery + RT. The median RT dose was 55.2 Gy. The patients who received RT alone were more likely to be older men with larger tumors exhibiting soft-tissue extension. Patients in the definitive RT group were more likely to receive etoposide and ifosfamide or undergo bone marrow transplant. Median potential follow-up was 19.4 years. RESULTS The 15-year actuarial cause-specific survival, freedom from relapse rate, and local control rates were 26% vs. 76% (p = 0.016), 28% vs. 78% (p = 0.015), and 64% vs. 100% (p = 0.087), respectively, for patients treated with definitive RT and combined therapy. Overall, tumors <8 cm had significantly better cause-specific survival, but this was unrelated to local control. The median Toronto Extremity Salvage Score for the definitive RT and combined therapy groups were 99 and 94, respectively (p = 0.19). Seven definitive RT patients (27%) had serious complications. CONCLUSION Combined modality local therapy should be considered if pelvic Ewing tumors are resectable. However, because of the extent of local disease, most patients have unresectable or partially resectable tumors and therefore require RT in some capacity. For this reason, innovative RT strategies are needed to improve long-term disease outcomes and minimize side effects while maintaining an acceptable functional result.

Canine Anatomic Phantom for Preclinical Dosimetry in Internal Emitter Therapy

The majority of investigational studies of new diagnostic and therapeutic radiopharmaceuticals use murine animal models for preclinical assessments of pharmacokinetics and organ radiation dosimetry. Although mice and rats are widely available and relatively inexpensive, their smaller organ anatomy relative to that of humans can lead to considerable differences in organ dosimetry, thus complicating extrapolations of dose–response relationships to human patients. Nonhuman primates circumvent these problems in many respects but are increasingly becoming expensive and limited because of ethical considerations. With the recent completion of the dog genome project and the recognition of many similarities between canine and human cancers, dogs are increasingly being considered in cancer research and drug development. The main objective of this study was to construct a 3-dimensional computational phantom of a large dog on the basis of whole-body multislice CT data. Methods: A female hound cross underwent whole-body contrast-enhanced CT at a 2-mm slice thickness. On completion of the scan, the dog was euthanized, and the entire skeleton was harvested for a subsequent microCT investigation. The CT data were imported into a computational software program and used to create a polygon-mesh phantom of the entire animal. All of the major organs and bones were semiautomatically segmented and tagged to the CT slices. The phantom data were imported into a second software program and transformed to a nonuniform rational basis-spline surface phantom, allowing easy alteration of the phantom to simulate dogs of smaller or larger statures. A voxel-based version of the canine phantom was created by use of an in-house routine for subsequent import into the EGSnrc radiation transport code for photon and β-particle organ dosimetry. Results: The resulting voxel-based version of the canine phantom had a total body mass of 26.0 kg and a total body tissue mass (exclusive of wall organ content) of 24.5 kg. Although this University of Florida (UF) canine phantom displayed a total body mass intermediate between those of the Oak Ridge National Laboratory (ORNL) 5-y and 10-y stylized human phantoms of the MIRDOSE and OLINDA software codes, considerable differences were noted in organ photon cross-doses. For example, ratios of the specific absorbed fraction Φ(lungs ← liver)UF Dog to Φ(lungs ← liver)ORNL 5-y ranged from ∼30 at 10 keV to ∼3.5 at 1 MeV. Corresponding ratios of Φ(lungs ← liver)UF Dog to Φ(lungs ← liver)ORNL 10-y ranged from ∼6 at 10 keV to ∼1.3 at 1 MeV. Conversely, values of Φ(kidneys ← spleen) and Φ(liver ← spleen) were noted to be much lower (factors of 2–4) and much higher (factors of 2–15), respectively, in the canine phantom than in the ORNL human phantoms. These differences were attributed more to organ shape and position within the torso than to organ mass, because many of the canine organs closely approximated their counterparts volumetrically in the stylized pediatric human phantoms. Conclusion: The use of canine models, particularly in spontaneously occurring malignancies such as osteosarcoma, for preclinical testing of antineoplastic agents offers significant advantages over current murine models. However, the development of canine-specific technology is critical to the optimization of these studies. The UF canine dosimetry phantom described here aims to solve problems that could stem from the use of current human dosimetry models during radiopharmaceutical research.

Spinal and Paraspinal Ewing Tumors

PURPOSE To perform a review of the 40-year University of Florida experience treating spinal and paraspinal Ewing tumors. PATIENTS AND METHODS A total of 27 patients were treated between 1965 and 2007. For local management, 21 patients were treated with radiotherapy (RT) alone and 6 with surgery plus RT. All patients with metastatic disease were treated with RT alone. The risk profiles of each group were otherwise similar. The median age was 17 years, and the most frequent subsite was the sacral spine (n = 9). The median potential follow-up was 16 years. RESULTS The 5-year actuarial overall survival, cause-specific survival, and local control rate was 62%, 62%, and 90%, respectively. For the nonmetastatic subset (n = 22), the 5-year overall survival, cause-specific survival, and local control rate was 71%, 71%, and 89%, respectively. The local control rate was 84% for patients treated with RT alone vs. 100% for those treated with surgery plus RT. Patients who were >14 years old and those who were treated with intensive therapy demonstrated superior local control. Of 9 patients in our series with Frankel C or greater neurologic deficits at presentation, 7 experienced a full recovery with treatment. Of the 27 patients, 37% experienced Common Toxicity Criteria Grade 3 or greater toxicity, including 2 deaths from sepsis. CONCLUSION Aggressive management of spinal and paraspinal Ewing tumors with RT with or without surgery results in high toxicity but excellent local control and neurologic outcomes. Efforts should be focused on identifying disease amenable to combined modality local therapy and improving RT techniques.

Verification of association of elevated serum IDO enzyme activity with acute rejection and low CD4-ATP levels with infection.

Background Both acute rejection (AR) and major infection events (MIE) can reduce long-term allograft survival. We assessed the simultaneous efficacy of serum and urine biomarker indoleamine 2,3-dioxygenase (IDO) enzyme activity and peripheral blood CD4-ATP levels for AR and MIE association, respectively. Methods We prospectively tested 217 blood and 167 urine serial samples, collected monthly for 12 months after transplantation from 29 consecutive children receiving a kidney transplant. The indoleamine 2,3-dioxygenase activity was assessed by mass spectrometry assays using the ratio of product L-kynurenine (kyn) to substrate tryptophan (trp). Kyn/trp ratios and blood CD4 T-cell ATP levels were correlated with AR, MIE, or stable group (no events) in the next 30 days. Results Using absolute cutoffs and allocating to samples to AR, MIE, or stable group, mean serum kyn/trp ratios were significantly elevated in the group that experienced AR (P=0.0007). Similarly, peripheral blood CD4-ATP levels were significantly lower in the group experiencing MIE (P=0.0351). Urine kyn/trp ratios and blood tacrolimus levels were not different between AR and stable groups. Within-subject analyses, accounting for repeated measures in subjects, also showed that, over time, serum kyn/trp ratios were higher before AR (P=0.031) and blood CD4-ATP levels were lower before MIE (P=0.008). Conclusions These results from our pilot discovery group suggest that a panel of biomarkers together can predict overimmunosuppression or underimmunosuppression. Further independent validation in a multicenter cohort is suggested.

PU.1 Positively Regulates GATA-1 Expression in Mast Cells

Coexpression of PU.1 and GATA-1 is required for proper specification of the mast cell lineage; however, in the myeloid and erythroid lineages, PU.1 and GATA-1 are functionally antagonistic. In this study, we report a transcriptional network in which PU.1 positively regulates GATA-1 expression in mast cell development. We isolated a variant mRNA isoform of GATA-1 in murine mast cells that is significantly upregulated during mast cell differentiation. This isoform contains an alternatively spliced first exon (IB) that is distinct from the first exon (IE) incorporated in the major erythroid mRNA transcript. In contrast to erythroid and megakaryocyte cells, in mast cells we show that PU.1 and GATA-2 predominantly occupy potential cis-regulatory elements in the IB exon region in vivo. Using reporter assays, we identify an enhancer flanking the IB exon that is activated by PU.1. Furthermore, we observe that in PU.1−/− fetal liver cells, low levels of the IE GATA-1 isoform is expressed, but the variant IB isoform is absent. Reintroduction of PU.1 restores variant IB isoform and upregulates total GATA-1 protein expression, which is concurrent with mast cell differentiation. Our results are consistent with a transcriptional hierarchy in which PU.1, possibly in concert with GATA-2, activates GATA-1 expression in mast cells in a pathway distinct from that seen in the erythroid and megakaryocytic lineages.

Immune biomarker panel monitoring utilizing IDO enzyme activity and CD4 ATP levels: prediction of acute rejection vs. viral replication events.

Dharnidharka VR, Gupta S, Al Khasawneh E, Haafiz A, Shuster JJ, Theriaque DW, Shahlaee AH, Garrett TJ. Immune biomarker panel monitoring utilizing IDO enzyme activity and CD4 ATP levels: Prediction of acute rejection vs. viral replication events.
Pediatr Transplantation 2011: 15: 321–328.