Transforming activity of the chimeric sequence formed by the fusion of collagen gene COL1A1 and the platelet derived growth factor b-chain gene in dermatofibrosarcoma protuberans

Dermatofibrosarcoma Protuberans in a 12-Year-Old Child: A Rare Case

Dermatofibrosarcoma protuberans (DFSP) is an uncommon soft tissue tumor involving the dermis and subcutaneous fat that rarely occurs in children, manifested as a slowly growing firm plaque on the trunk. A 12-year-old girl patient presented with dark patch on the nasal root after finishing 25 sessions of radiotherapy. Initially, patient came to Oncology Surgery Clinic at Hasan Sadikin General Hospital Bandung with the chief complaint of a large exophytic mass located in the nasal area, which was neither itchy nor painful. A large, firm, painless mass with no sign of localized heat or redness was found on physical examination. There were no palpable cervical or axillary lymph nodes. Wide local excision and frontal flap procedure were performed by Oncology Surgery Department leaving a pedicle with 2×1.5×1 cm on size was observed. Upon histopathological examination, tumor mass was found in the subepithelium and consisted of oval to spindle-shaped cells that were hyperplastic, compacted, diffuse, forming fasciculus, whorled, and cartwheel. Cell nuclei were pleomorphic (oval to wavy), hyperchromatic, with clear nucleolus, and occasion mitotic figures. Hyalinisation was seen between the tumor masses. On immunohistochemical stains, there were diffuse positivity for epithelial membrane antigen (EMA) and vimentin. Based on the histological and immunohistochemical findings, the diagnosis of stage II DFSP was made. Until now, there is no established algorithm for treatment of DFSP. Wide local excision and radiotherapy for 25 sessions was performed on this patient, resulting in complete tumor mass removal. After three months of observation, the second surgery was done to remove a pedicle; however, there is no recurrence of tumor growth. Despite its rarity, DFSP should be considered as a differential diagnosis to avoid underdiagnosis or misdiagnosis.

Novel TNC-PDGFD fusion in fibrosarcomatous dermatofibrosarcoma protuberans: a case report

Background

Dermatofibrosarcoma protuberans (DFSP) is a superficial fibroblastic tumor characterized by high rate of local recurrence and low metastatic potential. Fibrosarcomatous transformation can rarely arise in DFSP either de novo or as recurrent, which represents a form of tumor progression and carries an increased risk of metastasis over classic DFSP. Cytogenetically, DFSP is characterized by a recurrent unbalanced chromosome translocation t (17;22)(q22;q13), leading to the formation of COL1A1-PDGFB fusion transcript that is present in more than 90% of cases. Alternative fusions involving the PDGFD with partners of COL6A3 or EMILIN2 have recently been documented in less than 2% of cases. Herein, we report a DFSP with fibrosarcomtous morphology harboring a novel TNC-PDGFD fusion.

Case presentation

A 54-year-old female presented with a slowly growing mass in the right thigh. Excision demonstrated a 2-cm ovoid, well-circumscribed, gray-white, mass. Microscopic examination revealed a partially encapsulated subcutaneous nodule without dermal connection. The neoplasm was composed of cellular and fairly uniform spindle cells with brisk mitoses, arranged in elongated fascicles and herringbone patterns, with focal collagenized stroma. The neoplastic cells were positive for CD34 and smooth muscle actin. Fluorescence in-situ hybridization analyses showed negative for COL1A1-PDGFB fusion as well as NTRK1/2/3 rearrangements. A subsequent RNA sequencing detected an in-frame fusion between exon 15 of TNC and exon 6 of PDGFD. This fusion was further confirmed by nested reverse transcription polymerase chain reaction amplification followed by Sanger sequencing. A diagnosis of fibrosarcomatous DFSP was rendered and the patient was in good status at a follow-up of 12 months after the operation.

Conclusions

We report a fibrosarcomatous DFSP with novel TNC-PDGFD fusion, which adds to the pathologic and genetic spectrum of PDGFD-rearranged DFSP.

Novel COL4A1-VEGFD gene fusion in myofibroma

Myofibroma is a benign pericytic tumour affecting young children. The presence of multicentric myofibromas defines infantile myofibromatosis (IMF), which is a life‐threatening condition when associated with visceral involvement. The disease pathophysiology remains poorly characterized. In this study, we performed deep RNA sequencing on eight myofibroma samples, including two from patients with IMF. We identified five different in‐frame gene fusions in six patients, including three previously described fusion transcripts, SRF‐CITED1, SRF‐ICA1L and MTCH2‐FNBP4, and a fusion of unknown significance, FN1‐TIMP1. We found a novel COL4A1‐VEGFD gene fusion in two cases, one of which also carried a PDGFRB mutation. We observed a robust expression of VEGFD by immunofluorescence on the corresponding tumour sections. Finally, we showed that the COL4A1‐VEGFD chimeric protein was processed to mature VEGFD growth factor by proteases, such as the FURIN proprotein convertase. In conclusion, our results unravel a new recurrent gene fusion that leads to VEGFD production under the control of the COL4A1 gene promoter in myofibroma. This fusion is highly reminiscent of the COL1A1‐PDGFB oncogene associated with dermatofibrosarcoma protuberans. This work has implications for the diagnosis and, possibly, the treatment of a subset of myofibromas.

A Multicenter Phase II Study of Pazopanib in Patients with Unresectable Dermatofibrosarcoma Protuberans

Dermatofibrosarcoma protuberans (DFSP) is a soft-tissue sarcoma characterized by a high risk of local infiltration. The identification of the COL1A1-PDGFB t(17;22) translocation activating the PDGF pathway led to the use of imatinib in unresectable DFSP, with a response rate of 36-80%. Pazopanib is a multitarget tyrosine kinase inhibitor approved for soft-tissue sarcomas. We conducted a phase II study of patients with unresectable DFSP to evaluate the efficacy and safety of pazopanib. Patients received 800 mg of pazopanib daily. The primary endpoint was the objective response rate defined as the reduction of the largest diameter of the tumor by ≥30% at 6 months or at surgery. A total of 23 patients, including one pretreated with imatinib, were enrolled. With a median follow-up of 6.2 months (interquartile range = 5.6-7.8 months), five patients (22%, 95% confidence interval = 7-22%) had a partial response to pazopanib. The best objective response rate was 30% (95% confidence interval = 13-53%) using Response Evaluation Criteria in Solid Tumors. One patient with metastatic DFSP previously treated with imatinib died after 2.4 months. Nine patients (39%) discontinued the treatment owing to adverse events. Pharmacodynamics analyses of tumor samples were conducted: the enrichment of EGF and the EGFR-associated gene panel was associated with resistance, suggesting that EGFR-targeted therapies could be a therapeutic option to explore in DFSP. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01059656.

Establishment and characterization of NCC-DFSP3-C1: a novel patient-derived dermatofibrosarcoma protuberans cell line

Dermatofibrosarcoma protuberans (DFSP) is the most common dermal sarcoma; it is characterized by the presence of the COL1A1-PDGFB translocation, which causes the constitutive activation of the platelet-derived growth factor β (PDGFB) signaling pathway. DFSP frequently exhibits local recurrence and is refractory to conventional chemotherapy. Therefore, a novel therapeutic strategy is required for improving the prognosis of DFSP. Although patient-derived cell lines are important tools for pre-clinical studies, currently, only a few such cell lines are available for DFSP in cell banks. Here, we report the establishment of a novel DFSP cell line. Using a surgically resected metastatic tumor tissue from a patient with DFSP, we established a cell line called NCC-DFSP3-C1. The NCC-DFSP3-C1 cells had a COL1A1-PDGFB translocation and retained the same copy number aberrations as the original tumor tissue. NCC-DFSP3-C1 cells exhibited constant growth, spheroid formation, and invasive ability. By screening a drug library, we identified anti-cancer agents with inhibitory effects on the proliferation of NCC-DFSP3-C1 cells; these anti-cancer agents included proteasomal, histone deacetylase, and kinase inhibitors. We concluded that the NCC-DFSP3-C1 cell line may serve as a useful tool for performing basic and pre-clinical studies on DFSP.

Using biology to guide the treatment of sarcomas and aggressive connective-tissue tumours

Sarcomas are a heterogeneous group of malignancies that arise from cells of a mesenchymal origin. Surgery forms the mainstay of the treatment of most patients with localized sarcoma and might be followed or preceded by chemotherapy and/or radiotherapy. In the metastatic setting, systemic treatments tend to improve survival and control symptoms. However, the adverse events and sometimes disappointing outcomes associated with these empirical approaches to treatment indicate a need for new approaches. The advent of next-generation sequencing (NGS) has enabled more targeted treatment of many malignancies based on the presence of specific alterations. NGS analyses of sarcomas have revealed the presence of many alterations that can be targeted using therapies that are already used in patients with other forms of cancer. In this Review, we describe the genomic alterations considered to define specific nosological subgroups of sarcoma and whose contribution to oncogenesis provides a biological rationale for the use of a specific targeted therapy. We also report several less successful examples that should guide researchers and clinicians to better define the extent to which the identification of driver molecular alterations should influence the development of novel treatments.

Dermatofibrosarcoma protuberans: A rare and devastating tumor of the vulva

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Biopsies of a large mass are prone to sampling errors and may lead to an incorrect diagnosis.

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MRI imaging of vulvar tumors can aid in surgical planning.

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Large sarcomas of the vulva require a multi-disciplinary approach.

Establishment of novel patient-derived models of dermatofibrosarcoma protuberans: two cell lines, NCC-DFSP1-C1 and NCC-DFSP2-C1

Dermatofibrosarcoma protuberans (DFSP) is a common type of dermal sarcoma, characterized by the presence of the unique collagen type I alpha 1 chain (COL1A1)-PDGFB translocation, which causes constitutive activation of the platelet-derived growth factor β (PDGFB) signaling pathway. Patients with DFSP exhibit frequent local recurrence, and novel therapeutic approaches are required to achieve better clinical outcomes. Patient-derived cancer cell lines are essential in the preclinical research. Here, we established novel patient-derived DFSP cell lines from two patients with DFSP and designated these cell lines NCC-DFSP1-C1 and NCC-DFSP2-C1. Tumors of the two patients with DFSP had COL1A1-PDGFB translocations with distinct COL1A1 breakpoints, e.g., in exons 33 and 15, and the translocations were preserved in the established cell lines. NCC-DFSP1-C1 and NCC-DFSP2-C1 cells exhibited similar morphology and limited capability of proliferation in vitro, forming spheroids when seeded on low-attachment tissue culture plates. In contrast, NCC-DFSP1-C1 cells had considerably higher invasive capability than NCC-DFSP2-C1 cells. Overall proteome contents were similar between NCC-DFSP1-C1 and NCC-DFSP2-C1 cells. Notably, in vitro screening studies identified anticancer drugs that showed antiproliferative effects at considerably low concentrations in the DFSP cell lines. Bortezomib, mitoxantrone, ponatinib, and romidepsin were more cytotoxic to NCC-DFSP1-C1 cells than to NCC-DFSP2-C1 cells. These cell lines will be useful tools for developing novel therapeutic strategies to treat DFSP.

Alternative PDGFD rearrangements in dermatofibrosarcomas protuberans without PDGFB fusions

Dermatofibrosarcoma protuberans is underlined by recurrent collagen type I alpha 1 chain-platelet-derived growth factor B chain (COL1A1-PDGFB) fusions but ~ 4% of typical dermatofibrosarcoma protuberans remain negative for this translocation in routine molecular screening. We investigated a series of 21 cases not associated with the pathognomonic COL1A1-PDGFB fusion on routine fluorescence in situ hybridization (FISH) testing. All cases displayed morphological and clinical features consistent with the diagnosis of dermatofibrosarcoma protuberans. RNA-sequencing analysis was successful in 20 cases. The classical COL1A1-PDGFB fusion was present in 40% of cases (n = 8/20), and subsequently confirmed with a COL1A1 break-apart FISH probe in all but one case (n = 7/8). 55% of cases (n = 11/20) displayed novel PDGFD rearrangements; PDGFD being fused either to the 5' part of COL6A3 (2q37.3) (n = 9/11) or EMILIN2 (18p11) (n = 2/11). All rearrangements led to in-frame fusion transcripts and were confirmed at genomic level by FISH and/or array-comparative genomic hybridization. PDGFD-rearranged dermatofibrosarcoma protuberans presented clinical outcomes similar to typical dermatofibrosarcoma protuberans. Notably, the two EMILIN2-PDGFD cases displayed fibrosarcomatous transformation and homozygous deletions of CDKN2A at genomic level. We report the first recurrent molecular variant of dermatofibrosarcoma protuberans involving PDGFD, which functionally mimic bona fide COL1A1-PDGFB fusions, leading presumably to a similar autocrine loop-stimulating PDGFRB. This study also emphasizes that COL1A1-PDGFB fusions can be cytogenetically cryptic on FISH testing in a subset of cases, thereby representing a diagnostic pitfall that pathologists should be aware of.

Dermatofibrosarcoma protuberans with a novel COL6A3-PDGFD fusion gene and apparent predilection for breast

Dermatofibrosarcoma protuberans is a locally aggressive superficial mesenchymal neoplasm. It typically occurs in adulthood, and has been reported to have a slight male predilection. Tumors have a characteristic histopathologic appearance, including: storiform architecture, infiltrative "honeycomb" growth within subcutaneous adipose tissue, and immunoreactivity for CD34. Virtually all molecularly characterized cases to date have been found to harbor a COL1A1-PDGFB fusion product. Following identification of an index patient with a novel COL6A3-PDGFD fusion gene, we undertook a molecular investigation, using a combination of RNA sequencing and fluorescence in situ hybridization (FISH), to assess the prevalence of PDGFD rearrangement in dermatofibrosarcoma protuberans (N = 63). Three additional patients were found to have balanced PDGFD rearrangements. Interestingly, all 4 tumors arose on the breast of females. As a result, we subsequently examined 16 additional cases of primary breast dermatofibrosarcoma protuberans, identifying 2 additional tumors with PDGFD rearrangement. The morphology and immunophenotype of all 6 cases was analogous to those with the canonical COL1A1-PDGFB fusion; none of the cases showed fibrosarcomatous transformation. This study illustrates that the COL6A3-PDGFD fusion product is rare in dermatofibrosarcoma protuberans, and associated with an apparent predilection for breast. An awareness of this variant is important for pathologists, as it will not be detected using conventional reverse transcription polymerase chain reaction or FISH-based diagnostic assays for dermatofibrosarcoma protuberans.

Antitumor efficacy of the heparan sulfate mimic roneparstat (SST0001) against sarcoma models involves multi-target inhibition of receptor tyrosine kinases

The heparan sulfate (HS) mimic/heparanase inhibitor roneparstat (SST0001) shows antitumor activity in preclinical sarcoma models. We hypothesized that this 100% N-acetylated and glycol-split heparin could interfere with the functions of several receptor tyrosine kinases (RTK) coexpressed in sarcomas and activated by heparin-binding growth factors. Using a phospho-proteomic approach, we investigated the drug effects on RTK activation in human cell lines representative of different sarcoma subtypes. Inhibition of FGF, IGF, ERBB and PDGF receptors by the drug was biochemically and functionally validated. Roneparstat counteracted the autocrine loop induced by the COL1A1/PDGFB fusion oncogene, expressed in a human dermatofibrosarcoma protuberans primary culture and in NIH3T3^COL1A1/PDGFB transfectants, inhibiting cell anchorage-independent growth and invasion. In addition, roneparstat inhibited the activation of cell surface PDGFR and PDGFR-associated FAK, likely contributing to the reversion of NIH3T3^COL1A1/PDGFB cell transformed and pro-invasive phenotype. Biochemical and histological/immunohistochemical ex vivo analyses confirmed a reduced activation of ERBB4, EGFR, INSR, IGF1R, associated with apoptosis induction and angiogenesis inhibition in a drug-treated Ewing's sarcoma family tumor xenograft. The combination of roneparstat with irinotecan significantly improved the antitumor effect against A204 rhabdoid xenografts resulting in a high rate of complete responses and cures. These findings reveal that roneparstat exerts a multi-target inhibition of RTKs relevant in the pathobiology of different sarcoma subtypes. These effects, likely cooperating with heparanase inhibition, contribute to the antitumor efficacy of the drug. The study supports heparanase/HS axis targeting as a valuable approach in combination therapies of different sarcoma subtypes providing a preclinical rationale for clinical investigation.

Involvement of platelet-derived growth factor ligands and receptors in tumorigenesis

Platelet-derived growth factor (PDGF) isoforms and their receptors have important roles during embryogenesis, particularly in the development of various mesenchymal cell types in different organs. In the adult, PDGF stimulates wound healing and regulates tissue homeostasis. However, overactivity of PDGF signalling is associated with malignancies and other diseases characterized by excessive cell proliferation, such as fibrotic conditions and atherosclerosis. In certain tumours, genetic or epigenetic alterations of the genes for PDGF ligands and receptors drive tumour cell proliferation and survival. Examples include the rare skin tumour dermatofibrosarcoma protuberance, which is driven by autocrine PDGF stimulation due to translocation of a PDGF gene, and certain gastrointestinal stromal tumours and leukaemias, which are driven by constitute activation of PDGF receptors due to point mutations and formation of fusion proteins of the receptors, respectively. Moreover, PDGF stimulates cells in tumour stroma and promotes angiogenesis as well as the development of cancer-associated fibroblasts, both of which promote tumour progression. Inhibitors of PDGF signalling may thus be of clinical usefulness in the treatment of certain tumours.

Dermatofibrosarcoma Protuberans

OPINION STATEMENT

Dermatofibrosarcoma protuberans (DFSP) is a slow growing tumor with a very low metastatic potential but with significant subclinical extension and great capacity for local destruction. Thus, the first surgeon approached with such challenging tumor must attempt to cure the patient with a method that spares healthy tissue and ensures an optimal oncological, functional, and esthetic result. The treatment of DFSP often requires a multidisciplinary approach. Depending on location, dermatologic surgeons, surgical oncologists, head and neck surgeons, neurosurgeons, plastic surgeons, and occasionally medical oncologists may be involved with the management. Mohs micrographic surgery (MMS) is the preferred method when available. In our institution, most of the DFSP cases are often advanced cases; thus, dermatologic surgeons obtain clear margins peripherally and other surgical specialties assist with resection of the fascia and any critical deeper structures. When MMS is not available, wide local excision (at least 2- to 3-cm margins of resection) with exhaustive pathologic assessment of margin status is recommended, and it is best to confirm tumor extirpation prior to any reconstruction. Subclinical extension of the tumor could be related to the size; how long it has been growing or histological markers that are unknown right now. No clinical trials comparing MMS vs WLE are available, and further research should be focused on these subjects as well as the use of imatinib and other targeted therapies for recurrent and metastatic tumors and for neoadjuvant treatment.

Systemic treatment in advanced soft tissue sarcoma: what is standard, what is new

For metastatic soft tissue sarcoma (STS) patients not eligible for surgery, systemic treatments, including standard chemotherapy and newer biological compounds, still play the most relevant role in the management of the disease. An anthracycline and alkylating agent combination has formed the cornerstone of chemotherapy in STS for more than 30 years, with its value over that of administration of anthracycline as a single agent still being debated. Efforts have been made to improve the activity and minimise the toxicity of the combination, as well as to explore the upfront efficacy of agents known to be active in sarcoma and to develop new biological compounds. Nevertheless, beyond the first line, evidence for medical treatment in STS is less robust and all the more driven by histology. Thus, the introduction of kinases and small molecule inhibitors in the treatment armamentarium for STS is a major achievement in this setting. Preliminary data on immunotherapy are also available and discussed in this review.

Dermatofibrosarcoma Protuberans-Like Tumor With COL1A1 Copy Number Gain in the Absence of t(17;22)

A 57-year-old woman presented with a 3-year history of a progressive firm plaque on the right cheek. Skin biopsies revealed a bland, storiform, spindle-cell proliferation involving the deep dermis and subcutaneous fat. By immunohistochemistry, the tumor cells were diffusely positive for CD34 and caldesmon with multifocal reactivity for epithelial membrane antigen and focal, weak staining for smooth muscle actin. Retinoblastoma protein expression was not detectable in tumor cells by immunohistochemistry. An interphase fluorescence in situ hybridization analysis for platelet-derived growth factor B (PDGFB) gene rearrangement was negative. A single-nucleotide polymorphism array study detected 1) a gain of chromosome segment 17q21.33-q25.3 which overlapped the entire COL1A1 gene with a breakpoint at 17q21.33, approximately 250 Kb centromeric to the 3' end of COL1A1 gene, 2) several segmental gains on chromosome 11, and 3) an RB1 gene locus with normal copy number and allele frequency. Although the current case resembles dermatofibrosarcoma protuberans, it is unique in that it demonstrates a copy number gain of chromosome 17q in the absence of fusion of COL1A1 and PDGFB genes and an unusual immunohistochemical staining profile. The morphologic and molecular findings suggest a novel molecular variant of dermatofibrosarcoma protuberans not detectable with standard fluorescence in situ hybridization for PDGFB rearrangement. This variant appears to respond to imatinib after 9 months of follow-up.

Evolution of Dermatofibrosarcoma Protuberans to DFSP-Derived Fibrosarcoma: An Event Marked by Epithelial-Mesenchymal Transition-like Process and 22q Loss

Dermatofibrosarcoma protuberans (DFSP) is a rare and indolent cutaneous sarcoma. At times, a fibrosarcomatous transformation marked by a more aggressive clinical behavior may be present. We investigated the natural history and the molecular bases of progression from classic DFSP to the fibrosarcomatous form (FS-DFSP), looking, retrospectively, at the outcome of all patients affected by primary DFSP treated at our institution from 1993 to 2012 and analyzing the molecular profile of 5 DFSPs and 5 FS-DFSPs by an integrated genomics approach (whole transcriptome sequencing, copy number analysis, FISH, qRT-PCR, IHC). The presence of fibrosarcomatous features was identified in 20 (7.6%) patients out of 263 DFSP. All cases were treated with macroscopic complete surgery. A local relapse occurred in 4 of 23 patients who received a microscopic marginal surgery (2 classic DFSP, 2 FS-DFSP), while metastasis affected 2 patients, both FS-DFSP (10% of FS-DFSP), being the first event. DFSP evolution to FS-DFSP was paralleled by a transcriptional reprogramming. The recurrent loss of chromosome 22q appeared to contribute to this phenomenon by promoting the expression of epigenetic regulators, such as EZH2. Loss of the p16/CDKN2A/INK4A locus at 9p was also observed in two FS-DFSP metastatic cases.

IMPLICATIONS

FS-DFSP is a rare subgroup among DFSP, with a 10% metastatic risk, that was independent from local recurrence and that was not observed in DFSP, that were all cured by wide surgery. Chromosome 22q deletion might play a role in FS-DFSP, and p16 loss may convey a poor outcome. EZH2 dysregulation was also found and represents a druggable target. Mol Cancer Res; 14(9); 820-9. ©2016 AACR.

Dermatofibrosarcoma protuberans: from translocation to targeted therapy

Dermatofibrosarcoma protuberans (DFSP), the most common dermal sarcoma, is a low-grade, slow growing fibroblastic malignant neoplasm that most frequently affects middle aged adults and is characterized by a high local recurrence rate and a low propensity for metastasis. Wide surgical resection or Mohs micrographic surgery (MMS) are the preferred approaches for localized disease, while radiation therapy is warranted for inoperable disease or for cases with positive margins where re-excision is not possible. DFSP is generally regarded as refractory to conventional chemotherapy. Treatment options for systemic disease were limited until the discovery of a unique translocation, t(17;22)(q22;q13) (COL1A1;PDGFB) found in a majority of cases. In recent years, imatinib, a PDGFβR, ABL and KIT inhibitor, has revolutionized systemic therapy in DFSP. In this review, we summarize the epidemiological, clinical, histological and genetic characteristics of DFSP and update the readers on its current management.

MicroRNAs and Growth Factors: An Alliance Propelling Tumor Progression

Tumor progression requires cancer cell proliferation, migration, invasion, and attraction of blood and lymph vessels. These processes are tightly regulated by growth factors and their intracellular signaling pathways, which culminate in transcriptional programs. Hence, oncogenic mutations often capture growth factor signaling, and drugs able to intercept the underlying biochemical routes might retard cancer spread. Along with messenger RNAs, microRNAs play regulatory roles in growth factor signaling and in tumor progression. Because growth factors regulate abundance of certain microRNAs and the latter modulate the abundance of proteins necessary for growth factor signaling, the two classes of molecules form a dense web of interactions, which are dominated by a few recurring modules. We review specific examples of the alliance formed by growth factors and microRNAs and refer primarily to the epidermal growth factor (EGF) pathway. Clinical applications of the crosstalk between microRNAs and growth factors are described, including relevance to cancer therapy and to emergence of resistance to specific drugs.

Efficacy and Biological Activity of Imatinib in Metastatic Dermatofibrosarcoma Protuberans (DFSP)

PURPOSE

To report on imatinib mesylate (IM) in patients with metastatic dermatofibrosarcoma protuberans (DFSP)/fibrosarcomatous (FS)-DFSP and on the impact of the treatment on tumor biology.

EXPERIMENTAL DESIGN

Ten consecutive patients treated with IM from 2007 to 2015 for a metastatic relapse from DFSP/FS-DFSP were identified. FISH analysis for COL1A1-PDGFB was performed. Two IM-treated and 4 naïve FS-DFSP were transcriptionally profiled by RNAseq on HiScanSQ platform. Differential gene expression was analyzed with edgeR (Bioconductor), followed by hierarchical clustering and Principal Component Analysis.

RESULTS

All cases featured fibrosarcomatous in the metastasis and retained the COL1A1-PDGFB. Best RECIST response was: 8 partial response, 1 stable disease, and 1 progressive disease. Median progression-free survival was 11 months. Five patients received surgery after IM and all relapsed. IM was restored in 4 patients with a new response. After IM, the most upregulated genes included those encoding for immunoglobulins and those affecting functions and differentiation of endothelial cells. Pathway enrichment analysis revealed upregulation in genes involved in antigen processing and presentation, natural killer-mediated cytotoxicity, and drug and xenobiotics metabolism. Conversely, a significant down-regulation of kinase signaling pathways was detected.

CONCLUSIONS

All metastatic cases were fibrosarcomatous. Most patients responded to IM, but PFS was shorter than reported in published series which included both DFSP and FS-DFSP. All patients operated after IM had a relapse, suggesting that IM cannot eradicate metastatic cases and that the role of surgery is limited. Transcriptional profile of naïve and posttreatment samples pointed the contribution of immune infiltrates in sustaining the response to IM.

Current treatment options for dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is rare, infiltrating dermal neoplasm, characterized by indolent growth and low probability of metastases. The critical event in DFSP development is the rearrangement of chromosome 17 and 22, leading to transcriptional up-regulation of platelet-derived growth factor, providing an autocrine and/or paracrine stimulus. The cornerstone of treatment for localized DFSP is complete surgical resection with microscopically negative margins. Adjuvant radiotherapy is suggested in cases of positive margins when re-excision is not feasible. The first effective systemic therapy in DFSP introduced into clinical practice was imatinib, demonstrating dramatic activity in advanced cases. Current results indicate that some DFSP patient initially evaluated as unresectable/metastatic or necessitating mutilating surgery turned resectable after imatinib therapy and this rational approach leading to complete remission maybe potentially curative. The clinical experience with other tyrosine kinase inhibitors is limited and imatinib remains the gold standard treatment of locally unresectable/metastatic DFSP. This review summarizes state of the art and perspectives on the DFSP management.

Dermatofibrosarcoma protuberans: a study of clinical, pathologic, genetic, and therapeutic features in Korean patients

PURPOSE

Dermatofibrosarcoma protuberans (DFSP) carries a translocation resulting in the collagen type I alpha 1 (COL1A1)-platelet-derived growth factor beta (PDGFB) fusion gene, which is responsible for PDGFB activation. The purpose of this study is to evaluate the clinicopathological, genetic, and therapeutic features of DFSP in Korean patients.

MATERIALS AND METHODS

Clinicopathological features of 37 patients with DFSP were reviewed. Multiplex reverse transcriptase-polymerase chain reaction (PCR) was carried out in 16 patients using formalin-fixed, paraffin-embedded tissues and specific primers for COL1A1 and PDGFB.

RESULTS

The mean age of 37 patients was 37.4 years old. The most common tumor location was the trunk. All patients were treated primarily with surgery: 34 (91.7%) cases with Mohs micrographic surgery (MMS) and 3 (8.3%) cases with wide local excision. The median follow-up time was 33.7 months. Two patients, one in each treatment group, demonstrated local recurrence during the follow-up period. The COL1A1-PDGFB fusion gene was expressed in 14 (87.5%) cases, demonstrated by reverse transcriptase PCR analysis. No association was found among the different COL1A1-PDGFB fusion transcripts, the various histological subtypes and clinical features.

CONCLUSION

Our results support the effectiveness of MMS in treating DFSP. The COL1A1-PDGFB fusion transcript was observed in 87.5% of patients. Therefore, COL1A1-PDGFB is a useful and accurate tool in diagnosing DFSP in Koreans.

[Dermatofibrosarcoma protuberans: report of 38 cases]

Le dermatofibrosarcome protubérans de Darier et Ferrand est une tumeur cutanée rare. Le but de cette étude est de décrire les aspects épidémiologiques, cliniques, histologiques, thérapeutiques et évolutifs avec comparaison aux données de la littérature. Il s'agissait d'une étude rétrospective sur 10 ans à propos de 38 cas de dermatofibrosarcome de Darier et Ferrand pris en charge à l'Institut National d'Oncologie. Les données épidémiologiques, diagnostiques, thérapeutiques et évolutives ont été recueillies à partir des dossiers cliniques des patients et rapportées sur une fiche préétablie. L’âge médian des patients était de 41,5 ans. Tous les patients avaient une preuve histologique de dermatofibrosarcome. Seulement 30 patients ont été traités à l'Institut National d'Oncologie. L'exérèse chirurgicale de la tumeur était large, avec des marges de sécurité de 6-10 cm chez 6 patients (20%), 5 cm chez 16 patients (53%), 2-3 cm chez 4 patients (13%). En profondeur, l'exérèse emportait une barrière anatomique saine. 5 malades ont bénéficié d'une radiothérapie externe avec une dose médiane de 59,5 Gy. Le recul médian était de 64,4 mois (28- 138 mois). Le dermatofibrosarcome protubérans de Darier et Ferrand est une tumeur se distinguant par son évolution lente, son agressivité locale, son haut pouvoir de récidive et la rareté des métastases. Le traitement consiste en une exérèse large et profonde. Le pronostic dépend essentiellement de la qualité de l'exérèse initiale chirurgicale. La série étudiée présente des similitudes épidémiologiques, cliniques, et thérapeutiques avec les données de la littérature.

Platelet-derived growth factor signaling in human malignancies

Platelet-derived growth factors (PDGFs) and their receptors were identified and purified decades ago. PDGFs are important during normal development and in human cancers. In particular, autocrine PDGF signaling has been implicated in various types of malignancies such as gliomas and leukemia. In contrast, paracrine signaling was found in cancers that originate from epithelial cells, where it may be involved in stromal cell recruitment, metastasis, and epithelial-mesenchymal transition. This editorial briefly discusses autocrine and paracrine PDGF signaling and their roles in human cancers, and introduces a series of review articles in this issue that address the possible roles of PDGFs in various processes involved in different types of cancers.

Pediatric sarcomas: translating molecular pathogenesis of disease to novel therapeutic possibilities

Pediatric sarcomas represent a diverse group of rare bone and soft tissue malignancies. Although the molecular mechanisms that propel the development of these cancers are not well understood, identification of tumor-specific translocations in many sarcomas has provided significant insight into their tumorigenesis. Each fusion protein resulting from these chromosomal translocations is thought to act as a driving force in the tumor, either as an aberrant transcription factor (TF), constitutively active growth factor, or ligand-independent receptor tyrosine kinase. Identification of transcriptional targets or signaling pathways modulated by these oncogenic fusions has led to the discovery of potential therapeutic targets. Some of these targets have shown considerable promise in preclinical models and are currently being tested in clinical trials. This review summarizes the molecular pathology of a subset of pediatric sarcomas with tumor-associated translocations and how increased understanding at the molecular level is being translated to novel therapeutic advances.

Advances in molecular characterization and targeted therapy in dermatofibrosarcoma protuberans

The molecular pathogenesis of dermatofibrosarcoma protuberans (DFSP) involves distinctive rearrangement of chromosomes 17 and 22 leading to formation of the COL1A1-PDGFB fusion gene. The knowledge of molecular events underlying development of DFSP resulted in the implementation of targeted therapy with imatinib—a tyrosine kinase inhibitor (TKI), to the clinical practice. The striking efficacy of imatinib in advanced cases of DFSP has been demonstrated in a few clinical trials. Thus, imatinib is currently considered the gold standard in the treatment of inoperable and/or metastatic and/or recurrent cases of DFSP. Therapy with imatinib may potentially facilitate resection or decrease possible disfigurement related to radical surgical procedure. Following partial response on imatinib significant percentage of patients may be rendered free of the disease by surgery of the residual tumor.

Roles for growth factors in cancer progression

Under physiological conditions, cells receive fate-determining signals from their tissue surroundings, primarily in the form of polypeptide growth factors. Integration of these extracellular signals underlies tissue homeostasis. Although departure from homeostasis and tumor initiation are instigated by oncogenic mutations rather than by growth factors, the latter are the major regulators of all subsequent steps of tumor progression, namely clonal expansion, invasion across tissue barriers, angiogenesis, and colonization of distant niches. Here, we discuss the relevant growth factor families, their roles in tumor biology, as well as the respective downstream signaling pathways. Importantly, cancer-associated activating mutations that impinge on these pathways often relieve, in part, the reliance of tumors on growth factors. On the other hand, growth factors are frequently involved in evolvement of resistance to therapeutic regimens, which extends the roles for polypeptide factors to very late phases of tumor progression and offers opportunities for cancer therapy.

Imatinib mesylate in advanced dermatofibrosarcoma protuberans: pooled analysis of two phase II clinical trials

PURPOSE

Dermatofibrosarcoma protuberans (DFSP) is a dermal sarcoma typically carrying a translocation between chromosomes 17 and 22 that generates functional platelet-derived growth factor B (PDGFB).

PATIENTS AND METHODS

Two distinct phase II trials of imatinib (400 to 800 mg daily) in patients with locally advanced or metastatic DFSP were conducted and closed prematurely, one in Europe (European Organisation for Research and Treatment of Cancer [EORTC]) with 14-week progression-free rate as the primary end point and the other in North America (Southwest Oncology Group [SWOG]) with confirmed objective response rate as the primary end point. In the EORTC trial, confirmation of PDGFB rearrangement was required, and surgery was undertaken after 14 weeks if feasible. The SWOG study confirmed t(17;22) after enrollment.

RESULTS

Sixteen and eight patients were enrolled onto the EORTC and SWOG trials, respectively. Tumor size ranged from 1.2 to 49 cm. DFSP was located on head/neck, trunk, and limb in seven, 11, and six patients, respectively, and was classic, pigmented, and fibrosarcomatous DFSP in 13, one, and nine patients, respectively. Metastases were present in seven patients (lung involvement was present six patients). Eleven patients (4%) had partial response as best response, and four patients had progressive disease as best response. Median time to progression (TTP) was 1.7 years. Imatinib was stopped in 11 patients because of progression, one patient because of toxicity, and two patients after complete resection of disease. Median overall survival (OS) time has not been reached; 1-year OS rate was 87.5%.

CONCLUSION

Imatinib is active in DFSP harboring t(17;22) including fibrosarcomatous DFSP, with objective response rate approaching 50%. Response rates and TTP did not differ between patients taking 400 mg daily versus 400 mg twice a day.

PDGFB quantification is a useful tool in the diagnosis of dermatofibrosarcoma protuberans: a study of 10 cases

BACKGROUND

Genetic aberrations involving the platelet-derived growth factor-beta (PDGFB) gene and the collagen type 1 alpha1 (COL1A1) gene have been implicated in the pathogenesis of dermatofibrosarcoma protuberans (DFSP), a slow-growing and locally infiltrative dermal tumour.

AIM

To investigate the genetic rearrangements in 10 patients who presented with a clinical diagnosis of DFSP.

METHODS

Total RNA was obtained from frozen sections and sections embedded in paraffin wax, and used for direct sequencing of the cDNA produced from reverse transcription (RT) PCR. The expression of PDFGB mRNA in each of these cases was also examined.

RESULTS

Of the 10 samples examined, 9 had the COL1A1/PDGFB fusion transcript by DNA sequencing. The sequenced products showed that there was a fusion between the end of exons 6, 8, 29 (two cases), 38, 25 or 47 (three cases) and the start of exon 2 of the PDGFB gene. Quantitative RT-PCR identified all samples as having significantly higher expression of the PDGFB gene compared with normal skin or dermatofibroma.

CONCLUSIONS

Detection of the COL1A1/PDGFB fusion transcript may be important for the diagnosis of DFSP. Furthermore, relative PDGFB gene quantification by real-time PCR may also provide a good diagnostic tool when other methods fail to give conclusive results.

The role of chromosomal alterations in human cancer development

Cancer cells become unstable and compromised because several cancer-predisposing mutations affect genes that are responsible for maintaining the genomic instability. Several factors influence the formation of chromosomal rearrangements and consequently of fusion genes and their role in tumorigenesis. Studies over the past decades have revealed that recurring chromosome rearrangements leading to fusion genes have a biological and clinical impact not only on leukemias and lymphomas, but also on certain epithelial tumors. With the implementation of new and powerful cytogenetic and molecular techniques the identification of fusion genes in solid tumors is being facilitated. Overall, the study of chromosomal translocations have revealed several recurring themes, and reached important insights into the process of malignant transformation. However, the mechanisms behind these translocations remain unclear. A more thorough understanding of the mechanisms that cause translocations will be aided by continuing characterization of translocation breakpoints and by developing in vitro and in vivo model systems that can generate chromosome translocation.

Myxoid Dermatofibrosarcoma Protuberans: A Rare Variant Analyzed in a Series of 23 Cases

The myxoid variant of dermatofibrosarcoma protuberans (DFSPs) is uncommon. It often presents a diagnostic challenge and is important to recognize to prevent both undertreatment and overtreatment. To better characterize this unusual variant of DFSP, 23 myxoid DFSPs (DFSP with greater than 50% myxoid stroma) were retrieved from the authors' consult files. 13 patients were male and 10 were female (median age 40 years; range 9 months to 72 years of age). Tumor size ranged from 1.5 to 11 cm (median 2.8 cm). The most frequent sites were the extremities (9) and head and neck (7), followed by the trunk (4) and anogenital region (3). Grossly, the tumors were white/tan/gray to yellow, firm to gelatinous soft tissue masses. Histologically, tumor stroma ranged from 50 to 100% myxoid (median 80%). The majority of cases displayed an infiltrative sheet-like proliferation of bland spindle cells with palely eosinophilic cytoplasm and stellate nuclei without pleomorphism. The stroma was myxoid with prominent thin-walled vessels. All cases displayed honeycomb infiltration of fat and 16 cases showed cellular areas of more typical DFSP. Four tumors contained pigmented dendritic cells (Bednar variant), 1 showed areas of giant cell fibroblastoma and 1 showed progression to fibrosarcomatous DFSP. Mitoses ranged from 0 to 5 per 10 high power fields. 95% of cases (21 out of 22) were positive for CD34 and all cases were negative for S100 and muscle markers. Clinical follow-up in 8 cases, ranging from 3-21 years, (median follow-up 6 years), revealed local recurrence in 2 cases and no evidence of metastasis. All patients were free of disease following wide excision or excision followed by radiotherapy. In summary, these low-grade lesions are clinically similar to typical DFSP, but their unusual morphology is easily confused with a variety of other tumor types.

Dermatofibrosarcoma protuberans: recent clinical progress

BACKGROUND

Dermatofibrosarcoma protuberans (DFSP) is a rare cutaneous tumor of low malignant grade characterized by a pattern of slow, infiltrative growth and a marked tendency to recur locally after surgical excision. Wide surgical resection is generally accepted as optimal treatment for DFSP. However, despite optimal surgical management, distant metastases may develop in up to 5% of patients. More than 90% of DFSP are characterized by a reciprocal chromosomal translocation, t(17;22). This rearrangement leads to constitutive activation of the platelet-derived growth factor receptor (PDGFR) as a result of deregulated ligand expression, thus providing a rationale for targeted inhibition of PDGFR as a treatment strategy for patients with unresectable locally advanced or metastatic DFSP.

METHODS

This article reviews the current understanding of DFSP, with emphasis on molecular-level pathogenetic events and their implications for management, and evidence for the role of tyrosine kinase inhibition in improving the outcomes of patients with unresectable locally advanced or metastatic DFSP.

RESULTS

Surgery with wide margins remains the cornerstone in the management of DFSP. Recently, imatinib, a potent, selective inhibitor of the PDGFR alpha and PDGFR beta protein-tyrosine kinases, has been reported to induce complete or partial remissions in most patients treated for advanced DFSP.

CONCLUSIONS

Imatinib is approved for treatment of adult patients with unresectable, recurrent, and/or metastatic DFSP who are not eligible for surgery. Future investigations will determine whether imatinib can also be used in the neoadjuvant setting to reduce tumor volume, thereby allowing resection of very large DFSP that would otherwise not be resectable.

PDGF Receptors as Targets in Tumor Treatment

Signaling through platelet-derived growth factor (PDGF) receptors contributes to multiple tumor-associated processes. The recent introduction of clinically useful PDGF inhibitors have the last years validated PDGF receptors in malignant and stromal cells as relevant cancer drug targets. Mutational activation of PDGF receptor signaling in malignant cells has been described in some rare tumor types such as dermatofibrosarcoma protuberans, a subset of GISTs, and some hematologic malignancies. Furthermore, expression of PDGF receptors on pericytes is a common characteristic of solid tumors. The clinical efficacy of novel multikinase inhibitors, such as sunitinib and sorafenib, most likely involves targeting of PDGF receptor-dependent pericytes. Preclinical studies suggest that targeting of stromal PDGF receptors might also constitute a novel strategy to enhance tumor drug uptake. Finally, recent studies have implied both pro- and antimetastatic effects of PDGF receptors on malignant and stromal cells. The studies on the roles of PDGF receptors in cancer signaling are thus presently in a dynamic phase where collaborations between oncologists, pathologists, and tumor biologists are predicted to be highly productive.

Análisis del gen de fusión COL1A1-PDGFB en un caso de dermatofibrosarcoma protuberans con componente de fibrosarcoma

Dermatofibrosarcoma protuberans (DFSP) is an infrequent tumor of intermediate malignancy, with little tendency to develop metastases but with a high rate of local recurrence. Cytogenetically, DFSP is characterized by a reciprocal translocation, t(17;22)(q22;q13), which is a conditioning factor in the fusion of the collagen type I alpha I gene (COL1A1) in chromosome 17q with the platelet-derived growth factor beta chain gene (PDGFB) in chromosome 22q. The fusion of these genes is variable, involving one of the 51 exons of the COL1A1 gene and exon 2 of the PDGFB gene. We present the case of a 37-year-old woman with a tumor on the arm whose histology showed a neoplastic infiltration of the subcutaneous cellular tissue made up of fusiform cells with an elongated nucleus in a storiform pattern and other more pleomorphic cells in a herringbone pattern, compatible with DFSP with a fibrosarcoma component. The molecular biology study with RT-PCR analysis of paraffin-embedded material and later sequencing showed a new fusion of exon 19 of the COL1A1 gene and exon 2 of PDGFB, supporting a diagnosis of DFSP. A study of the COL1A1-PDGFB fusion products is useful in cases where histology and immunohistochemistry are insufficient for the differential diagnosis of DFSP versus other sarcomas. It also justifies the use of new avenues of treatment with tyrosine kinase inhibitors.

Analysis of gene mutations in four cases of dermatofibrosarcoma protuberans

Fusion of the collagen type I alpha 1 (COL1A1) gene with the platelet-derived growth factor B-chain (PDGFB) gene has been described in dermatofibrosarcoma protuberans (DFSP). Various exons of the COL1A1 gene have been shown to be involved in the fusion with exon 2 of the PDGFB gene. We examined the breakpoints of the COL1A1 gene using the tumour specimens from four patients with DFSP. The COL1A1-PDGFB fusion transcripts were detected from the cultured tumour cells by reverse transcriptase polymerase chain reaction. Sequence analysis revealed that the ends of exons 23, 25, 26 and 36 in the COL1A1 gene were fused with the start of exon 2 in the PDGFB. This study identified three novel COL1A1 breakpoints: exons 23, 26 and 36 of the COL1A1 gene. In one case, the tumour was composed of two areas that differed in cytological atypia, cellularity and mitotic activity, indicating the dedifferentiation of the tumour. In tumour cells from two different areas the same aberrant fusion transcripts were identified. These results suggest that the dedifferentiation of tumour cells has nothing to do with the specific breakpoints of the COL1A1 gene, but depends on other unknown factors.

Dermatofibrosarcoma protuberans: report of a case with a variant ring chromosome and metastases following pregnancy

BACKGROUND

The most frequent molecular abnormality observed in dermatofibrosarcoma protuberans (DFSP) is the formation of a supernumerary ring chromosome or translocation resulting in fusion of the gene encoding the alpha-chain of type 1 collagen, COL1A1 from 17q22, to the platelet-derived growth factor beta-chain, PDGFB gene from 22q13. Rare cases documenting variant ring or marker chromosomes involving regions other than 17q22 and 22q13 have been reported. Further analysis in three of these cases demonstrated the presence of the COL1A1 and PDGFB genes.

METHODS

We report a further case of DFSP with a rare variant ring chromosome. The tumor appeared to undergo accelerated growth during pregnancy, then metastasized following pregnancy. We describe the clinical, histological, immunohistochemical, and cytogenetic features.

RESULTS

The metastatic tumor showed a variant r(17;?) chromosome. A locus-specific probe was required to demonstrate presence of the PDGFB gene within the ring, indicating cryptic molecular rearrangement between chromosomes 17 and 22, and recombination with an unknown chromosome.

CONCLUSIONS

Cryptic rearrangement of chromosomes 17 and 22 should be suspected in variant ring chromosomes and translocations. Pregnancy may contribute to accelerated growth of DFSP, and delay in surgical resection should be avoided.

Gene mutation analysis in five cases of dermatofibrosarcoma protuberans using formalin-fixed, paraffin-embedded tissues

Fusion of the collagen type I a 1 (COL1A1) gene with the platelet-derived growth factor B-chain (PDGFB) gene has been pointed out in dermatofibrosarcoma protuberans. Various exons of the COL1A1 gene have been shown to be involved in the fusion with exon 2 of the PDGFB gene. We studied the breakpoints of the COL1A1 gene using formalin-fixed, paraffin-embedded tumour specimens from five patients with dermatofibrosarcoma protuberans (three reconfirmations and two new cases). Reverse transcriptase-PCR was performed using paraffin-embedded tissues. Nucleotide sequence analysis was carried out using the PCR products to identify the breakpoints. The COL1A1-PDGFB fusion transcripts were detected from the tumour specimens. Sequence analysis revealed that the ends of exons 18, 29, 38, 42 and 44 in the COL1A1 gene were fused with the start of exon 2 in the PDGFB. This study identified a novel COL1A1 breakpoint, namely, exon 44 of the COL1A1 gene. Detection of the aberrant fusion transcript using formalin-fixed, paraffin-embedded tumour specimens is useful as a diagnostic aid for dermatofibrosarcoma protuberans in cases where fresh or frozen samples of tumour tissue are not available.

Imatinib Mesylate (Gleevec)-Targeted Kinases Are Expressed in Uterine Sarcomas

The purpose of this study was to determine whether 3 tyrosine kinases known to be inhibited by imatinib mesylate are expressed in a variety of uterine sarcomas. The authors assessed c-kit, abl, and platelet-derived growth factor receptor-beta (PDGFR-beta) expression in 8 endometrial stromal sarcomas (ESSs), 5 leiomyosarcomas (LMSs), 4 high-grade endometrial sarcomas (HGESs), and 21 malignant mixed mullerian tumors (MMMTs). Tissue sections were stained with commercially available antibodies for c-kit, abl, and PDGFR-beta. Staining intensity was described as 0 (no staining), +1 (weak), +2 (moderate), and +3 (strong). Positive staining was defined as moderate to strong if found in more than 10% of tumor cells. Expression of c-kit ranged from 0% in LMSs to 25% in HGESs. Protein expression of abl was more significant, ranging from 25% in LMSs and ESSs to 43% in MMMTs. Only 1 LMS sample stained focally for abl (+1). Abl expression was observed in only the carcinomatous elements of the MMMTs, with diffuse staining in the cytoplasm and nucleus. In most, the staining intensity was +2. All tumors stained positive for PDGFR-beta. MMMT samples showed PDGFR-beta expression in both the carcinomatous and sarcomatous portions. In all samples, staining for PDGFR-beta was concentrated at the cell membrane and diffusely in the cytoplasm. These results indicate that many uterine sarcomas express 1 or more of the kinases targeted by imatinib mesylate and that further investigation of imatinib as a therapy for uterine sarcomas is warranted.

PDGF receptors-mediators of autocrine tumor growth and regulators of tumor vasculature and stroma

PDGFs and their cognate tyrosine kinase alpha- and beta-receptors are involved in multiple tumor-associated processes including autocrine growth stimulation of tumor cells, stimulation of tumor angiogenesis and recruitment and regulation of tumor fibroblasts. The recent development of clinically useful PDGF antagonists, like STI571/Glivec, has increased the interest in PDGF receptors as cancer drug targets. Autocrine PDGF receptor signaling occurs in certain malignancies characterized by mutational activation of PDGF or PDGF receptors, for instance, dermatofibrosaracoma protuberans, gastrointestinal stromal tumors, and hypereosinophilic syndrome. The roles of PDGF in regulation of tumor angiogenesis and tumor fibroblasts are more general, and probably occur in most common solid tumors. Concerning tumor angiogenesis recent studies have predominantly focused on the importance of PDGF receptor signaling for tumor pericyte recruitment. PDGF receptors in the tumor stroma have also attracted attention as interesting drug targets because of their function as regulators of tumor interstitial fluid pressure, tumor transvascular transport and tumor drug uptake. In summary, the improved understanding of the role of PDGF signaling in tumor biology, and the introduction of PDGF antagonists, has set the stage for a continued development of PDGF antagonists as novel cancer drugs.

Multiple epithelial and nonepithelial tumors in hereditary nonpolyposis colorectal cancer: characterization of germline and somatic mutations of the MSH2 gene and heterogeneity of replication error phenotypes

Hereditary nonpolyposis colorectal cancer (HNPCC) is an autosomal inherited cancer syndrome characterized by germline plus somatic mutations of DNA mismatch repair genes and familial clustering of cancers of colorectum and other visceral organs. So far, to our knowledge, there has been no proof of nonepithelial tumors in association with HNPCC. Here we report on a MSH2 frameshift HNPCC family with a carrier found to have multiple primary tumors, including endometrial hyperplasia, ovarian adenocarcinoma, skin cavernous hemangioma, and skin dermatofibrosarcoma protuberans (DFSP). We studied the replication error (RER) phenotype in noncoding (Bat-26, Bat-25, D2S123, D5S346, and D17S250) and coding (MSH3, MSH6, BAX, and TGFBR2 genes) DNA sequences, and characterized the germline and somatic mutations of the MSH2 gene in the tumors described above and in endometrial carcinomas from two of her affected siblings. RER was observed in an order of hyperplasic endometrium (6/10 markers), ovarian carcinoma (5/10 markers), endometrial carcinomas (4/9 and 3/10), DFSP (2/9 markers), and cavernous hemangioma (2/10 markers). All the tumors showed the same germline mutation of G5-->G6 frameshift at 183-187 and polymorphism of C1168T in a heterozygous pattern. In an endometrial carcinoma, deletion of the second allele of MSH2 was evident. Heterogeneous RER patterns were noted in multiple primary tumors of the same individual and in premalignant and malignant endometrial tumors from different individuals. The study demonstrated the two hits of the hMSH(2) gene as well as intra- and interindividual variations of RER phenotypes in HNPCC. The first characterized nonepithelial tumors in HNPCC seem to carry a limited panel of RER, including a framesift at the (A)(10) tract of TGFBR2.

Apo D in soft tissue tumors: a novel marker for dermatofibrosarcoma protuberans

Using gene microarray expression profiling, we previously found that apolipoprotein D (Apo D) was highly expressed in dermatofibrosarcoma protuberans (DFSP). In this study, we confirm that Apo D is highly and relatively specifically expressed in DFSP using immunohistochemistry. A tissue microarray containing 421 soft tissue tumors was constructed and stained with antibodies against Apo D and CD34. Cytoplasmic immunostaining for Apo D was found in 9 of 10 typical DFSPs. In addition, 3 of 3 Bednar tumors and 2 of 3 giant cell fibroblastomas stained in conventional sections. In contrast, Apo D was immunoreactive in only a very small subset of a diverse collection of other soft tissue tumors, including Malignant Fibrous Histiocytoma (MFH), glomus tumor, neurofibroma, and malignant peripheral nerve sheath tumors. Immunostains for Apo D were negative in conventional sections of 16 fibrous histiocytomas, and an additional 12 variants of fibrous histiocytoma. Digital images of all immunohistochemical and hematoxylin and eosin tissue microarray stains are available at the accompanying website (http://microarray-pubs.stanford.edu/tma_portal/apod/). We conclude that Apo D is strongly expressed in DFSPs and neural lesions and may be useful in differentiating DFSP from fibrous histiocytoma.

Platelet-derived growth factor production by B16 melanoma cells leads to increased pericyte abundance in tumors and an associated increase in tumor growth rate

Platelet-derived growth factor (PDGF) receptor signaling participates in different processes in solid tumors, including autocrine stimulation of tumor cell growth, recruitment of tumor stroma fibroblasts, and stimulation of tumor angiogenesis. In the present study, the B16 mouse melanoma tumor model was used to investigate the functional consequences of paracrine PDGF stimulation of host-derived cells. Production of PDGF-BB or PDGF-DD by tumor cells was associated with an increased tumor growth rate. Characterization of tumors revealed an increase in pericyte abundance in tumors derived from B16 cells producing PDGF-BB or PDGF-DD. The increased tumor growth rate associated with PDGF-DD production was not seen in mice expressing an attenuated PDGF beta-receptor and was thus dependent on host PDGF beta-receptor signaling. The increased pericyte abundance was not associated with an increased tumor vessel density. However, tumor cell apoptosis, but not proliferation, was reduced in tumors displaying PDGF-induced increased pericyte coverage. Our findings thus demonstrate that paracrine PDGF production stimulates pericyte recruitment to tumor vessels and suggest that pericyte abundance influences tumor cell apoptosis and tumor growth.

Cutaneous and Subcutaneous Fibrohistiocytic Tumors of Intermediate Malignancy

The fibrohistiocytic tumors of intermediate malignancy are uncommon mesenchymal tumors, which typically occur in the skin and subcutis and which may pose significant problems for the dermatopathologist. This article reviews the clinical, histopathologic, and genetic features of dermatofibrosarcoma protuberans, giant cell fibroblastoma, angiomatoid (malignant) fibrous histiocytoma, plexiform fibrous histiocytoma, and soft tissue giant cell tumor (of low malignant potential). The differential diagnosis of these tumors with a variety of benign and fully malignant cutaneous soft tissue neoplasms is discussed.