Does the tuberous sclerosis complex include clivus chordoma? A case report

Emerging target discovery and drug repurposing opportunities in chordoma

The development of effective and personalized treatment options for patients with rare cancers like chordoma is hampered by numerous challenges. Biomarker-guided repurposing of therapies approved in other indications remains the fastest path to redefining the treatment paradigm, but chordoma's low mutation burden limits the impact of genomics in target discovery and precision oncology efforts. As our knowledge of oncogenic mechanisms across various malignancies has matured, it's become increasingly clear that numerous properties of tumors transcend their genomes - leading to new and uncharted frontiers of therapeutic opportunity. In this review, we discuss how the implementation of cutting-edge tools and approaches is opening new windows into chordoma's vulnerabilities. We also note how a convergence of emerging observations in chordoma and other cancers is leading to the identification and evaluation of new therapeutic hypotheses for this rare cancer.

Pediatric chordoma associated with tuberous sclerosis complex: A rare case report with a thorough analysis of potential therapeutic molecular targets

Chordoma associated with tuberous sclerosis complex (TSC) is an extremely rare tumor that was described only in 13 cases since 1975. Сhordoma itself is a malignant slow-growing bone tumor thought to arise from vestigial or ectopic notochordal tissue. Chordoma associated with TSC differs from chordoma in the general pediatric population in the median age, where the diagnosis of TSC-associated chordoma is 6.2 months, whereas for chordoma in the general pediatric population it is set to 12 years. The majority of TSC-associated chordomas are localized in skull-based and sacrum regions, and rare in the spine. Chordomas are genetically heterogeneous tumors characterized by chromosomal instability (CIN), and alterations involving PI3K-AKT signaling pathway genes and chromatin remodeling genes. Here we present the 14th case of chordoma associated with TSC in a 1-year-old pediatric patient. Alongside biallelic inactivation of the TSC1 gene, molecular genetic analysis revealed CIN and involvement of epigenetic regulation genes. In addition, we found the engagement of CBX7 and apolipoprotein B editing complex (APOBEC3) genes that were not yet seen in chordomas before. Amplification of CBX7 may epigenetically silence the CDKN2A gene, whereas amplification of APOBEC3 genes can explain the frequent occurrence of CIN in chordomas. We also found that KRAS gene is located in the region with gain status, which may suggest the ineffectiveness of potential EGFR monotherapy. Thus, molecular genetic analysis carried out in this study broadens the horizons of possible approaches for targeted therapies with potential applications for personalized medicine.

A novel TSC1 variant associated with tuberous sclerosis and sacrococcygeal teratoma

Tuberous sclerosis complex (TSC) is an autosomal dominant disease associated with tumors and malformed tissues in the brain and other vital organs. We report a novel de novo frameshift variant of the TSC1 gene (c.434dup;p. Ser146Valfs*8) in a child with TSC who initially presented with a sacral teratoma. This previously unreported association between TSC and teratoma has broad implications for the pathophysiology of embryonic tumors and mechanisms underlying cellular differentiation.

Chordoma Occurs in Young Children With Tuberous Sclerosis

Chordomas are rare bony neoplasms usually unassociated with a familial tumor predisposition syndrome. The peak incidence of this midline axial skeletal tumor is in adulthood but when very young children are affected, consideration should be given to occurrence within the tuberous sclerosis (TS) complex, especially when presenting in neonates <3 months of age. To call attention to this association, we present a brachyury-immunopositive chordoma occurring in the skull base of a 2-month-old male infant who was later realized to have metastases to the subcutaneous tissues and lungs, as well as rhabdomyoma of the heart and renal cysts/angiomyolipomas, that is, characteristic features of the TS complex. We review the limited literature on this topic.

Medical treatment of advanced chordomas

Chordoma is a very rare bone sarcoma that can arise from any site along the spine and from the skull base. En bloc resection is the gold standard for treatment while radiation therapy has been shown to provide both curative and palliative benefit. Unfortunately, local recurrences are common, even after a complete surgical resection, and up to 40% of patients suffer from distant metastases, while salvage treatments are challenging. Patients carrying an advanced disease need a systemic treatment. Unluckily, conventional chordoma are insensitive to cytotoxic chemotherapy that is considered the standard treatment option in patients with metastatic sarcoma. In the last decade, innovative therapies have been introduced, positively impacting disease control and patients' quality of life. In addition, a better understanding of the molecular characteristics of chordoma allowed to detect new potential targets. This review is focused on the pharmacological management of patients affected by an advanced disease, starting with a summary of data available on conventional chemotherapy, then moving to a deeper analysis of available data on molecular agents and immunotherapy, and finally providing an update on ongoing clinical trials and future prospective.

Notochordal Tumors: An Update on Molecular Pathology with Therapeutic Implications

Recent molecular investigations of chordoma show common expression of various receptor tyrosine kinases and activation of downstream signaling pathways contributing to tumor growth and progression. The transcription factor brachyury (also known as T) is important in notochord differentiation, and germline duplication of the gene is often found in familial chordomas. Nuclear expression of brachyury is consistent in chordoma and in benign notochordal cell tumor. Based on the molecular evidence, targeting of several kinds of molecular agents has been attempted for the treatment of uncontrolled chordomas and achieved partial response or stable condition in many cases.

STAT3 Inhibition as a Therapeutic Strategy for Chordoma

Objective Signal transducer and activator of transcription (STAT) proteins regulate key cellular fate decisions including proliferation and apoptosis. STAT3 overexpression induces tumor growth in multiple neoplasms. STAT3 is constitutively activated in chordoma, a tumor with a high recurrence rate despite maximal surgical and radiation treatment. We hypothesized that a novel small molecule inhibitor of STAT3 (FLLL32) would induce significant cytotoxicity in sacral and clival chordoma cells. Methods Sacral (UCh1) and clival (UM-CHOR-1) chordoma cell lines were grown in culture (the latter derived from primary tumor explants). FLLL32 dosing parameters were optimized using cell viability assays. Antitumor potential of FLLL32 was assessed using clonal proliferation assays. Potential mechanisms underlying observed cytotoxicity were examined using immunofluorescence assays. Results FLLL32 induced significant cytotoxicity in UCh1 and UM-CHOR-1 chordoma cells, essentially eliminating all viable cells, correlating with observed downregulation in activated, phosphorylated STAT3 upon administration of FLLL32. Mechanisms underlying the observed cytotoxicity included increased apoptosis and reduced cellular proliferation through inhibition of mitosis. Conclusion As a monotherapy, FLLL32 induces potent tumor kill in vitro in chordoma cell lines derived from skull base and sacrum. This effect is mediated through inhibition of STAT3 phosphorylation, increased susceptibility to apoptosis, and suppression of cell proliferation.

Chordoma: the entity

Chordomas are malignant tumors of the axial skeleton, characterized by their locally invasive and slow but aggressive growth. These neoplasms are presumed to be derived from notochordal remnants with a molecular alteration preceding their malignant transformation. As these tumors are most frequently observed on the skull base and sacrum, patients suffering from a chordoma present with debilitating neurological disease, and have an overall 5-year survival rate of 65%. Surgical resection with adjuvant radiotherapy is the first-choice treatment modality in these patients, since chordomas are resistant to conventional chemotherapy. Even so, management of chordomas can be challenging, as chordoma patients often present with recurrent disease. Recent advances in the understanding of the molecular events that contribute to the development of chordomas are promising; the most novel finding being the identification of brachyury in the disease process. Here we present an overview of the current paradigms and summarize relevant research findings.

Chemotherapy of skull base chordoma tailored on responsiveness of patient-derived tumor cells to rapamycin

Skull base chordomas are challenging tumors due to their deep surgical location and resistance to conventional radiotherapy. Chemotherapy plays a marginal role in the treatment of chordoma resulting from lack of preclinical models due to the difficulty in establishing tumor cell lines and valuable in vivo models. Here, we established a cell line from a recurrent clival chordoma. Cells were cultured for more than 30 passages and the expression of the chordoma cell marker brachyury was monitored using both immunohistochemistry and Western blot. Sensitivity of chordoma cells to the inhibition of specific signaling pathways was assessed through testing of a commercially available small molecule kinase inhibitor library. In vivo tumorigenicity was evaluated by grafting chordoma cells onto immunocompromised mice and established tumor xenografts were treated with rapamycin. Rapamycin was administered to the donor patient and its efficacy was assessed on follow-up neuroimaging. Chordoma cells maintained brachyury expression at late passages and generated xenografts closely mimicking the histology and phenotype of the parental tumor. Rapamycin was identified as an inhibitor of chordoma cell proliferation. Molecular analyses on tumor cells showed activation of the mammalian target of rapamycin signaling pathway and mutation of KRAS gene. Rapamycin was also effective in reducing the growth of chordoma xenografts. On the basis of these results, our patient received rapamycin therapy with about six-fold reduction of the tumor growth rate upon 10-month follow-up neuroimaging. This is the first case of chordoma in whom chemotherapy was tailored on the basis of the sensitivity of patient-derived tumor cells.

Generation of a patient-derived chordoma xenograft and characterization of the phosphoproteome in a recurrent chordoma

OBJECT

The management of patients with locally recurrent or metastatic chordoma is a challenge. Preclinical disease models would greatly accelerate the development of novel therapeutic options for chordoma. The authors sought to establish and characterize a primary xenograft model for chordoma that faithfully recapitulates the molecular features of human chordoma.

METHODS

Chordoma tissue from a recurrent clival tumor was obtained at the time of surgery and implanted subcutaneously into NOD-SCID interleukin-2 receptor gamma (IL-2Rγ) null (NSG) mouse hosts. Successful xenografts were established and passaged in the NSG mice. The recurrent chordoma and the derived human chordoma xenograft were compared by histology, immunohistochemistry, and phospho-specific immunohistochemistry. Based on these results, mice harboring subcutaneous chordoma xenografts were treated with the mTOR inhibitor MLN0128, and tumors were subjected to phosphoproteome profiling using Luminex technology and immunohistochemistry.

RESULTS

SF8894 is a novel chordoma xenograft established from a recurrent clival chordoma that faithfully recapitulates the histopathological, immunohistological, and phosphoproteomic features of the human tumor. The PI3K/Akt/mTOR pathway was activated, as evidenced by diffuse immunopositivity for phospho-epitopes, in the recurrent chordoma and in the established xenograft. Treatment of mice harboring chordoma xenografts with MLN0128 resulted in decreased activity of the PI3K/Akt/mTOR signaling pathway as indicated by decreased phospho-mTOR levels (p = 0.019, n = 3 tumors per group).

CONCLUSIONS

The authors report the establishment of SF8894, a recurrent clival chordoma xenograft that mimics many of the features of the original tumor and that should be a useful preclinical model for recurrent chordoma.

Incidence and relative survival of chordomas: the standardized mortality ratio and the impact of chordomas on a population

BACKGROUND

Chordomas are rare bone tumors arising from remnants of the embryonic notochord.

METHODS

Data for this study were obtained from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute (1973-2009) to calculate the incidence, relative survival (RS), and standardized mortality ratio (SMR) of patients diagnosed with intracranial and extracranial chordomas and to assess the effects of age and sex on this disease.

RESULTS

The overall incidence of extracranial and intracranial chordomas was 8.4 per 10 million population. The median overall survival of patients with chordoma patients was 7.7 years. The median survival was 7.7 years for male patients and 7.8 years for female patients. Younger patients (aged <40 years) survived longer compared with older patients (10-year RS, 68% vs 43%). The estimated age-standardized 5-year, 10-year, and 20-year RS rates was 72%, 48%, and 31%, respectively. The SMR in the overall cohort was 4.6 (95% confidence interval, 4.22-5.0) or 21.0 (95% confidence interval, 16.6-27.2) in young adult patients and 3.0 (95% confidence interval, 2.6-3.4) in elderly patients.

CONCLUSIONS

The elderly had a more aggressive form of this disease; and, other than the incidence, sex did not influence outcome in this disease. The study of chordomas presents a good case for the contribution that the SMR can have on measuring the impact of a disease on a population of patients. Although the younger population has better survival rates, the impact (SMR) in the younger age groups is much higher than in older populations.

Extraskeletal cartilaginous, osseous, and chordoid tumors in children and adolescents

Extraskeletal cartilaginous, osseous, and chordoid tumors are extraordinarily rare in children and adolescents. These lesions are diagnostically challenging due to their rarity and their overlap with metastatic osteosarcoma, reactive or metabolic calcifying and bone-forming masses, various pseudosarcomatous proliferations such as myositis ossificans, and other rare genetic or metabolic disorders. This article reviews the clinicopathologic features and differential diagnosis of extraskeletal cartilaginous, osseous, and chordoid neoplasms in the first two decades of life and highlights the use of diagnostic adjuncts.

Systemic therapy options for unresectable and metastatic chordomas

Chordoma is an exceedingly rare tumor, marked by a slow growth rate. Surgery is the treatment of choice, but the most frequent sites of origin (spine and skull base) make treatment of primary disease challenging. Local relapses affect more than 50% of cases, with a minority of patients being cured by further surgery. Furthermore, metastases occur in at least 20% of patients. For residual or recurrent disease, high-dose radiation therapy may be indicated. Radiation therapy is currently the preferred local treatment when surgery is problematic, exploiting most recent techniques, including proton beams and carbon ions. However, systemic therapy is needed in patients non-amenable to surgery and/or radiation therapy. We reviewed systemic treatments currently available, and targets possibly druggable in the future in this orphan disease.

Clinical features distinguish childhood chordoma associated with tuberous sclerosis complex (TSC) from chordoma in the general paediatric population

BACKGROUND

Chordoma, an age-dependent rare cancer, arises from notochordal remnants. Fewer than 5% of chordomas occur in children. Tuberous sclerosis complex (TSC) is an autosomal dominant neurocutaneous syndrome characterised by abnormal tissue growths in multiple organ systems. Reports of chordoma in children with TSC suggest that TSC1 and TSC2 mutations may contribute to chordoma aetiology.

METHODS

To determine whether the 10 TSC-associated childhood chordomas reported in the literature are representative of chordoma in the general paediatric population, the authors compared age at diagnosis, primary site and outcome in them with results from a systematic assessment of 65 paediatric chordoma cases reported to the US population-based cancer registries contributing to the SEER Program of the National Cancer Institute.

RESULTS

TSC-associated paediatric chordomas differed from chordomas in the general paediatric population: median age at diagnosis (6.2 months, TSC, vs 12.5 years, SEER); anatomical site (40% sacral, TSC, vs 9.4% sacral, SEER); and site-specific age at diagnosis (all four sacral chordomas diagnosed during the fetal or neonatal period, TSC, vs all six sacral chordomas diagnosed at >15 years, SEER). Finally, three of four patients with TSC-associated sacral chordoma were alive and tumour-free at 2.2, 8 and 19 years after diagnosis versus a median survival of 36 months among paediatric patients with sacral chordoma in SEER.

CONCLUSIONS

These results strengthen the association between paediatric chordoma and TSC. Future clinical and molecular studies documenting the magnitude and clinical spectrum of the joint occurrence of these two diseases should provide the basis for delineating the biological relationship between them.

The next step: innovative molecular targeted therapies for treatment of intracranial chordoma patients

BACKGROUND

Chordomas are rare, locally aggressive malignancies that often exhibit an insidious natural history and are difficult to eradicate. Surgery and radiotherapy are the treatment mainstays of chordoma, but the chance of local recurrence remains high. Patients who relapse or cannot undergo a complete en bloc resection generally have a poor prognosis. New agents for postoperative adjuvant treatment of chordomas are needed.

OBJECTIVE

To highlight potential clinical trials that could evolve from new insights into the molecular biology of chordoma.

METHODS

We performed a review of recent studies published in the literature that have begun to characterize the molecular features of chordoma, and with this knowledge, several targets for potential clinical therapies have been determined.

RESULTS

Several receptor tyrosine kinases and their downstream signaling cascades show dysregulation in chordoma and represent attractive targets for future therapeutic interventions. The pathways shown to be of particular importance in chordoma involve the platelet-derived growth factor receptor, epidermal growth factor receptor, hepatocyte growth factor receptor, and common downstream cascade of phosphoinositide 3-kinases, Akt, and mammalian target of rapamycin.

CONCLUSION

Recent findings characterizing the molecular biology of chordoma have illuminated multiple possible targets for future clinical trials. The availability of inhibitors against these aberrant pathways makes clinical trials with chordoma both feasible and immediately realizable. Additionally, we emphasize the rationale for combination therapy when implementing molecular therapy in chordoma and other cancers.

The biological basis for modern treatment of chordoma

Chordomas are rare malignant tumors arising in bone of the spheno-occiput, sacrum, and vertebral column which can cause neurological deficit. Current management of chordoma involves safe resection followed by radiation therapy. However, surgical resection is often subtotal and chordoma often recurs despite optimal therapy. Despite years of effort, effective adjuvant therapy for denovo, recurrent and metastatic chordoma are absent and 5-year survival is at best 65%. While no chemotherapeutic agent has been demonstrated to be effective against chordoma in vivo, a greater understanding of the genetics and molecular biology of chordoma is opening up avenues of investigation towards the rational development of targeted therapies. Although enthusiasm for the use of already established or new investigational agents will increase with greater understanding of chordoma biology, laboratory studies of these agents are important prior to incorporation into clinical human trials. The authors review the current state of knowledge regarding chordoma and offer insight into potential new therapies for this rare and challenging tumor.

Chordoma in the lateral medullary cistern in a patient with tuberous sclerosis: A case report and review of the literature

Background:

Chordomas are rare intracranial tumors. There are several reported cases of these tumors arising in patients with tuberous sclerosis (TSC), a neurocutaneous disorder inherited in autosomal dominant fashion that predisposes patients to hamartomatous and neoplastic lesions.

Case Description:

A 38-year-old man with the diagnosis of TSC presented with the complaint of dizziness and near syncope. Imaging revealed a mass in the lateral medullary cistern that was found at the time of surgery to be a chordoma. The patient underwent a left far lateral approach for removal of the tumor. Upon opening of the dura, the tumor could be seen under the arachnoid. The tumor was carefully debulked within the limits of safety. The patient did well postoperatively and was referred to the radiation oncology department at our institution for follow-up radiotherapy of the tumor bed.

Conclusion:

This study presents an unusual presentation and location for a chordoma and contributes to the growing literature associating chordomas with TSC.

Analysis of receptor tyrosine kinases (RTKs) and downstream pathways in chordomas

We have previously demonstrated that chordomas express activated platelet-derived growth factor receptor (PDGFRB) and that treatment with imatinib, which is capable of switching off the activation of various receptor tyrosine kinases (RTKs) including PDGFRB, benefits a number of patients. The aim of this study was to identify the possible presence of other activated RTKs and their downstream signaling effectors. Cryopreserved material from 22 naïve sporadic chordomas was investigated for the presence of activated RTKs and their cognate ligands and downstream signaling effectors by means of human phospho-RTK antibody arrays, Western blotting, and molecular analysis; immunohistochemistry and fluorescence in situ hybridization were used to analyze the corresponding formalin-fixed and paraffin-embedded samples. We detected activated PDGFRB, FLT3, and colony stimulating factor 1 receptor (CSF1R) of the PDGFR family and highly phosphorylated EGFR, HER2/neu, and (to a lesser extent) HER4 of the EGFR family. The detection of PDGFRB/PDGFB confirmed our previous data. The presence of activated EGFR was paralleled by the finding of high levels of epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha) and PDGFB co-expression and PDGFRB co-immunoprecipitation. Of the downstream effectors, the PI3K/AKT and RAS/MAPK pathways were both activated, thus leading to the phosphorylation of mammalian target of rapamycin (mTOR) and 4E-BP1 among the regulators involved in translational control. Taken together, our results (i) provide a rationale for tailored treatments targeting upstream activated receptors, including the PDGFR and EGFR families; (ii) support the idea that a combination of upstream antagonists and mTOR inhibitors enhances the control of tumor growth; and (iii) indicate that the 4E-BP1/eIF4E pathway is a major regulator of protein synthesis in chordoma.

Aberrant hyperactivation of akt and Mammalian target of rapamycin complex 1 signaling in sporadic chordomas

PURPOSE

Chordomas are rare, malignant bone neoplasms in which the pathogenic mechanisms remain unknown. Interestingly, tuberous sclerosis complex (TSC) is the only syndrome in which the incidence of chordomas has been described. We previously reported the pathogenic role of the TSC genes in TSC-associated chordomas. In this study, we investigated whether aberrant TSC/mammalian target of rapamycin complex 1 (mTORC1) signaling pathway is associated with sporadic chordomas.

EXPERIMENTAL DESIGN

We assessed the status of mTORC1 signaling in primary tumors/cell lines of sacral chordomas and further examined upstream of mTORC1 signaling, including the PTEN (phosphatase and tensin homologue deleted on chromosome ten) tumor suppressor. We also tested the efficacy of the mTOR inhibitor rapamycin on signaling and growth of chordoma cell lines.

RESULTS

Sporadic sacral chordoma tumors and cell lines examined commonly displayed hyperactivated Akt and mTORC1 signaling. Strikingly, expression of PTEN, a negative regulator of mTORC1 signaling, was not detected or significantly reduced in chordoma-derived cell lines and primary tumors. Furthermore, rapamycin inhibited mTORC1 activation and suppressed proliferation of chordoma-derived cell line.

CONCLUSIONS

Our results suggest that loss of PTEN as well as other genetic alterations that result in constitutive activation of Akt/mTORC1 signaling may contribute to the development of sporadic chordomas. More importantly, a combination of Akt and mTORC1 inhibition may provide clinical benefits to chordoma patients.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

Infantile clivus chordoma without clivus involvement: case report and review of the literature

BACKGROUND

We present a giant clival chordoma with disseminated disease but without involvement of the clivus. To our knowledge, this is the youngest child and only the second case, presenting without base of skull involvement, in paediatric literature and the fourth reported case of a chordoma in a patient with tuberous sclerosis.

DISCUSSION

We discuss the subtle presentation, difficulties in diagnosis and management and also review the literature.

Cutaneous metastatic chordoma with concomitant tuberous sclerosis

BACKGROUND

Chordomas are rare malignant tumors of notochord origin and are locally aggressive with a metastatic potential. Of noted interest, the skin rarely is seen as a metastatic site.

METHODS AND OBSERVATIONS

We describe a 20-month-old infant whose primary presentation of a clivus-based chordoma was multiple asymptomatic cutaneous nodules. A skin biopsy showed large vacuolated cells embedded in a myxoid stroma. Immunohistochemical staining was positive for S-100, keratin, and epithelial membrane antigen markers consistent with malignant chordoma. Magnetic resonance imaging revealed a clivus-based chordoma with scattered metastases within the neuraxis and multiple visceral sites. Further examination also revealed a diagnosis of tuberous sclerosis.

LIMITATIONS

An observed association between chordoma and tuberous sclerosis cannot be established firmly on the basis of a case report.

CONCLUSIONS

This case illustrates a diagnostic challenge because of the unusual presentation of an already rare tumor. By reporting our case, we hope to assist in the recognition of this rare dermal condition and highlight the speculated coexistence of tuberous sclerosis with chordoma tumors.

Update on the cytogenetics and molecular genetics of chordoma

Chordoma is a rare mesenchymal tumour of complex biology for which only histologic and immunohistochemical criteria have been defined, but no biomarkers predicting the clinical outcome and response to treatment have yet been recognised. We herein review the interdisciplinary information achieved by epidemiologists, neurosurgeons and basic scientists on chordoma, usually a sporadic tumour, which also includes a small fraction of familial cases. Main focus is on the current knowledge of the genetic alterations which might pinpoint candidate genes and molecular mechanisms shared by sporadic and familiar chordomas. Due to the scarcity of the investigated tumour specimens and the multiple chromosome abnormalities found in tumours with aberrant karyotypes, conventional cytogenetics and Fluorescence In Situ Hybridization failed to detect recurrent chordoma-specific chromosomal rearrangements. Genome-wide approaches such as Comparative Genomic Hybridization (CGH) are yet at an initial stage of application and should be implemented using BAC arrays either genome-wide or targeting selected genomic regions, disclosed by Loss of Heterozygosity (LOH) studies. An LOH region was shown by a systematic study on a consistent number of chordomas to encompass 1p36, a genomic interval where a candidate gene was suggested to reside. Despite the rarity of multiplex families with chordoma impaired linkage studies, a chordoma locus could be mapped to chromosome 7q33 by positive lod score in three independent families. The role in chordomagenesis of the Tuberous Sclerosis Complex (TSC) genes has been proved, but the extent of involvement of TSC1 and TSC2 oncosuppressors in chordoma remains to be assessed. In spite of the scarce knowledge on the genetics and molecular biology of chordoma, recent initiation of clinical trials using molecular-targeted therapy, should validate new molecular targets and predict the efficacy of a given therapy. Comparative genetic and biomolecular studies should enhance the molecular taxonomy of chordoma which might have a prognostic significance and better orient the therapeutic options.

Malignant PEComa of the skull base

Perivascular epithelioid cell tumors (PEComas) are rare, usually benign lesions comprising a family of neoplasms including angiomyolipoma, lymphangioleiomyomatosis, clear cell "sugar" tumors, and clear cell myomelanocytic tumors. This report describes an apparent case of a malignant PEComa of the skull base in a 49-year-old woman, a previously undescribed location for this lesion.

Sacrococcygeal chordomas in patients with tuberous sclerosis complex show somatic loss of TSC1 or TSC2

Chordomas are rare sacrococcygeal/sacral, sphenooccipital/clivus, and spinal tumors whose molecular etiology remains relatively understudied. As several anecdotal reports had described chordomas in individuals with tuberous sclerosis complex (TSC), a multisystem hamartoma syndrome, we hypothesized that the genes that cause TSC may have an etiological role in chordomas. In two cases of sacrococcygeal chordomas in individuals with TSC, one with a germ-line TSC2 mutation and the other with a germ-line TSC1 mutation, we confirmed somatic inactivation of the corresponding wild-type allele by loss of heterozygosity analysis and immunohistochemistry. These data provide the first evidence of a pathogenic role by TSC genes in sacrococcygeal chordomas.

Mapping of candidate region for chordoma development to 1p36.13 by LOH analysis

Various cytogenetic and molecular findings indicate 1p36 loss as a consistent change in sporadic and inherited chordoma, a rare embryogenetic neoplasm arising from notochord remnants. We studied 27 sporadic chordomas by means of loss of heterozygosity (LOH) of 31 microsatellites localized to the 1p36.32-36.11 region, and restricted the minimal LOH interval shared by 85% of the tumours to 1p36.13. We also used RT-PCR analysis to investigate the role of the candidate genes CASP9, EPH2A, PAX7, DAN and DVL1, which were selected on the basis of the physical mapping of the LOH region and their plausible oncosuppressor function. RT-PCR analysis showed the presence of DAN and PAX7 transcript fragments of the expected size in all of 8 chordoma samples, whereas the CASP9-specific fragment was observed in only 3 and EPH2A was absent in one. Smaller than expected DVL1 transcripts were found in 4 tumours as well as in their normal counterpart (nucleus pulposus), which also showed a typically sized transcript. Sequencing revealed the skipping of 3 exons in the smallest DVL1 fragment, thus leading to a frameshift and predicting a truncated DVL1 gene product. Our study of the largest cohort of chordoma patients recruited so far indicates a common molecular lesion at 1p36.13, and suggests that the CASP9, EPH2A and DVL1 genes may play an onco-suppressing role and be involved in the development of chordoma.