A Novel Osteosarcoma Gene and Therapeutic Pathway: Paradigm for Diagnosis and Treatment

By Olga Camacho-Vanegas, PhD and John Martignetti, MD, PhD

Introduction

Osteosarcoma (OS) is the most frequent primary bone tumor in children and adolescents. Despite all scientific efforts in the last 20 years, the mechanism of OS formation needs to be better understood. In this research, our results identified novel genes that are dysregulated in a high percentage of sporadic OS and highlight methylation as one of the potential pathways affected by MTAP_SV dysregulation. These findings link to our previous discovery of the gene defect causing the hereditary bone cancer syndrome DMS-MFH: mutations in three previously unrecognized terminal exons of the methylthioadenosine phosphorylase (MTAP) gene and consequently dysregulated expression of six novel biological active splice isoforms. In support of our previously published data and as part of this research project, we have recently reported dysregulation of MTAP isoforms in a new DMS-MFH family with myopathy component.¹ Our discoveries are important contributions for better understanding the molecular mechanism in OS formation, and eventually to the development of new and more effective treatments.

Specific Aims

Two main aims were proposed in this research project, and we made significant progress in each. First, we have demonstrated in a 'validation' OS sample set that MTAP splice variants pattern is dysregulated in OS. Second, we have identified differentially methylated candidate genes in OS cell lines expressing MTAP isoforms that are potentially involved in OS formation. Our project was based on our recently published findings that mutations in the methylthioadenosine phosphorylase (MTAP) gene resulted in a novel osteosarcoma syndrome and that dysregulated expression of MTAP was prevalent in all, hereditary and non-hereditary, forms of osteosarcoma.

Aim #1. Define the frequency and mechanisms of dysregulated MTAP splice variant expression in osteosarcoma.

DMS-MFH is an autosomal dominant bone dysplasia / bone cancer syndrome, wherein 35% of affected individuals develop bone MFH or osteosarcoma. Using a genetic linkage analysis, we previously mapped the DMS-MFH gene locus to chromosome 9p21-22 and demonstrated that this bone cancer syndrome results from mutations in three previously unrecognized terminal exons of the MTAP gene. Specifically, we have discovered that the MTAP gene actually encodes 6 novel biologically active splice variants and that these variants are dysregulated in familial OS.² Based on similarities between familial and sporadic OS suggesting that both share the same ethology, we decided to investigate if this familial bone cancer syndrome gene defect is also at the basis of the molecular origins of highly malignant hereditary and sporadic bone sarcoma.

Our preliminary results from analysis made in a 'screening' OS sample set provided the first evidence that MTAP isoform pattern was dysregulated in the majority of OS samples. To corroborate our previous results, we have examined the expression of MTAP archetype, _SV1, and _SV3 splice variants at RNA level in a larger 'validation' sample set of OS grade IV samples with confirmed osteoblactic/fibroblastic hystiotype (n= 43), two familial OS and in three osteoblastic cell lines used as controls. Quantitative RT-PCR analysis using specific primers revealed that MTAP archetype was expressed in all the samples. Importantly and in agreement with our preliminary results, MTAP_SV3 levels were significantly higher in the majority of OS samples (>75%) when compared to the controls (p value: 0.043087) (Figure 1A and Figure 1B) and quantifiable levels of MTAP_V1 were not consistently detected in any of the OS samples. These findings demonstrate that frequency of loss of MTAP expression is higher than previously recognized in sporadic OS, and we believed this important discovery will help to undercover target genes that are affected when methionine and adenine salvage pathways are inhibited.

MTAP is a ubiquitous enzyme that plays an important role in the MTA salvage pathway for adenine and methionine production.³ Cells lacking MTAP activity are unable to metabolize MTA, and functional inhibition or dysregulation of MTAP activity would therefore be expected to result in intracellular MTA accumulation and secretion.^4,5 In fact this is the case for DMS-MFH patients, wherein we have previously demonstrated accumulation of MTA in their serum. Because methionine is one of the sub-products of the MTA salvage pathway and the principal source of methyl groups in the cell, we investigated if methylation is one of the molecular mechanism(s) affected by splice variant (MTAP_SV) dysregulation.

We examined the methylation status of the entire genome of previously engineered MTAP null osteosarcoma MNNG-HOS cell lines expressing MTAP archetype, _SV1, and _SV3 versus control Lacz, using the Infinium Human Methylation 450K array. This array allows interrogation of >485,000 methylation sites per sample at single-nucleotide resolution, and it covers 99% of RefSeq genes (defines genomic sequences to be used as reference standards for well-characterized genes), with an average of 17 CpG sites per gene region distributed across the promoter, 5'UTR, first exon, gene body, and 3'UTR. Results from computation analysis comparing methylated gene status of MTAP archetype, _SV1, and _SV3 against the control Lacz, revealed a unique candidate list containing 362, 472, 365 differential methylated genes (DMG) respectively. To further select candidate DMG genes, we performed an in silico literature search for gene function and pathway analysis to the top 10% more DMGs. Our parameters of selection were for genes involved in cell cycle control, apoptosis, metastasis and bone differentiation. In total we have selected 20 candidates relevant cancer DMGs. Interestingly, for cells expressing MTAP_SV1, the number of DMGs involved in the cancer related pathway was higher than those for cells expressing archetype MTAP or _SV3 (Table 1A, 1B and 1C). Of particular interest, our candidate gene list includes members (TGF-β, Ski, ATF2, Nodal, SMAD1) of the TGF-β and BMP signaling pathways.

The TGF-β superfamily includes proteins that regulate cellular functions such as proliferation, apoptosis, differentiation, migration, and angiogenesis. TGF-β can inhibit or promote the cell cycle depending on the cellular context, including the stage of the disease and the local environment. In early cancers stages, it acts as a tumor suppressor gene and in advance stages it favors tumor development. TGF-β overexpression associated with enhanced invasiveness has been reported in different kind of tumors including breast, colon, esophageal, gastric, liver, lung kidney, pancreas, prostate and brain.⁶ Of therapeutic relevance, it has been shown that TGF-β is capable of inducing angiogenesis directly and indirectly. It has also been reported that endoglin, a transmembrane glycoprotein overexpressed by vascular endothelial cells during proliferation, acts as a co-receptor and interacts with TGF-β, protecting endothelial cells from the inhibitory properties of TGF-β. Endoglin activates ALK-1, which phosphorylates the alternative Smads (Smad1, Smad5, and Smad8) that promote endothelial cell proliferation, migration, and the transcription of other proangiogenic genes.⁷ Recently, Nodal signaling was linked to a more aggressive phenotype in melanoma and breast cancer cells and to malignancy in the pancreas, but not to normal cells.^8,9 Furthermore, inhibition of Nodal/Activin signaling has been shown to reduce tumorigenicity in melanoma cell lines,¹⁰ and to abrogate self-renewal capacity and in vivo tumor formation in pancreatic cancer stem cells.⁹ Therefore, inhibition of the Nodal/Activin pathway provides a therapeutic strategy for targeting cancer stem cells.

In total we have now identified 15 potential candidate DMG involved in control of cell proliferation, apoptosis, angiogenesis and bone morphogenesis. We will now move into the validation phase at the RNA and genomic DNA level. If our selected candidate genes hold the validation phase, this will be a major turning point of how methylation studies uncover new pathways that can be targeted to develop new treatment strategies for OS.

Aim #2. Determine the therapeutic sensitivity of cells with dysregulated MTAP_SV expression patterns to MTAP-targeted therapies.

Since the discovery of MTAP deficient tumors, many efforts have been made to design new strategies to selectively target MTAP lacking cells. It has been long recognized that cells lacking MTAP are more sensitive to inhibitors of novo purine synthesis than cells containing MTAP. Recently, a promising novel treatment has been reported that targets MTA deficient cells with a combination of toxic purine or pyrimidine analogs. With this treatment, it is expected that MTA produced by normal cells will block the conversion of the analog to its toxic nucleotide. MTAP deficient cells will not be able to block this conversion and therefore the cells will be selectively killed by the analog’s toxic effect.¹¹

Because our hypothesis is that a majority of osteosarcoma tumor cells are MTAP deficient, through the dysregulation of MTAP splice variants, we decided to investigate the potential of this treatment for OS. Specifically, we tested a combination of toxic purine analogs and either MTAP substrate, MTA or 5’-dAdo, to target MTAP dysregulated engineered OS cell lines. MNNG-HOS cell lines expressing combinations of MTAP archetype, and _SV1, _SV2 and _SV3 and Lacz as control were treated for 48 hours with DAP (0.5, 2, 10 and 50 μM), 6-TG (0.5, 2, 10 and 50 μM), or 5-FU (0.5, 2, 10 and 50 μM) with or without the MTAP substrate MTA (30 μM) or 5’-dAdo (30 μM). MTT cell viability assay showed no significant differences in the ability of this treatment to target cells that express any of the combinations mentioned above. We have previously shown that the MTAP gene codifies for six biological active isoforms and that precise pattern expression of these variants is important for MTAP activity. The present results suggest that further experiments need to be done using different MTAP-SV combinations in order to establish the critical one to properly have MTAP activity.

Conclusion

Our results provide the first evidence of the loss of MTAP splice variants in a high percentage of sporadic OS. We have demonstrated in a validation sample set that 75% (30/43) of OS samples have increased expression of MTAP_SV3 and all samples lack MTAP_SV1. Furthermore, we have identified 15 differential methylated genes in engineered MTAP-null osteosarcoma cell lines expressing archetype MTAP, _SV1 and _SV3, which potentially will give insights into the mechanism at basis of the origin of OS. Importantly, in this list of DMR, the identification of TGF-β, Ski, ATF2, Nodal and SMAD1 members of the TGF-β signaling pathway offers a new and important avenue for translational research, with the potential to treat OS with abnormal expression of any of the TGF- β pathway proteins.

Copyright © 2015 Liddy Shriver Sarcoma Initiative.

The Therapeutic Relevance of MTAP Dysregulation in Osteosarcoma and MFH of the Bone

An ESUN Experimental Plan
By Olga Camacho-Vanegas, PhD and John Martignetti, MD, PhD

Introduction

We have identified a novel gene which we believe is dysregulated in a majority of sporadic osteosarcoma (OS) tumor samples. This discovery was based on the identification of the gene mutation which causes a hereditary form of osteosarcoma and malignant fibrous histiocytoma of bone. DMS-MFH is an autosomal dominant bone dysplasia / bone cancer syndrome, wherein 35% of affected individuals develop bone MFH or osteosarcoma. Using a genetic linkage analysis/positional gene cloning based approach, we demonstrated that mutations in and dysregulated expression of three previously unrecognized terminal exons of the methylthioadenosine phosphorylase (MTAP) gene, which encode six biologically active, novel splice isoforms result in this hereditary bone sarcoma syndrome. MTAP is a ubiquitously expressed homotrimeric-subunit enzyme critical to polyamine metabolism and adenine and methionine salvage pathways. Until our discovery, it was believed to be encoded as a single transcript from eight exons. Each of the novel isoforms can physically interact with archetype MTAP (i.e., exons 1-8). Based on these findings, we then analyzed the expression of these MTAP isoforms in a "discovery" sample set (n=16) of sporadic osteosarcoma samples. While the majority of tumor samples expressed similar levels of the archetype MTAP RNA sequence the expression pattern of the splice variants varied markedly between nearly all the samples. Nearly 75% of samples failed to express the biologically active dominant splice form, MTAP-SV1.

We therefore propose two interconnected specific aims critical for us to move beyond the "discovery phase." First, we aim to define the frequency and mechanism of MTAP splice variant dysregulation/MTAP deficiency in sporadic osteosarcoma.  Second, we will examine if MTAP splice deficient cells – which we hypothesize to represent the largest fraction of osteosarcomas – are sensitive to inhibitors of de novo purine synthesis.

If successful, the overarching goals of these studies will provide insight into the frequency of loss of these novel MTAP splice variants in sporadic osteosarcoma and the therapeutic relevance of detecting their alteration and then using this information to treat tumor cells. These preclinical studies are aimed at future therapeutic uses in individuals with osteosarcoma.

Background

To date, many of the insights into osteosarcoma (OS) genetics have come from the study of familial cancer syndromes. Universally, these syndromes have a low frequency (< 10%) of predisposition to the development of OS. These syndromes include Li-Fraumeni syndrome (mutations in P53), Rothmund-Thomson, Bloom, and Werner syndromes (RecQ helicase family), and hereditary retinoblastoma (Rb). We have now identified the genetic mutation which results in a hereditary osteosarcoma syndrome in which 35% of affected individuals develop OS and/or bone MFH.

Of particular therapeutic relevance, this gene encodes an enzyme - methylthioadenosine phosphorylase (MTAP) - which is therapeutically targetable. The MTAP gene encodes a ubiquitously expressed enzyme that plays a crucial role in the salvage pathway for adenine and methionine in all tissues.¹ In the salvage pathway, methylthioadenosine (MTA), a by-product of the polyamine pathway, is recovered through its phosphorolysis into adenine and methylthioribose-1-phosphate by MTAP.² Through a series of reactions, methylthioribose-1-phosphate is then converted into methionine.^2,3 However, in MTAP deficient cells, MTA is not recovered and the salvage pathway for adenine and methionine is not present in these cells. Loss of MTAP activity has previously been suggested to play a role in human cancer and its absence has been reported in a number of cancers including OS.^4,5

Indeed, in one of these osteosarcoma studies,⁶ it was presciently noted that "Cancer cells lacking the MTAP gene are not able to salvage adenine from MTA and, therefore, are more dependent on the de novo synthesis of purines. This absence of MTAP function therefore makes the cells more susceptible to inhibitors of de novo purine biosynthesis including methotrexate." As we describe below in our preliminary results, we believe the loss of MTAP expression is markedly higher in OS than previously suggested and the mechanism of this loss is novel. Taken together, we believe our findings argue that MTAP-targeted treatment in OS is even more clinically relevant than previously appreciated.

Preliminary Results

I. DMS-MFH: an hereditary MFH and OS syndrome

Diaphyseal medullary stenosis with malignant fibrous histiocytoma (DMS-MFH) is a rare, autosomal dominant bone dysplasia / bone sarcoma syndrome (MIM 112250). The bone dysplasia is uniquely characterized by cortical growth abnormalities, including diffuse DMS with overlying endosteal cortical thickening and scalloping, metaphyseal striations, infarctions, and scattered sclerotic areas of the long bones. Clinical features include pathological fractures with subsequent poor healing or nonunion, progressive wasting and bowing of the legs, and painful debilitation. Most notably, 35% of affected individuals develop either MFH, and as we have most recently demonstrated, OS between the second and fifth decades of life.^6-9 Because sporadic and inherited forms of cancer are often genetically equivalent, we hypothesized that identification of this familial syndrome gene would provide insight into the molecular origins of a highly malignant hereditary and sporadic bone sarcoma.

II. Disease gene discovery: Novel splice forms of the MTAP gene

To identify the causative gene, and therefore gain insight into the genetic basis of MFH and OS, we used a positional cloning approach. We originally localized the disease gene to chromosome 9p21-22.^10,11 Interestingly, this locus is one of the most frequently deleted and/or translocated chromosomal regions in human cancer¹² including, most notably, osteosarcoma.^13,14

We have now identified and characterized the genetic defect. We have identified mutations in the most proximal of three previously unknown terminal exons in the methylthioadenosine phosphorylase (MTAP) gene (Figure 1).⁹ The disease-causing mutations do not result in amino acid changes but instead result in exon skipping and subsequent dysregulated expression of these six newly described exons in alternatively spliced, biologically active isoforms (Figure 2).

III. MTAP and Osteosarcoma

The MTAP gene encodes a ubiquitously expressed enzyme that plays a crucial role in the salvage pathway for adenine and methionine in all tissues (Figure 3).^1,2 In the salvage pathway, methylthioadenosine (MTA), a by-product of the polyamine pathway, is recovered through its phosphorolysis into adenine and methylthioribose-1-phosphate by MTAP.² Through a series of reactions, methylthioribose-1-phosphate is then converted into methionine.^1,2 However, in MTAP deficient cells, MTA is not recovered and the salvage pathway for adenine and methionine is not present in these cells.

We have now demonstrated that dysregulation of the novel MTAP splice variants is associated with an increase of MTA in the serum of affected individuals suggesting that dysregulated expression of these isoforms inhibits MTAP activity even in the presence of the enzyme (Table 1).⁹

As we describe below, we believe the loss of MTAP expression is markedly higher in OS and thus targeted treatment is especially clinically relevant.

IV. Loss of MTAP splice variant expression in OS is a high frequency event.

Given the overlap of DMS-MFH molecular findings in relation to OS⁹ and to better explore the relationship between MTAP and sporadic OS, we analyzed the splicing pattern of the MTAP gene in a "discovery set" of sporadic OS samples. All tumor samples (n=16) were positive for archetype MTAP RNA expression (Figure 4, top row). In accord with our hypothesis, the expression pattern of the splice variants varied markedly between nearly all the samples. The majority of samples did not express SV1 (11/16) (middle row). These findings provide the first evidence that loss of MTAP expression may be much greater than previously recognized in sporadic OS and has potential implications for the treatment of this disease.

Research Plan and Experimental Design

Based on our preliminary results we propose two interconnected specific aims:

Aim #1. Define the frequency and mechanism of dysregulated MTAP splice variant expression in osteosarcoma.

Our hypothesis, based on preliminary results in a small sample set, is that MTAP splice variants are dysregulated in a majority of osteosarcoma tumors. This specific aim has two sub aims.

First, we will examine splice pattern expression in a larger, multi-institutional collection of samples. Specifically, a total of 50 samples will be analyzed. As we have already described,⁹ RNA will be extracted from fresh-frozen specimens. cDNA will be prepared from 1 µg of RNA and levels of expression of each MTAP splice variant will be determined by RT-PCR and qRT-PCR using MTAP splice-specific primers.⁹ Expression of p15 and p16 will also be determined. We will focus on correlating MTAP splice levels with linked clinical characteristics including age at diagnosis and survival time. Kaplan-Meier plots and Cox model analyses will be used. Univariate associations between expression patterns and clinical outcomes will be defined using standard regression models. Future studies will be designed to tap into the data arising from the currently ongoing genomic studies of OS and when larger sample sets are available will be used to analyze correlation with histological subtype, site of primary tumor, type of specimen, the presence or absence of metastasis at diagnosis, and Huvos grade.

Second, will investigate the genetic mechanism(s) underlying MTAP splice variant dysregulation. Our original hypothesis had been that altered splicing in sporadic tumors was the result of additional sequence changes/mutations in/adjacent to MTAP exon 9. Intriguingly, we have sequenced the coding region and intron/exon boundaries of MTAP exon 9 in all the samples represented in Figure 4. In contrast to our original hypothesis, no exon 9 mutations were identified in any of the tumor samples. Thus, the mechanism of altered splicing may be a genetic change beyond the current range of detection of our primers or may be secondary to altered methylation. Therefore, we propose to use next-generation sequencing techniques to sequence the entire ~250 KB that includes MTAP, Ink4a/ARF gene locus (chr9: 21,790,000-22,150,000) from 15 paired tumor-normal samples which have demonstrated MTAP splice variant dysregulation (identified in the first sub aim). This will have the added benefit of identifying additional MTAP locus mutations in very high depth from the region – and could be used to supplement OS genome studies. Furthermore, the Ink4a/ARF locus will be included to examine if additional mutations in this locus may modify the effect of MTAP mutations. We will use Agilent's SureSelect DNA Capture System as an enrichment methodology to isolate the defined genomic region. Capture enriched DNA will be sequenced using the HiSeq Illumina platform (MSSM DNA Core). Methylation differences and patterns will also be defined for these samples. For methylation studies we will use the Infinium HumanMethylation450 BeadChip (MSSM DNA Core). While this technology will assay the methylation status of the entire genome and could be viewed as "overkill," in practical reality the efficiency and cost of the analysis renders multiple assays targeting only the MTAP locus both cost and time inefficient.

Aim #2: Determine the therapeutic sensitivity of cells with dysregulated MTAP splice variant expression patterns to MTAP-targeted therapies.

Our hypothesis that a majority of osteosarcoma tumor cells are MTAP deficient, through the dysregulation of MTAP splice variants, leads to our proposal to selectively target these tumor cells.  It has long been known and theorized that MTAP deficient cells are more sensitive to inhibitors of de novo purine synthesis and methionine deprivation.¹⁵ A novel therapy that selectively kills MTAP deficient tumor cells and uses a combination of toxic purine analogs and either MTAP substrate, MTA or 5’-dAdo has recently been described.¹⁶ In addition, the amino acid analogue L-alanosine which interferes with de novo AMP synthesis has also been suggested as an ideal candidate therapy for MTAP deficient tumors.¹⁷  The ability of these strategies to target MTAP splice dysregulated tumors has never been tested. 

Using patient-derived and MTAP splice dysregulated engineered cell lines, we will directly test the ability of these treatments to target MTAP dysregulated cells. For these studies we have already characterized a number of osteosarcoma cell lines (MG-63, Saos-2, U-2 OS and MNNG-HOS) for their expression of archetype MTAP (exons 1-8) and the newly described splice forms. The MNNG-HOS cell line was derived from an osteogenic sarcoma in a Caucasian female age 13 years and which forms tumors in mice.¹⁸ Sequence analysis confirms that this cell line is MTAP deficient (unpublished results). Based on these findings, we have engineered and validated a panel of MNNG-HOS cell lines which express combinations of archetype MTAP and the different splice variants.

Two parallel lines of therapeutic strategies will be pursued. In the first, we will test the adenine analog DAP and two drugs that are currently clinically used, 6-TG or 5-FU, in combination with MTA or 5’-dAdo. In the second, L-alanosine and methionine deprivation will be used. Our use of L-alanosine and methionine deprivation in these studies is not an indication of our belief that this will be a future therapeutic. Instead, it is meant to represent a paradigm for how drugs might be selected for inclusion in these trials. In each the effects of treatment will be tested on cell proliferation and apoptosis. Initially, the IC50 for each drug will be established for each cell line. For the combination analog/MTA treatment, cells will be cultured for three days using calculated IC10, IC25, IC50 and IC85 doses of DAP, 6-TG, or 5-FU with or without the MTAP substrate MTA (15 μM) or 5’-dAdo (15 μM). To quantify drug effects on cell viability, after the third day: 1) we will determine the IC50 using an MTT assay, 2) cells will be trypsinized for determination of cell number and make serial dilutions into complete medium for clonogenic assay. After 2-3 weeks when colonies reach visible size they will be stained with crystal violet in saline/methanol solution and count. Photomicroscopy, will be made to culture dishes before and after treatment. Each experiment will be done three times in triplicate. Student t-test will be used to evaluate the significance of differences between groups, with p<0.05 considered significantly different.

Impact Statement

We believe our initial finding that the MTAP gene is alternatively spliced and that these splice forms can be dysregulated in osteosarcoma are of particular clinical relevance. The studies proposed as part of the Liddy Shriver Sarcoma Initiative aim to provide the first evidence that these variants are dysregulated in a majority of osteosarcomas and that this dysregulation may provide an inroad into targeted therapy.

Future Directions

Based on the results obtained in these proposed studies, we will move future studies in two primary directions.  First, we will increase the sample sizes examined to achieve statistical power to correlate the expression pattern of MTAP splice variants with additional important clinical outcomes (some mentioned above) including survival.  This increase in sample size can be achieved either through collection of additional samples and/or analysis of RNASeq/expression analysis studies which are part of the ongoing OS genome project (we have already initiated discussions with the appropriate representatives of this project).  Second, based on the in vitro studies proposed above, we will then move forward with in vivo studies. If we verified our hypothesis, the next step that we will undertake is to test in vivo the efficiency of candidate therapies.  With this in mind, the cell lines we selected for our studies are tumorigenic.

Summary

This proposal is focused on understanding the role of newly identified, biologically active splice forms of the MTAP gene in osteosarcoma. Specifically, these findings have the potential to provide not only new diagnostic tools for predicting outcome but also suggests a therapeutic approach based on previously established strategies and drug regimens.

V9N5 ESUN Copyright © 2012 Liddy Shriver Sarcoma Initiative.

$50K Grant Funds Bone Sarcoma Research

An ESUN Announcement

The Liddy Shriver Sarcoma Initiative has awarded a $50,000 grant to fund promising research on osteosarcoma and malignant fibrous histiocytoma (MFH) of the bone by investigators at Mt. Sinai School of Medicine. The researchers, Dr. John Martignetti and Dr. Olga Camacho-Vanegas, believe that they have discovered a genetic change that might lead to new targeted treatment for osteosarcoma and MFH patients.

Osteosarcoma and MFH of the bone are rare cancers that usually affects children, adolescents and young adults. The diseases are treated with a combination of aggressive therapies, but a significant number of patients deal with disease relapse and progression. The researchers believe that this study addresses a critical issue for patients and their families: improved treatment.

The work that led to this study began with Dr. Martignetti's encounter with a patient more than a decade ago. Dr. Martignetti and his team discovered that the patient and his family were dealing with a previously undiscovered bone sarcoma syndrome. The team soon started a worldwide search to find others with the same disease. The investigators were able to identify seven different families from around the world who have inherited this genetic condition. Dr. Martignetti says the interactions with these families have inspired his work, "Knowing each of the family members, and over this length of time, is a personal driving force for me to understand more about the disease and what can be done to treat it."

While working with these families, the research team discovered that the MTAP gene plays an important role in the development of familial bone sarcomas. They also believe that their findings will apply to the broader population of bone sarcoma patients. In fact, they think that all bone sarcomas can be divided into two types: those with and those without dysregultion of the MTAP gene. The researchers add, "This knowledge is important because a number of chemotherapies exist that are believed to effectively treat tumors which have defects in MTAP."

The Funding

This $50,000 grant was made possible by a generous donation from Laura Somerville and by donations from Julie Gordon of Brandon’s Defense Foundation (in Memory of Brandon Gordon), Lori Brasic of Soccer ‘Round the Clock (in honor of Logan Brasic), Kim Pidgeon of Sarah’s Garden of Hope (in memory of Sarah Pidgeon) and from the friends and families of Jonah Chrisman and Sara Corbelli, both of whom lost their lives to osteosarcoma.

V9N5 ESUN Copyright © 2012 Liddy Shriver Sarcoma Initiative.