Rhabdomyosarcoma in children

Is there a need for dedicated bone imaging in addition to 18F-FDG PET/CT imaging in pediatric sarcoma patients?

PURPOSE

Many children with sarcomas undergo whole body 2-deoxy-2-((18)F)fluoro-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and technetium methylene diphosphonate ((99)Tc-MDP) studies. It is unknown whether the combination of both tests results in more accurate detection of bone lesions than (18)F-FDG- PET/CT alone.

METHODS

(99)Tc-MDP bone and (18)F-FDG PET/CT scans were each read by 2 "blinded" observers and then reviewed side-by-side by 3 readers. Bone lesions were graded qualitatively on a 5-point scale (from benign to malignant). Clinical and imaging follow-up (n = 21) and bone biopsy results (n = 8) served as reference standard.

RESULTS

A total of 39 paired (99)Tc-MDP and (18)F-FDG-PET/CT studies (cases) performed at a mean interval 4 ± 7 days, were performed on 29 patients (mean age 12 ± 5 y). Of these, 21 patients (72%) had bone sarcoma, whereas 8 patients (28%) had soft tissue sarcoma. By patient and case-based analysis, (18)F-FDG PET/CT had an accuracy of 100%. Tc-MDP had accuracies of 90% and 82% by patient and case-based analysis. The combined interpretation had an accuracy of 97%.

CONCLUSIONS

In this study, (99)Tc-MDP bone imaging does not provide an added diagnostic value for bone involvement over (18)F-FDG-PET/CT.

Protein kinase C iota as a therapeutic target in alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcoma is an aggressive pediatric cancer exhibiting skeletal muscle differentiation. New therapeutic targets are required to improve the dismal prognosis for invasive or metastatic alveolar rhabdomyosarcoma. Protein kinase C iota (PKCι) has been shown to play an important role in tumorigenesis of many cancers but little is known about its role in rhabdomyosarcoma. Our gene expression studies in human tumor samples revealed overexpression of PRKCI. We confirmed overexpression of PKCι at the mRNA and protein level using our conditional mouse model that authentically recapitulates the progression of rhabdomyosarcoma in humans. Inhibition of Prkci by RNA interference resulted in a dramatic decrease in anchorage-independent colony formation. Interestingly, treatment of primary cell cultures using aurothiomalate (ATM), which is a gold-containing classical anti-rheumatic agent and a PKCι-specific inhibitor, resulted in decreased interaction between PKCι and Par6, decreased Rac1 activity and reduced cell viability at clinically relevant concentrations. Moreover, co-treatment with ATM and vincristine, a microtubule inhibitor currently used in rhabdomyosarcoma treatment regimens, resulted in a combination index (C. I.) of 0.470–0.793 through cooperative accumulation of non-proliferative multinuclear cells in the G2/M phase, indicating that these two drugs synergize. For in vivo tumor growth inhibition studies, ATM demonstrated a trend towards enhanced vincristine sensitivity. Overall, these results suggest that PKCι is functionally important in alveolar rhabdomyosarcoma anchorage-independent growth and tumor cell proliferation and that combination therapy with ATM and microtubule inhibitors holds promise for the treatment of alveolar rhabdomyosarcoma.

Drosophila and mammalian models uncover a role for the myoblast fusion gene TANC1 in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a malignancy of muscle myoblasts, which fail to exit the cell cycle, resist terminal differentiation, and are blocked from fusing into syncytial skeletal muscle. In some patients, RMS is caused by a translocation that generates the fusion oncoprotein PAX-FOXO1, but the underlying RMS pathogenetic mechanisms that impede differentiation and promote neoplastic transformation remain unclear. Using a Drosophila model of PAX-FOXO1-mediated transformation, we show here that mutation in the myoblast fusion gene rolling pebbles (rols) dominantly suppresses PAX-FOXO1 lethality. Further analysis indicated that PAX-FOXO1 expression caused upregulation of rols, which suggests that Rols acts downstream of PAX-FOXO1. In mammalian myoblasts, gene silencing of Tanc1, an ortholog of rols, revealed that it is essential for myoblast fusion, but is dispensable for terminal differentiation. Misexpression of PAX-FOXO1 in myoblasts upregulated Tanc1 and blocked differentiation, whereas subsequent reduction of Tanc1 expression to native levels by RNAi restored both fusion and differentiation. Furthermore, decreasing human TANC1 gene expression caused RMS cancer cells to lose their neoplastic state, undergo fusion, and form differentiated syncytial muscle. Taken together, these findings identify misregulated myoblast fusion caused by ectopic TANC1 expression as a RMS neoplasia mechanism and suggest fusion molecules as candidates for targeted RMS therapy.

Urogenital tumours in childhood

The commonest urogenital tumours in childhood are Wilms tumour of the kidney and rhabdomyosarcoma in the pelvis. We review these tumours along with other primary renal tumours and less common ovarian and testicular tumours in childhood. Current clinical concepts, relevant staging investigations and imaging features are described.

Pediatric genitourinary tumors

PURPOSE OF REVIEW

To review the 2009/2010 literature on pediatric genitourinary tumors and highlight the most significant publications.

RECENT FINDINGS

New techniques such as gene expression profiling, PET, nephron-sparing surgery, and stem cell transplantation are being incorporated into contemporary treatments for pediatric patients with genitourinary tumors. Biologic markers are increasingly being used to help with risk stratification of patients. WT1 mutation and 11p15 loss of heterozygosity have been associated with relapse in very low-risk Wilms tumors treated with surgery alone and may help reduce the use of chemotherapy in some children. Discussion continues on the use of fusion gene status to risk stratify alveolar rhabdomyosarcoma. Meta-analysis of the use of high-dose chemotherapy with autologous hematopoetic stem cell rescue in patients with relapsed Wilms tumor and rhabdomyosarcoma suggests that some patients may benefit more from conventional salvage chemotherapy. New agents are needed for patients with high-risk and relapsed disease to improve outcomes.

SUMMARY

In general, the prognosis for patients with pediatric genitourinary tumors is favorable. The elucidation of the molecular abnormalities in these tumors is determining risk stratification, treatment strategies, and candidates for new drug development.

Anovulatory bleeding in a 12-year-old as presenting sign for rare undifferentiated sarcoma

BACKGROUND

Abnormal uterine bleeding is a common phenomenon in perimenarchal females. Though most cases of abnormal bleeding are due to anovulatory bleeding or bleeding disorders, rare cases are attributable to underlying malignancy.

CASE

Here we report a 12-year-old female patient who presented with abnormal uterine bleeding three months after menarche. She was ultimately diagnosed with a pelvic sarcoma of unknown primary origin. She was subsequently treated with chemotherapy, whole pelvic radiation, and hysterectomy with bilateral salpingo-oophorectomy.

SUMMARY

Abnormal uterine bleeding unresponsive to conventional temporizing measures should be thoroughly evaluated. Management of pelvic malignancies in the pediatric population requires cooperation amongst specialists from an array of disciplines.

Congenital tumors: imaging when life just begins

BACKGROUND: The technical developments of imaging methods over the last 2 decades are changing our knowledge of perinatal oncology. Fetal ultrasound is usually the first imaging method used and thus constitutes the reference prenatal study, but MRI seems to be an excellent complementary method for evaluating the fetus. The widespread use of both techniques has increased the diagnosis rates of congenital tumors. During pregnancy and after birth, an accurate knowledge of the possibilities and limits of the different imaging techniques available would improve the information obtainable, thus helping the medical team to make the most appropriate decisions about therapy and to inform the family about the prognosis. CONCLUSION: In this review article, we describe the main congenital neoplasms, their prognosis and their imaging characteristics with the different pre- and postnatal imaging methods available.

Tumor volume and patient weight as predictors of outcome in children with intermediate risk rhabdomyosarcoma: a report from the Children's Oncology Group

BACKGROUND

The objectives of this study were to compare tumor volume and patient weight versus traditional factors of tumor size (greatest dimension) and patient age and to determine which parameters best discriminated outcome among pediatric patients with intermediate-risk rhabdomyosarcoma (RMS).

METHODS

Complete information was available for 370 patients with nonmetastatic RMS who were enrolled in the Children's Oncology Group (COG) intermediate-risk study D9803 (1999-2005). The Kaplan-Meier method was used to estimate survival distributions. A recursive partitioning model was used to identify prognostic factors that were associated with event-free survival (EFS). Cox proportional hazards regression models were used to estimate the association between patient characteristics and the risk of failure or death.

RESULTS

For all patients with intermediate-risk RMS, a recursive partitioning algorithm for EFS suggested that prognostic groups should be defined optimally by tumor volume (with a transition point at 20 cm(3) ), patient weight (with a transition point at 50 kg), and embryonal histology. Tumor volume and patient weight added significant outcome information to the standard prognostic factors, including greatest tumor dimension and patient age (P = .02). The ability to resect the tumor completely was not associated significantly with the size of the patient, and patient weight did not significantly modify the association between tumor volume and EFS after adjustment for standard risk factors (P = .2).

CONCLUSIONS

The factors that had the strongest association with EFS were tumor volume, patient weight, and histology. On the basis of regression modeling, tumor volume and patient weight were superior predictors of outcome compared with greatest tumor dimension and patient age in children with intermediate-risk RMS. The current results indicated that the prognostic performance of tumor volume and patient weight should be assessed in an independent prospective study.

Synthetic lethality screens reveal RPS6 and MST1R as modifiers of insulin-like growth factor-1 receptor inhibitor activity in childhood sarcomas

The insulin-like growth factor-1 receptor (IGF1R) is emerging as a promising therapeutic target in human cancers. In the high-risk childhood sarcomas Ewing family tumor and rhabdomyosarcoma, IGF1R-blocking antibodies show impressive antitumor activity in some but not all patients, and acquired resistance is observed. Because tumor IGF1R mutations are not described, the basis of IGF1R inhibitor resistance remains unknown. We hypothesized that compensatory signaling cascades bypassing targeted IGF1R inhibition might be involved. To test this systematically, we performed small interfering RNA (siRNA) screens in sarcoma cell lines to identify IGF1R pathway components or related protein tyrosine kinase (PTK) networks that modulate the antitumor efficacy of the BMS-536924 IGF1R kinase inhibitor. This strategy revealed (a) that sarcoma cells are exquisitely sensitive to loss of distal rather than proximal IGF1R signaling components, such as ribosomal protein S6 (RPS6); (b) that BMS-536924 fails to block RPS6 activation in resistant sarcoma cell lines; and (c) that siRNA knockdown of the macrophage-stimulating 1 receptor tyrosine kinase (MST1R; also known as RON) restores BMS-536924 efficacy, even in highly drug-resistant cell lines. We confirmed MST1R expression across a broad panel of childhood sarcomas, and found that loss of MST1R by RNA interference blocks downstream RPS6 activation when combined with BMS-536924 in vitro. These findings underscore the importance of fully understanding PTK networks for successful clinical implementation of kinase inhibitor strategies.

Activation of the hedgehog pathway confers a poor prognosis in embryonal and fusion gene-negative alveolar rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and comprises two major histological subtypes: alveolar rhabdomyosarcoma (ARMS) and embryonal rhabdomyosarcoma (ERMS). Seventy-five percent of ARMS harbor reciprocal chromosomal translocations leading to fusion genes of the forkhead transcription factor FOXO1 and PAX3 or PAX7. The hedgehog (Hh) pathway has been implied in tumor formation and progression of various cancers including RMS. However, whether Hh pathway activation presents a general feature of RMS or whether it is restricted to specific subgroups has not yet been addressed. Here, we report that marker genes of active Hh signaling, that is, Patched1 (Ptch1), Gli1, Gli3 and Myf5, are expressed at significantly higher levels in ERMS and fusion gene-negative ARMS compared with fusion gene-positive ARMS in two distinct cohorts of RMS patients. Consistently, Gli1 expression correlates with Ptch1 expression in ERMS and fusion gene-negative ARMS, but not in fusion gene-positive ARMS. In addition, expression levels of MyoD1 are significantly lower in ERMS and fusion gene-negative ARMS, pointing to an inverse association of Hh activation and early muscle differentiation. Moreover, Myf5 is identified as a novel excellent class predictor for RMS by receiver operating characteristic analysis. Importantly, high expression of Ptch1 or low MyoD1 expression significantly correlate with reduced cumulative survival in fusion gene-negative RMS underscoring the clinical relevance of these findings. By showing that Hh signaling is preferentially activated in specific subgroups of RMS, our study has important implications for molecular targeted therapies, such as small molecule Hh inhibitors, in RMS.

Pediatric genitourinary tumors

PURPOSE OF REVIEW

To review the 2008-2009 literature on pediatric genitourinary tumors and highlight the most significant publications.

RECENT FINDINGS

New techniques such as gene expression profiling, PET, nephron-sparing surgery, and stem cell transplantation are being incorporated into contemporary treatments for pediatric patients with genitourinary tumors. The WTX gene is the most commonly mutated gene in Wilms tumor, and its product enhances Wilms tumor gene 1-mediated transcription. Germline WTX mutations cause an X-linked sclerosing bone dysplasia but do not appear to predispose to Wilms tumor formation. Protocadherin gene clusters on chromosome 5q31 may act as tumor suppressors. In rhabdomyosarcoma, ILK and platelet-derived growth factor receptor-A join the paired box gene 7 and 3-forkhead box O1 fusions as potential therapeutic targets, and muscle-specific microRNAs offer promise as adjuvant therapy. Despite the high cure rate of Wilms tumor, long-term survivors remain at risk of death from various causes.

SUMMARY

In general, the prognosis for patients with pediatric genitourinary tumors is favorable. The elucidation of the molecular abnormalities in these tumors is determining risk stratification, treatment strategies, and candidates for new drug development.

MYC in oncogenesis and as a target for cancer therapies

MYC proteins (c-MYC, MYCN, and MYCL) regulate processes involved in many if not all aspects of cell fate. Therefore, it is not surprising that the MYC genes are deregulated in several human neoplasias as a result from genetic and epigenetic alterations. The near "omnipotency" together with the many levels of regulation makes MYC an attractive target for tumor intervention therapy. Here, we summarize some of the current understanding of MYC function and provide an overview of different cancer forms with MYC deregulation. We also describe available treatments and highlight novel approaches in the pursuit for MYC-targeting therapies. These efforts, at different stages of development, constitute a promising platform for novel, more specific treatments with fewer side effects. If successful a MYC-targeting therapy has the potential for tailored treatment of a large number of different tumors.