Cetuximab promotes immunotoxicity against rhabdomyosarcoma in vitro

Drugging Hijacked Kinase Pathways in Pediatric Oncology: Opportunities and Current Scenario

Childhood cancer is considered rare, corresponding to ~3% of all malignant neoplasms in the human population. The World Health Organization (WHO) reports a universal occurrence of more than 15 cases per 100,000 inhabitants around the globe, and despite improvements in diagnosis, treatment and supportive care, one child dies of cancer every 3 min. Consequently, more efficient, selective and affordable therapeutics are still needed in order to improve outcomes and avoid long-term sequelae. Alterations in kinases' functionality is a trademark of cancer and the concept of exploiting them as drug targets has burgeoned in academia and in the pharmaceutical industry of the 21st century. Consequently, an increasing plethora of inhibitors has emerged. In the present study, the expression patterns of a selected group of kinases (including tyrosine receptors, members of the PI3K/AKT/mTOR and MAPK pathways, coordinators of cell cycle progression, and chromosome segregation) and their correlation with clinical outcomes in pediatric solid tumors were accessed through the R2: Genomics Analysis and Visualization Platform and by a thorough search of published literature. To further illustrate the importance of kinase dysregulation in the pathophysiology of pediatric cancer, we analyzed the vulnerability of different cancer cell lines against their inhibition through the Cancer Dependency Map portal, and performed a search for kinase-targeted compounds with approval and clinical applicability through the CanSAR knowledgebase. Finally, we provide a detailed literature review of a considerable set of small molecules that mitigate kinase activity under experimental testing and clinical trials for the treatment of pediatric tumors, while discuss critical challenges that must be overcome before translation into clinical options, including the absence of compounds designed specifically for childhood tumors which often show differential mutational burdens, intrinsic and acquired resistance, lack of selectivity and adverse effects on a growing organism.

HER Tyrosine Kinase Family and Rhabdomyosarcoma: Role in Onset and Targeted Therapy

Rhabdomyosarcomas (RMS) are tumors of the skeletal muscle lineage. Two main features allow for distinction between subtypes: morphology and presence/absence of a translocation between the PAX3 (or PAX7) and FOXO1 genes. The two main subtypes are fusion-positive alveolar RMS (ARMS) and fusion-negative embryonal RMS (ERMS). This review will focus on the role of receptor tyrosine kinases of the human epidermal growth factor receptor (EGFR) family that is comprised EGFR itself, HER2, HER3 and HER4 in RMS onset and the potential therapeutic targeting of receptor tyrosine kinases. EGFR is highly expressed by ERMS tumors and cell lines, in some cases contributing to tumor growth. If not mutated, HER2 is not directly involved in control of RMS cell growth but can be expressed at significant levels. A minority of ERMS carries a HER2 mutation with driving activity on tumor growth. HER3 is frequently overexpressed by RMS and can play a role in the residual myogenic differentiation ability and in resistance to signaling-directed therapy. HER family members could be exploited for therapeutic approaches in two ways: blocking the HER member (playing a driving role for tumor growth with antibodies or inhibitors) and targeting expressed HER members to vehiculate toxins or immune effectors.

Targeting EGFR and uPAR on human rhabdomyosarcoma, osteosarcoma, and ovarian adenocarcinoma with a bispecific ligand-directed toxin

Purpose

Human sarcomas are rare and difficult to treat cancerous tumors typically arising from soft tissue or bone. Conversely, carcinomas are the most common cancer subtype in humans and the primary cause of mortality across all cancer patients. While conventional therapeutic modalities can prolong disease-free intervals and survival in some cases, treatment of refractory or recurrent solid tumors is challenging, and tumor-related mortality remains unacceptably high. The identification of overexpressed cell surface receptors on sarcoma and carcinoma cells has provided a valuable tool to develop targeted toxins as an alternative anticancer strategy. Recent investigation of recombinant protein-linked toxins that specifically target these cancer receptors has led to the development of highly specific, cytotoxic, and deimmunized drugs that can kill cancer cells.

Methods

This study investigated a recombinant protein called epidermal growth factor bispecific angiotoxin (eBAT), which is designed to target the epidermal growth factor receptor (EGFR) on cancer cells and the urokinase plasminogen activator receptor (uPAR) on cancer cells and associated tumor vasculature. Both receptors are expressed by a variety of human sarcomas and carcinomas. Flow cytometry techniques were used to determine binding affinity of eBAT to cancer cells, and proliferation assays were performed to calculate tumor killing ability based on half-maximal inhibitory concentrations.

Results

eBAT demonstrated cytotoxicity against a variety of sarcoma and carcinoma cells that overexpress EGFR and uPAR in vitro and showed greater cell killing ability and binding affinity to cancer cells compared with its monospecific counterparts.

Conclusion

The results of our study are promising, and further studies will be necessary to confirm the applicability of eBAT as a supplementary therapy for a variety of sarcomas, carcinomas, and possibly other refractory malignancies that express EGFR and uPAR.

Targeting pediatric sarcoma with a bispecific ligand immunotoxin targeting urokinase and epidermal growth factor receptors

Children with high risk sarcoma have a poor prognosis despite surgical resection, irradiation and chemotherapy. Alternative therapies are urgently needed. Urokinase-type plasminogen activator receptor (uPAR) and epidermal growth factor receptor (EGFR) are surface proteins expressed by some pediatric sarcomas. We show for the first time that a de-immunized bispecific ligand toxin, EGFATFKDEL, directed against EGFR and uPAR, successfully targets pediatric sarcoma. Using flow cytometry, we identified a rhabdomyosarcoma (RMS) cell line, RH30, that expresses both uPAR and EGFR, and a Ewing sarcoma (EWS) cell line, TC-71, that expresses only uPAR. We tested the differential sensitivity of these two sarcoma cell lines to toxin-induced killing, using both in vitro assays and an in vivo murine model. We show that pediatric sarcomas are highly sensitive to EGFATFKDEL (at subnanomolar concentrations) in vitro. In vivo, tumor growth was significantly attenuated after treatment with EGFTFKDEL, compared to untreated controls, in both RH30 and TC-71 tumor bearing mice. In addition, we found that simultaneously targeting both receptors in a dual positive cell line was more effective than targeting a single receptor or antigen, resulting in a greater tumor response, including complete tumor regression in an animal model of bulky disease. Our findings provide support for further exploration of bispecific targeting of pediatric sarcomas with bispecific ligand toxins, such as EGFATFKDEL.

Clinicopathological characteristics and treatment outcomes of Chinese patients with genitourinary embryonal rhabdomyosarcoma

Background

Genitourinary embryonal rhabdomyosarcoma is rarely reported in China. This retrospective analysis aimed to characterize the clinicopathologic features and treatment outcomes of genitourinary embryonal rhabdomyosarcoma in a sample of Chinese patients.

Methods

Basic demographic and clinical data of 29 patients, who were diagnosed with genitourinary embryonal rhabdomyosarcoma between January 2000 and December 2011, were retrieved and analyzed.

Results

In these patients, 25 were males and 4 were females with a median age of 12 years. Paratesticule was the most common lesion site, followed by the prostate, bladder, and vagina. The median tumor size was 5.80 cm. Six patients had clinically positive regional nodes. At the initial diagnosis, patients had a metastatic disease. According to the TNM staging classification for the IRS-IV, phase I lesions were detected in ten cases, phase II lesions in six cases, phase III lesions in four cases, and phase IV lesions in nine cases. The median survival of all patients was 63 (range from 6 to 118) months. The 1-, 3-, and 5-year survival rates for these patients were 93%, 83%, and 52%, respectively. Multivariate analyses demonstrated that staging and anemia were significant predictors of prognosis.

Conclusions

Our findings suggest that metastasis predicts a poor prognosis. Chemotherapy played an important role in comprehensive treatment. Palliative and neo-adjuvant chemotherapy could increase median survival time.

Successful in vivo tumor visualization using fluorescence laparoscopy in a mouse model of disseminated alveolar rhabdomyosarcoma

BACKGROUND

Surgery for rhabdomyosarcoma is challenging due to a lack of clear delineation between tumor and surrounding tissue. Mutilating surgery can be necessary in difficult tumor localizations. Therefore, novel diagnostic and therapeutic modalities are required. The aim of this study was to evaluate the in vivo tumor detection of RMS using fluorescence laparoscopy and to analyze the efficacy of hypericin-induced photodynamic therapy in a mouse model.

METHODS

Seventeen NOD/LtSz-scid IL2Rγnull-mice were divided into four groups. In group 1, mCherry-expressing tumor cells and in group 2-4 non-transfected tumor cells were xenotransplanted. Three weeks later, one fluorochrome per group (ICG, ICG-cetuximab, hypericin) was injected. Fluorescence laparoscopy was carried out and tumors were resected using fluorescence guidance. In the hypericin group, photodynamic therapy was performed using blue light and apoptosis was evaluated by TUNEL test.

RESULTS

A clear discrimination between healthy and tumor tissue was feasible by fluorescending properties with mCherry expressing tumor cells and after injection of hypericin. No fluorescence was detected in mice injected with ICG and ICG-labeled cetuximab. Hypericin photodynamic therapy induced apoptosis of tumor cells after exposure to blue light.

CONCLUSIONS

Intraoperative photodynamic diagnosis was feasible using mCherry-transfected tumor cells or hypericin. Additionally, intraoperative photodynamic therapy was possible and effective.

Cetuximab promotes anticancer drug toxicity in rhabdomyosarcomas with EGFR amplification in vitro

Overexpression of human epidermal growth factor receptor (EGFR) has been detected in various tumors and is associated with poor outcomes. Combination treatment regimens with EGFR-targeting and cytotoxic agents are a potential therapeutic option for rhabdomyosarcoma (RMS) with EGFR amplification. We investigated the effects of combination treatment with actinomycin D and the EGFR-targeting agent cetuximab in 4 RMS cell lines. All 4 RMS cell lines expressed wild-type K-ras, and 2 of the 4 overexpressed EGFR, as determined by flow cytometry, real-time PCR and direct sequencing. Combination of cetuximab and actinomycin D was highly effective, synergistically inhibiting cell growth with a combination index of less than 1. Moreover, combination treatment with these two reagents increased the rate of apoptosis in EGFR-positive cells. Cetuximab has antitumor activity in EGFR-amplified RMS cells when combined with antitumor reagents, indicating that cetuximab is a potential therapeutic reagent for RMS with EGFR amplification.

CXCR7 expression is associated with disease-free and disease-specific survival in cervical cancer patients

BACKGROUND

The CXC chemokine receptor (CXCR)7 is involved in tumour development and metastases formation. The aim of the present study was to determine protein expression of CXCR7, its putative co-receptors epidermal growth factor receptor (EGFR) and CXCR4, its predominant ligand CXCL12, their co-dependency and their association with survival in cervical cancer patients.

METHODS

CXC chemokine receptor 7, EGFR, CXCR4 and CXCL12 expression were determined immunohistochemically in 103 paraffin-embedded, cervical cancers. Subsequently, associations with patient characteristics were assessed and survival analyses were performed.

RESULTS

CXC chemokine receptor 7 was expressed by 43% of tumour specimens, in a large majority of cases together with either EGFR or CXCR4 (double positive), or both (triple positive). The CXCR7 expression was associated with tumour size (P=0.013), lymph node metastasis (P=0.001) and EGFR expression (P=0.009). CXC chemokine receptor 7 was independently associated with disease-free survival (hazard ratio (HR)=4.3, 95% confidence intervals (CI) 1.7-11.0, P=0.002), and strongly associated with disease-specific survival (HR=3.9, 95% CI 1.5-10.2, P=0.005).

CONCLUSION

CXC chemokine receptor 7 expression predicts poor disease-free and disease-specific survival in cervical cancer patients, and might be a promising new therapeutic marker. In a large majority of cases, CXCR7 is co-expressed with CXCR4 and/or EGFR, supporting the hypothesis that these receptors assist in CXCR7 signal transduction.

Immunotherapy: a useful strategy to help combat multidrug resistance

Multidrug resistance (MDR) renders cancer cells relatively invulnerable to treatment with many standard cytotoxic anti-cancer agents. Cancer immunotherapy could be an important adjunct for other strategies to treat MDR positive cancers, as resistance to immunotherapy generally is unrelated to mechanisms of resistance to cytotoxic agents. Immunotherapy to combat MDR positive tumors could use any of the following strategies: direct immune attack against MDR positive cells, using MDR as an immune target to deliver cytotoxic agents, capitalization on other immune properties of MDR positive cells, or conditional immunotoxins expressed under MDR control. Additional insights into the immunogenic potential of some cytotoxic agents can also be brought to bear on these strategies. This review will highlight key concepts in cancer immunotherapy and illustrate immune principles and strategies that have been or could be used to help destroy MDR positive tumor cells, either alone or in rational combinations.

Receptor tyrosine kinases as therapeutic targets in rhabdomyosarcoma

Rhabdomyosarcomas (RMSs) are the most common soft tissue sarcomas of childhood and adolescence. To date, there are no effective treatments that target the genetic abnormalities in RMS, and current treatment options for high-risk groups are not adequate. Over the past two decades, research into the molecular mechanisms of RMS has identified key genes and signaling pathways involved in disease pathogenesis. In these studies, members of the receptor tyrosine kinase (RTK) family of cell surface receptors have been characterized as druggable targets for RMS. Through small molecule inhibitors, ligand-neutralizing agents, and monoclonal receptor-blocking antibodies, RTK activity can be manipulated to block oncogenic properties associated with RMS. Herein, we review the members of the RTK family that are implicated in RMS tumorigenesis and discuss both the problems and promise of targeting RTKs in RMS.