Molecular targeted therapy for metastatic colorectal cancer: current and evolving approaches.

Colorectal cancer (CRC) represents 10% of all cancer types, making it the third leading cause of cancer-related deaths globally. Metastasis is the primary factor causing mortality in CRC patients. Approximately 22% of CRC-related deaths have metastasis present at diagnosis, with approximately 70% of these cases recurring. Recently, with the application of novel targeted drugs, targeted therapy has become the first-line option for individualized and comprehensive treatment of CRC. The management of these patients remains a significant medical challenge. The most prevalent targeted therapies for CRC in clinical practice focus on anti-vascular endothelial growth factor and its receptor, epidermal growth factor receptor (EGFR), and multi-target kinase inhibitors. In the wake of advancements in precision diagnosis and widespread adoption of second-generation sequencing (NGS) technology, rare targets such as BRAF V600E mutation, KRAS mutation, HER2 overexpression/amplification, and MSI-H/dMMR in metastatic colorectal cancer (mCRC) are increasingly being discovered. Simultaneously, new therapeutic drugs targeting these mutations are being actively investigated. This article reviews the progress in clinical research for developing targeted therapeutics for CRC, in light of advances in precision medicine and discovery of new molecular target drugs.

Survival analysis of patients with advanced non-small cell lung cancer receiving EGFR-TKI treatment of Yunnan in southwestern China: a real-world study.

Importance: Patients with EGFR mutations who have advanced-stage non-small cell lung cancer (NSCLC) already receive tyrosine kinase inhibitors (TKIs) as the standard first-line therapy. Notably, Yunnan is a regional high incidence area of lung cancer in the highlands with a high rate of rare EGFR mutations. Overall, lung cancer patients in Xuanwei may present a distinct subgroup globally. Recent studies suggested that the NSCLC cohort in Xuanwei harbored a significantly higher uncommon mutation rate. However, little was known about the clinicopathological features and treatment efficacy of EGFR-TKI in Yunnan NSCLC patients. Objective: This study aimed to investigate the clinical impact of histologic type on the survival outcomes of patients with stage IIIB and IV NSCLC receiving EGFR-TKI treatment of Yunnan in southwestern China. Methods: In this retrospective study, we enrolled advanced NSCLC patients (IIIB-IV) with EGFR mutations who were first diagnosed and treated at Yunnan Cancer hospital from January 2016 to December 2019. Sociodemographics, lifestyle, survival, and clinicopathological characteristics of the patients were collected. The Kaplan-Meier method was used to assess the OS and PFS of patients. An analysis of prognostic factors was conducted using Cox regression. Results: A total of 468 eligible patients were included. The median progression-free survival (PFS) and overall survival(OS) were 11.30(95% CI, 10.12-12.48) months and 30.30(95% CI, 26.24-34.36) months. Based on survival analysis among all the patients,females(HR=0.815;95% CI:0.671-0.989; P=0.017), Xuanwei origin (HR=0.776; 95% CI: 0.609-0.989; P=0.040), sample types(HR=0.780; 95% CI: 0.642-0.947; P=0.012) had a longer PFS. Multivariable analysis showed that only the sample type was an independent factor on median PFS with EGFR-TKI therapy. Patients less than 60 years old (HR=1.433; 95% CI:1.134-1.812, P=0.003)had better OS, but objectives with BMI≥24kg/m2(HR=0.653; 95% CI: 0.500-0.864; P=0.002), females(HR=0.776; 95% CI:0.613-0.982; P=0.035)and patients with tissue sample type (HR=0.760; 95% CI:0.600-.0961; P=0.022) had better OS. Notably, subgroup analysis of our study also found that PFS was significantly better in patients with G719X, L861Q, S768I, G719X+L861Q, and G719X+S768I in Xuanwei than classical mutation ones, including 19-Del and L858R (median 22.7 vs. 12.0 months, HR=0.523, P=0.010), while PFS was inferior in patients with rare mutations of EGFR in non-Xuanwei than the classical mutation ones (median 5.10 vs. 11.10 months, HR=1.760, P=0.015). Conclusion: NSCLC patients in Yunnan displayed a unique EGFR mutation profile, especially a higher prevalence of EGFR uncommon and compound mutations subtype. This study indicates prognostic factors of NSCLC treated with EGFR-TKI in Yunan and Xuanwei. This study will provide new clinical evidence for EGFR-TKI-targeted therapy in patients with rare EGFR mutations in China and worldwide. More researchs were needed for NSCLC EGFR-TKI therapy and medical insurance policy-making in Yunnan, Xuanwei area and uncommon especially.

ISG15 is a potential therapeutic target for osteosarcoma: a comprehensive analysis based on bioinformatics and in vitro experiments.

BACKGROUND: The expression of aberrant interferon-stimulated gene 15 (ISG15) is connected with various human diseases, including cancer. ISG15 is involved in tumor formation and metastasis. However, its role in osteosarcoma is uncertain. METHODS: ISG15 expression in pan-cancer from RNA Sequencing data were obtained from The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression (GTEx) databases. The relationship between ISG15 expression and prognosis was assessed through TCGA clinical survival data. Immunohistochemistry (IHC) images of ISG15 were retrieved using the Human Protein Atlas to analyze the differences in selected normal and tumor tissues. Gene enrichment analysis and signaling pathway analysis were used to assess the potential role of ISG15 in sarcoma, and the correlation between ISG15 expressions and immune cell infiltration levels was estimated by immune infiltration analysis. The expression levels of ISG15 were assessed by qRT-PCR and IHC. Colony formation, wound healing assay and transwell assay were used to detect the effects of ISG15 on the biological behaviors of osteosarcoma cells. The correlation between ISG15 levels and CD8+/CD68+ cells was further examined by double-labeled immunofluorescence. The chemotactic effect of ISG15 on CD8+/CD68+ cells was demonstrated by chemotactic experiments and flow cytometry. RESULTS: ISG15 was highly expressed in most cancers, while high ISG15 expression was significantly correlated with poor overall survival. Gene enrichment analysis in sarcoma suggested that antigen processing and presentation might be involved in the oncogenic mechanism of ISG15. Further immune infiltration analysis showed that high ISG15 expression might reflect the infiltration level of certain immune cells. Additionally, our verification showed that ISG15 was significantly related to the occurrence and metastasis of osteosarcoma, and knockdown of ISG15 significantly altered cell biological behavior, resulting in decreased proliferation, migration and invasion capabilities of osteosarcoma cells. The high expression of ISG15 in osteosarcoma tissue was associated with a high level of CD68+ immune cell infiltration while a low level of CD8+ T cell infiltration. CD68+ immune cells were recruited in vitro by overexpression of ISG15, which on the contrary could weaken the chemotaxis of CD8+ T cells. CONCLUSION: High ISG15 expression is an inherent feature of osteosarcoma and triggers tumorigenesis and metastasis by regulating tumor immunogenicity. ISG15 is expected to be the target of osteosarcoma treatment.

LncRNA TEX41 regulates autophagy by increasing Runx2 expression in lung adenocarcinoma bone metastasis.

OBJECTIVE: To investigate the mechanism underlying the role of TEX41 in lung adenocarcinoma (LUAD) bone metastasis (BM). METHODS: We analyzed the biological functions and molecular mechanisms of TEX41 using bioinformatics. TEX41 and Runx2 expressions were measured in clinical tissue samples and cell lines by quantitative PCR. The effects of TEX41 on LUAD cell proliferation, migration, invasion and metastasis as well as its mechanism of action were investigated. Fluorescence in-situ hybridization (FISH) was performed to determine TEX41 and Runx2 colocalization. Subcutaneous tumor growth and BM were evaluated in nude mice by X-ray and hematoxylin and eosin (HE) staining. RESULTS: TEX41 was dramatically increased in LUAD BM tissue, indicating a poorer prognosis in patients with LUAD and BM. TEX41 knockdown suppressed the migration and metastasis of LUAD cells, whereas TEX41 overexpression promoted these processes. Data from X-ray and HE staining showed that TEX41 supported the BM in LUAD. TEX41 overexpression induced autophagy in LUAD cells, as demonstrated by changes in autophagy markers. Results of FISH showed that TEX41 and Runx2 colocalized in the nucleus, and Runx2 expression was regulated by TEX41. The effects of TEX41 on LUAD cell migration, invasion, metastasis and autophagy were counteracted by Runx2 inhibition. Moreover, the role of TEX41 in the metastasis was partially dependent on autophagy, and phosphoinositide 3-kinase (PI3K)-AKT might be the major signaling pathway involved in TEX41-regulated autophagy. CONCLUSION: TEX41 promotes autophagy in LUAD cells by upregulating Runx2 to mediate LUAD migration, invasion and BM.

Effects of different levels of TGF-ß expression and tumor cell necrosis rates in osteosarcoma on the chemotherapy resistance of osteosarcoma.

PURPOSE: The clinical significance of transforming growth factor ß (TGF-ß) and tumor cell necrosis rate (TCNR) in the expression of osteosarcoma and its effects of chemotherapy resistance on osteosarcoma were explored. PATIENTS AND METHODS: 94 cases of neoadjuvant chemotherapy osteosarcoma patients at the Third Affiliated Hospital of Kunming Medical University between January 2014 and January 2019 were collected. Samples tested for TGF-ß were collected before chemotherapy, the tumor cell necrosis rate of pathological samples before and after chemotherapy was determined. Others analyzed covariates included 12 prognostic factors that may be associated with chemotherapy resistance in previous studies: age, BMI, initial diagnosis time (The time from symptom onset to first medical attention), KPS score, initial tumor size, lymphocytes/leukocytes rate (LWR), neutrophils/lymphocytes rate (NLR), albumin, aspartate transaminase (AST), low density lipoprotein (LDL), blood urea nitrogen (BUN), alkaline phosphatase (ALP), the endpoints included progression-free survival (PFS) and overall survival (OS), response evaluation criteria in solid tumours by RECIST guideline (version 1.1). RESULT: 1. A total of 94 cases were examined for expression of TGF-ß in pathological specimens, 45 cases were TGF-ß high expression (47.9%) and 49 cases were TGF-ß low expression (52.1%); 2. The BMI, LDL, ALP, NLR in TGF-ß high expression group was significantly increased compared to TGF-ß low expression group; the Initial diagnosis time, KPS in TGF-ß high expression group was significantly decreased compared to TGF-ß low expression group, all P < 0.05; 3. Effect of chemotherapy was positively with positive cell rate (P < 0.01 r = 0.337) and TGF-ß total score (P < 0.0001 r = 0.635), while effect of chemotherapy was no correlation with degree of dyeing score (P > 0.05); there was significant difference in change from baseline after chemotherapy between TGF-ß high expression group and TGF-ß low expression group (P = 0.045); 4. Median OS 61.4 months in the TGF-ß high expression group, median OS 68.1 months in the TGF-ß low expression group, one-year survival rate, there was statistically significant difference in two groups (P = 0.045); median PFS 44.8 months in the TGF-ß high expression group, median PFS 56.2 months in the TGF-ß low expression group, There was no statistically significant difference in two groups (P > 0.05); 5. A total of 92 cases were examined for TCNR after chemotherapy, 62 were TCNR ≤ 90% (67.4%), 30 were TCNR > 90% (32.6%); 6. the Initial diagnosis time, KPS, in TCNR > 90% group was significantly increased compared to TCNR ≤ 90% group; the initial tumor size, BUN, ALP in TCNR > 90% group was significantly decreased compared to TCNR ≤ 90% group, all P < 0.05; 7. TCNR was negatively correlated with the change from baseline after chemotherapy (P < 0.001 r = -0.411); there was no statistically significant difference between TCNR > 90% group and TCNR ≤ 90% group in change from baseline after chemotherapy (P > 0.05); 8. Median OS 67.8 months in the TCNR > 90% group, median OS 61.7 months in the TCNR ≤ 90% group, there was statistically significant difference between two groups (P = 0.040); median PFS 57.4 months in the TCNR > 90% group, median PFS 40.5 months in the TCNR ≤ 90% group, there was statistically significant difference between two groups (P = 0.036); 9. TGF-ß total score was negatively correlated with TCNR (P < 0.001 r = -0.571). CONCLUSION: The results of this study suggested that the higher expression of TGF-ß, the lower expression of TCNR, which more likely to induce chemotherapy resistance among patients with osteosarcoma and lead to poor prognosis.

The characteristics of lung cancer in Xuanwei County: A review of differentially expressed genes and noncoding RNAs on cell proliferation and migration.

The occurrence of lung cancers is the highest in Xuanwei County, Yunnan province, China, especially among nonsmoking women. Domestic combustion of smoky coal induces serious indoor air pollution and is considered to be the main cause of human lung cancers. The occurrence of lung cancer in Xuanwei County has unique characteristics, such as the high morbidity in nonsmoking women or people with no family history. In the present review, we summarize advances in identification of differentially expressed genes, regulatory lncRNAs and miRNAs in cell proliferation and migration of lung cancers in Xuanwei County. Moreover, several regulatory differentially expressed genes (DEGs) or noncoding RNAs have diagnostic and prognostic significance for lung cancers in Xuanwei County and have the potential to serve as biomarkers.

Anti-tumor effects and mechanism of GA-13315, a novel gibberellin derivative, in human lung adenocarcinoma: an in vitro and in vivo study.

OBJECTIVE: To investigate the anti-tumor effects and the mechanism of the compound 13-chlorine-3, 15-dioxy-gibberellic acid methyl ester (GA-13315) in lung adenocarcinoma in vitro and in vivo. METHODS: The antiproliferative effect of GA-13313 on the A549 cell line was determined by MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide) assay. A xenograft model of A549 was established to evaluate the anti-tumor effect and histopathological examination was performed to assess the toxicity of GA-13315. Apoptosis was detected by TUNEL staining in tissues and flow cytometry in cells; activation of caspase-3, caspase-8 and caspase-9 was evaluated by immunohistochemical analysis; protein levels of Bcl-2-associated X protein (Bax), B-cell lymphoma-2 (Bcl-2), caspase-4, activating transcription factor 4 (ATF4), glucose-regulated protein 78 (GRP78) and growth arrest and DNA damage-inducible gene 153 (GADD153) were determined by western blotting. Mitochondrial membrane potential (MMP) was measured by the JC-1 fluorescence probe. RESULTS: Our results showed that GA-13315 exhibited potent, dose- and time-dependent anti-proliferative activity, and the IC50 values were 37.43 ± 2.73, 28.08 ± 7.76 and 19.29 ± 7.61 µM at 24, 48, and 72 h, respectively. The xenograft experiment revealed that tumor weight and volume were significantly decreased after GA-13315 3 mg/kg and 9 mg/kg (P < 0.05) treatment, and GA-13315 had low toxicity in bone marrow, kidney and colon tissues. GA-13315 triggered remarkable apoptosis in A549 cells at the concentration of 25.6 µM and 32 µM (P < 0.05) and activated caspase-3, - 8 and - 9. Moreover, GA-13315 induced apoptosis through the mitochondrial apoptosis pathway by elevating the Bax/Bcl-2 ratio, releasing cytochrome c and activating caspase-9 in A549 cells. In the endoplasmic reticulum apoptosis pathway, the levels of caspase-4, ATF4, GRP78 and GADD153 were markedly upregulated. CONCLUSIONS: This study suggests that GA-13315 can be considered as a promising chemotherapeutic agent with anticancer activity in treatment of lung cancer in future.

Cutaneous metastasis from lung adenocarcinoma presenting before discovery of the primary malignancy: a case report.

Cutaneous metastasis from lung adenocarcinoma is rarer than liver, adrenal, brain, bone and other distant metastases, and the prognosis is very poor. We report a case of a 42-year-old Asian male lung adenocarcinoma patient with lymph node metastases and cutaneous metastases to the right chest wall that appeared during the comprehensive treatments, without any lesion previously found in the lung. The patient was positive for the EGFR18 exon and had an excellent tumor response to the EGFR tyrosine kinase inhibitor (EGFR-TKI) with a duration of efficacy of up to 22 months. Then, the area of right chest wall lesions expanded with ulceration, and gene detection from peripheral blood indicated that the patient acquired resistance to the administered EGFR-TKI therapy. A bilateral pleural effusion occurred 1 month later upon changing treatment to the third generation of EGFR-TKI. Then, the pleural effusion was controlled, but a change in the chest wall skin lesions was not obvious until after treatment with bevacizumab combined with cisplatin pleural perfusion. Currently, the patient is administered S-1 for maintaining treatment. Current follow-up time is more than 48 months, and the KPS score is 80 points. Through this case and a review of relevant literature, we discuss the clinical manifestations, diagnosis, treatment and prognosis of this disease and intend to provide a reference for the clinical diagnosis and treatment of similar diseases.

Deep RNA sequencing reveals the dynamic regulation of miRNA, lncRNAs, and mRNAs in osteosarcoma tumorigenesis and pulmonary metastasis.

Osteosarcoma (OS) is the most common pediatric malignant bone tumor, and occurrence of pulmonary metastasis generally causes a rapid and fatal outcome. Here we aimed to provide clues for exploring the mechanism of tumorigenesis and pulmonary metastasis for OS by comprehensive analysis of microRNA (miRNA), long non-coding RNA (lncRNA), and mRNA expression in primary OS and OS pulmonary metastasis. In this study, deep sequencing with samples from primary OS (n = 3), pulmonary metastatic OS (n = 3), and normal controls (n = 3) was conducted and differentially expressed miRNAs (DEmiRNAs), lncRNAs (DElncRNAs), and mRNAs (DEmRNAs) between primary OS and normal controls as well as pulmonary metastatic and primary OS were identified. A total of 65 DEmiRNAs, 233 DElncRNAs, and 1405 DEmRNAs were obtained between primary OS and normal controls; 48 DEmiRNAs, 50 DElncRNAs, and 307 DEmRNAs were obtained between pulmonary metastatic and primary OS. Then, the target DEmRNAs and DElncRNAs regulated by the same DEmiRNAs were searched and the OS tumorigenesis-related and OS pulmonary metastasis-related competing endogenous RNA (ceRNA) networks were constructed, respectively. Based on these ceRNA networks and Venn diagram analysis, we obtained 3 DEmiRNAs, 15 DElncRNAs, and 100 DEmRNAs, and eight target pairs including miR-223-5p/(CLSTN2, AC009951.1, LINC01705, AC090673.1), miR-378b/(ALX4, IGSF3, SULF1), and miR-323b-3p/TGFBR3 were involved in both tumorigenesis and pulmonary metastasis of OS. The TGF-ß superfamily co-receptor TGFBR3, which is regulated by miR-323b-3p, acts as a tumor suppressor in OS tumorigenesis and acts as a tumor promoter in pulmonary metastatic OS via activation of the epithelial-mesenchymal transition (EMT) program.In conclusion, the OS transcriptome (miRNA, lncRNA, and mRNA) is dynamically regulated. These analyses might provide new clues to uncover the molecular mechanisms and signaling networks that contribute to OS progression, toward patient-tailored and novel-targeted treatments.

Identification of the miRNA-mRNA regulatory network of small cell osteosarcoma based on RNA-seq.

Small cell osteosarcoma (SCO) is a rare subtype of osteosarcoma characterized by highly aggressive progression and a poor prognosis. The miRNA and mRNA expression profiles of peripheral blood mononuclear cells (PBMCs) were obtained in 3 patients with SCO and 10 healthy individuals using high-throughput RNA-sequencing. We identified 37 dysregulated miRNAs and 1636 dysregulated mRNAs in patients with SCO compared to the healthy controls. Specifically, the 37 dysregulated miRNAs consisted of 27 up-regulated miRNAs and 10 down-regulated miRNAs; the 1636 dysregulated mRNAs consisted of 555 up-regulated mRNAs and 1081 down-regulated mRNAs. The target-genes of miRNAs were predicted, and 1334 negative correlations between miRNAs and mRNAs were used to construct an miRNA-mRNA regulatory network. Dysregulated genes were significantly enriched in pathways related to cancer, mTOR signaling and cell cycle signaling. Specifically, hsa-miR-26b-5p, hsa-miR-221-3p and hsa-miR-125b-2-3p were significantly dysregulated miRNAs and exhibited a high degree of connectivity with target genes. Overall, the expression of dysregulated genes in tumor tissues and peripheral blood samples of patients with SCO measured by quantitative real-time polymerase chain reaction corroborated with our bioinformatics analyses based on the expression profiles of PBMCs from patients with SCO. Thus, hsa-miR-26b-5p, hsa-miR-221-3p and hsa-miR-125b-2-3p may be involved in SCO tumorigenesis.

Clinical effects of three surgical approaches for a giant cell tumor of the distal radius and ulna.

The aim of the present study was to assess the curative effects of three surgical approaches for a giant cell tumor (GCT) of the distal radius and ulna. A total of 27 patients with GCT on distal radius and ulnas (7 and 20, respectively), confirmed by biopsy, were treated with individualized treatment regimens, according to the Campanacci's grade system: i) Curettage plus inactivated tumor bed and allogeneic bone graft/bone cement augmentation for Campanacci's grade I GCT of the distal radius and ulna (Group A); ii) simple en bloc resection for Campanacci's grade II and III GCT of the distal ulna (Group B); iii) en bloc resection and reconstruction with non-vascularized fibular autograft/allogeneic bone graft for Campanacci's II and III GCT of the distal radius (Group C). Postoperative recurrence and complications were recorded. The Musculoskeletal Tumor Society Score was used to assess functional results. The mean follow-up time was 25 months (range, 9-125 months). A total of 3 patients exhibited tumor recurrence at 9, 11 and 15 months following surgery (1 case succumbed to pulmonary metastasis at 27 months). Overall, the incidence of the postoperative recurrence of the GCT of the distal ulna and radius were 14.3 (1/7) and 10% (2/20), respectively, with a statistical P-value of 0.762. No statistically significant difference was observed regarding the incidence of the postoperative recurrence, postoperative complications and MSTS results among the three surgical approaches for the GCT on distal ulna and radius (all P>0.05). However, statistically significant differences were noted when the incidence of the postoperative recurrence of curettage (Group A) was compared with that of en bloc resection (Groups B and C) (P=0.024). In conclusion, in order to achieve the best clinical effects for patients with GCT on distal radius and ulna, individualized treatment regimens must be designed according to the different Campanacci's grades and tumor locations.

Surgery methods and soft tissue extension are the potential risk factors of local recurrence in giant cell tumor of bone.

BACKGROUND: Various treatments of giant cell tumor of bone (GCTB) included in curettages and resections and with adjuvant are exerted, but the best treatment is controversial. The aim of the study was the identification of individual risk factors after various treatments in GCTB. METHODS: A total of 179 patients treated for GCTB between 1998 and 2010 were concluded in the retrospective study. All patients were treated with intralesional curettage, extensive curettage, or wide resection. Mean follow-up was 60.2 ± 18.7 months (36~112 months). Age, gender, tumor location, Campanacci grade, soft tissue extension, pathological features, and surgical methods were performed to univariate Kaplan-Meier survival analysis and multivariate Cox regression analysis. RESULTS: The local recurrence rates of intralesional curettage (41.9%) and extensive curettage (19.0%) were significantly higher than that of wide resection (7.7%). The higher risk of local recurrence was found for soft tissue extension (hazard = 7.921, 95% CI 1.107~56.671), compared with no statistical significances between gender, location, Campanacci grade, pathologic fracture, and local recurrences, which were shown by Kaplan-Meier analysis. However, recurrence-free survival (RFS) of patients younger than 30 was significantly lower than that of patients older than 30. The RFS of pathologic fracture patients with soft tissue extension was significantly lower than that of pathologic fracture patients without soft tissue extension. Multivariate Cox regression analysis indicated that the independent variable that contributed to recurrence-free survival was soft tissue extension and surgical methods. The RFS of extensive curettage had no statistically significant difference with wide resection and was significantly higher than that of intralesional curettage. Use of high-speed burring and bone cement significantly decreased the local recurrence rate. CONCLUSIONS: Age (below 30 years), gender, tumor location, Campanacci grade, and pathologic fracture have no statistically significant influence on local recurrences. Soft tissue extension and intralesional curettage of surgical methods increased the RFS. The results of the present study suggested that compared with curettage and wide section, treatment of GCTB by extensive curettage could provide the favorable local control and functional recovery.

Cell apoptosis, autophagy and necroptosis in osteosarcoma treatment.

Osteosarcoma is the most common primary bone tumor in children and adolescents. Although combined therapy including surgery and multi-agent chemotherapy have resulted in great improvements in the overall survival of patients, chemoresistance remains an obstacle for the treatment of osteosarcoma. Molecular targets or effective agents that are actively involved in cell death including apoptosis, autophagy and necroptosis have been studied. We summarized how these agents (novel compounds, miRNAs, or proteins) regulate apoptotic, autophagic and necroptotic pathways; and discussed the current knowledge on the role of these new agents in chemotherapy resistance in osteosarcoma.