Department of Biochemistry

Background/Objectives: Osteosarcoma is an aggressive bone malignancy with high metastatic potential to the lungs. CTCs, as seeds of metastasis, play an important role in the spread of this cancer, and, therefore, their isolation, culture, and gene expression analysis promises valuable insights into the progression and metastatic cascade of osteosarcoma. The aim of this study was to isolate and culture CTCs from osteosarcoma-bearing mice and compare their migration, radioresistance, and gene expression with their parental cell line. Methods: CTCs from LM8-inoculated mice were isolated and cultured. The gene expression of the CTC-derived cell lines was then compared to the parental cell line. Furthermore, a Transwell assay, a clonogenic assay after irradiation, and immunohistochemical stainings were used to compare the CTC-derived cell lines with the parental cell line. Results: The CTC-derived cell lines differed significantly in gene expression from their parental cell line. 361 differentially expressed genes were identified, among which GO and KEGG analysis revealed major differences in the expression of genes related to antigen processing and presentation and extracellular matrix constituents. In addition, the CTC-derived cell lines were observed to have a higher migratory capacity and comparable radioresistance compared to the parental cell line. CD44 expression was found to be conserved in CTC-derived cell lines. Conclusions: This study provides a comparison between CTC-derived and their parental cell lines in terms of gene expression, migration, and radioresistance. Our findings allow for further research in the field of osteosarcoma CTCs and their generation. Furthermore, the identified DEGs between CTCs and their parental cell line can serve as a reference point for targeted therapies against osteosarcoma CTCs.

The cancer chemotherapy regimen of a taxane and platinum combination was developed more than forty years ago, yet remains the cornerstone of treatment for several major cancer types today. Although many new agents targeting cancer genes and pathways have been developed and evaluated, none have been sufficient to replace the long-established taxane/platinum combination. This leads us to ponder why, after four decades of colossal efforts, multiple discoveries, and tremendous advances in understanding gene mutations and biology, the development of conceptually superior targeted therapies has not yet achieved overwhelming success in replacing cytotoxic chemotherapy. The concept of targeted therapy is based on the idea that blocking the altered pathway(s) crucial for cancer development (and maintenance), the disturbance in cellular signaling, metabolism, and functions will make the targeted cancer cells unfit and trigger programmed cell death in cancer cells, but without the significant side effects that limit chemotherapy. We propose that the lack of anticipated triumphs of targeted therapy stems from the desensitization of programmed cell death pathways during neoplastic transformation and malignant progression of cancer cells. This renders the targeting drugs largely ineffective at killing cancer cells and mostly insufficient in clinical implements. Recent advances in understanding suggest that, in contrast to targeted therapies, taxanes and platinum agents kill cancer cells by physical rupturing nuclear membranes rather than triggering apoptosis, making their effect independent of the intrinsic cellular programmed cell death mechanism. This new recognition of the non-programmed cell death mechanism in the success of chemotherapeutic agents, such as taxanes and platinum, may inspire oncologists and cancer researchers to focus their efforts more productively on developing effective non-programmed cell death cancer therapies to replace or significantly improve the application of the current standard taxane/platinum regimens.