Mononuclear infiltrates in osteosarcoma and chemokine receptor expression

Chemokines and Chemokine Receptors: Orchestrating Tumor Metastasization

Metastasis still represents the primary cause of cancer morbidity and mortality worldwide. Chemokine signalling contributes to the overall process of cancer growth and metastasis, and their expression in both primary tumors and metastatic lesions correlate with prognosis. Chemokines promote tumor metastasization by directly supporting cancer cell survival and invasion, angiogenesis, and by indirectly shaping the pre-metastatic niches and antitumor immunity. Here, we will focus on the relevant chemokine/chemokine receptor axes that have been described to drive the metastatic process. We elaborate on their role in the regulation of tumor angiogenesis and immune cell recruitment at both the primary tumor lesions and the pre-metastatic foci. Furthermore, we also discuss the advantages and limits of current pharmacological strategies developed to target chemokine networks for cancer therapy.

A complex pattern of chemokine receptor expression is seen in osteosarcoma

Background

Osteosarcoma is the most frequent bone tumor in childhood and adolescence. Patients with primary metastatic disease have a poor prognosis. It is therefore important to better characterize the biology of this tumor to define new prognostic markers or therapeutic targets for tailored therapy. Chemokines and their receptors have been shown to be involved in the development and progression of malignant tumors. They are thought to be active participants in the biology of osteosarcoma. The function of specific chemokines and their receptors is strongly associated with the biological context and microenvironment of their expression. In this report we characterized the expression of a series of chemokine receptors in the complex environment that defines osteosarcoma.

Methods

The overall level of chemokine receptor mRNA expression was determined using TaqMan RT-PCR of microdissected archival patient biopsy samples. Expression was then verified at the protein level by immunohistochemistry using a series of receptor specific antibody reagents to elucidate the cellular association of expression.

Results

Expression at the RNA level was found for most of the tested receptors. CCR1 expression was found on infiltrating mononuclear and polynuclear giant cells in the tumor. Cells associated with the lining of intratumoral vessels were shown to express CCR4. Infiltrating mononuclear cells and tumor cells both showed expression of the receptor CCR5, while CCR7 was predominantly expressed by the mononuclear infiltrate. CCR10 was only very rarely detected in few scattered infiltrating cells.

Conclusion

Our data elucidate for the first time the cellular context of chemokine receptor expression in osteosarcoma. This is an important issue for better understanding potential chemokine/chemokine receptor function in the complex biologic processes that underlie the development and progression of osteosarcoma. Our data support the suggested involvement of chemokines and their receptors in diverse aspects of the biology of osteosarcoma, but also contradict aspects of previous reports describing the expression of these receptors in this tumor.

Adult human sarcomas. I. Basic science

When connective tissue undergoes malignant transformation, glioblastomas and sarcomas arise. However, the ancient biochemical mechanisms, which are now operational in sarcomas distorted by mutations and gene fusions in misaligned chromosomes, were originally acquired by those cells that emerged during the Cambrian explosion. Preserved throughout evolution up to the genus Homo, these mechanisms dictate the apoptosis- and senescence-resistant immortality of malignant cells. A 'retroviral paradox' distinguishes human sarcomas from those of the animal world. In contrast to the retrovirally induced sarcomatous transformation of animal (avian, murine, feline and simian) cells, human sarcomas have so far failed to yield a causative retroviral isolate. However, the proto-oncogenes/oncogenes transduced from their host cells by retroviruses of animals are the same that are active in human sarcomas. Since the encoded oncoproteins arise after birth, they are recognized frequently by the immune system of the host. Immune lymphocytes that kill autologous sarcoma cells in vitro commonly fail to do so in vivo. Sarcoma vaccines generate immune T- and natural killer cell reactions; even when vaccinated patients do not show a clinical response, their tumors become more sensitive to chemotherapy. The aim of this review is to lay a solid molecular biological foundation for the conclusion that targeting the sarcoma oncogenes will result in regression of the disease.