Loss of Myeloid-Specific TGF-ß Signaling Decreases CTHRC1 to Downregulate bFGF and the Development of H1993-Induced Osteolytic Bone Lesions.

The role of myeloid cell-specific TGF-ß signaling in non-small-cell lung cancer (NSCLC)-induced osteolytic bone lesion development is unknown. We used a genetically engineered mouse model, Tgfbr2LysMCre knockout (KO), which has a loss of TGF-ß signaling specifically in myeloid lineage cells, and we found that the area of H1993 cell-induced osteolytic bone lesions was decreased in Tgfbr2LysMCre KO mice, relative to the area in control littermates. The bone lesion areas were correlated with tumor cell proliferation, angiogenesis, and osteoclastogenesis in the microenvironment. The smaller bone lesion area was partially rescued by bFGF, which was expressed by osteoblasts. Interestingly, bFGF was able to rescue the osteoclastogenesis, but not the tumor cell proliferation or angiogenesis. We then focused on identifying osteoclast factors that regulate bFGF expression in osteoblasts. We found that the expression and secretion of CTHRC1 was downregulated in osteoclasts from Tgfbr2LysMCre KO mice; CTHRC1 was able to promote bFGF expression in osteoblasts, possibly through the Wnt/ß-catenin pathway. Functionally, bFGF stimulated osteoclastogenesis and inhibited osteoblastogenesis, but had no effect on H1993 cell proliferation. On the other hand, CTHRC1 promoted osteoblastogenesis and H1993 cell proliferation. Together, our data show that myeloid-specific TGF-ß signaling promoted osteolytic bone lesion development and bFGF expression in osteoblasts; that osteoclast-secreted CTHRC1 stimulated bFGF expression in osteoblasts in a paracrine manner; and that CTHRC1 and bFGF had different cell-specific functions that contributed to bone lesion development.

The growth and aggressive behavior of human osteosarcoma is regulated by a CaMKII-controlled autocrine VEGF signaling mechanism.

Osteosarcoma (OS) is a hyperproliferative malignant tumor that requires a high vascular density to maintain its large volume. Vascular Endothelial Growth Factor (VEGF) plays a crucial role in angiogenesis and acts as a paracrine and autocrine agent affecting both endothelial and tumor cells. The alpha-Ca2+/Calmodulin kinase two (α-CaMKII) protein is an important regulator of OS growth. Here, we investigate the role of α-CaMKII-induced VEGF in the growth and tumorigenicity of OS. We show that the pharmacologic and genetic inhibition of α-CaMKII results in decreases in VEGF gene expression (50%) and protein secretion (55%), while α- CaMKII overexpression increases VEGF gene expression (250%) and protein secretion (1,200%). We show that aggressive OS cells (143B) express high levels of VEGF receptor 2 (VEGFR-2) and respond to exogenous VEGF (100nm) by increasing intracellular calcium (30%). This response is ameliorated by the VEGFR inhibitor CBO-P11, suggesting that secreted VEGF results in autocrine stimulated α-CaMKII activation. Furthermore, we show that VEGF and α-CaMKII inhibition decreases the transactivation of the HIF-1α and AP-1 reporter constructs. Additionally, chromatin immunoprecipitation assay shows significantly decreased binding of HIF-1α and AP-1 to their responsive elements in the VEGF promoter. These data suggest that α-CaMKII regulates VEGF transcription by controlling HIF-1α and AP-1 transcriptional activities. Finally, CBO-P11, KN-93 (CaMKII inhibitor) and combination therapy significantly reduced tumor burden in vivo. Our results suggest that VEGF-induced OS tumor growth is controlled by CaMKII and dual therapy by CaMKII and VEGF inhibitors could be a promising therapy against this devastating adolescent disease.

Alpha-CaMKII plays a critical role in determining the aggressive behavior of human osteosarcoma.

Osteosarcoma is among the most frequently occurring primary bone tumors, primarily affecting adolescents and young adults. Despite improvements in osteosarcoma treatment, more specific molecular targets are needed as potential therapeutic options. One target of interest is α-Ca(2+)/calmodulin-dependent protein kinase II (α-CaMKII), a ubiquitous mediator of Ca(2+)-linked signaling, which has been shown to regulate tumor cell proliferation and differentiation. Here, we investigate the role of α-CaMKII in the growth and tumorigenicity of human osteosarcoma. We show that α-CaMKII is highly expressed in primary osteosarcoma tissue derived from 114 patients, and is expressed in varying levels in different human osteosarcoma (OS) cell lines [MG-63, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)/HOS, and 143B). To examine whether α-CaMKII regulates osteosarcoma tumorigenic properties, we genetically inhibited α-CaMKII in two osteosarcoma cell lines using two different α-CaMKII shRNAs delivered by lentiviral vectors and overexpressed α-CaMKII by retrovirus. The genetic deletion of α-CaMKII by short hairpin RNA (shRNA) in MG-63 and 143B cells resulted in decreased proliferation (50% and 41%), migration (22% and 25%), and invasion (95% and 90%), respectively. The overexpression of α-CaMKII in HOS cells resulted in increased proliferation (240%), migration (640%), and invasion (10,000%). Furthermore, α-CaMKII deletion in MG-63 cells significantly reduced tumor burden in vivo (65%), whereas α-CaMKII overexpression resulted in tumor formation in a previously nontumor forming osteosarcoma cell line (HOS). Our results suggest that α-CaMKII plays a critical role in determining the aggressive phenotype of osteosarcoma, and its inhibition could be an attractive therapeutic target to combat this devastating adolescent disease.