HOXB7 expression by myeloma cells regulates their pro-angiogenic properties in multiple myeloma patients

Abstract

The deregulation of the homeobox genes as homeoboxB (HOXB)-7 has been previously associated to tumor progression and angiogenesis; here we investigated the potential role of HOXB7 in the pro-angiogenic properties of multiple myeloma (MM) cells. We found that HOXB7 was expressed in 10 out of 22 MM patients analyzed at the diagnosis related to high bone marrow angiogenesis and overexpressed in about 40% of myeloma cell lines compared with normal plasma cells. Enforced HOXB7 expression in MM cells by a lentiviral vector significantly modified their transcriptional and angiogenic profile, checked by combined microarray and angiogenesis PCR analyses, upregulating VEGFA, FGF2, MMP2, WNT5a and PDGFA and downregulating thrombospoindin-2. The pro-and anti-angiogenic HOXB7-related gene signature was also validated in a large independent dataset of MM patients. Accordingly, MM-induced vessel formation was significantly increased by HOXB7 overexpression both in vitro angiogenic and chorioallantoic membrane assays, as well as the HOXB7 silencing by small interfering RNA inhibited the production of angiogenic factors, and the pro-angiogenic properties of MM cells. Finally, in SCID-NOD mice we confirmed that HOXB7 overexpression by MM cells stimulated tumor growth, increased MM-associated angiogenesis and the expression of pro-angiogenic genes by microarray analysis supporting the critical role of HOXB7 in the angiogenic switch in MM.

Hypoxia-inducible factor (HIF)-1α suppression in myeloma cells blocks tumoral growth in vivo inhibiting angiogenesis and bone destruction

“…Recombinant lentivirus was produced by transient transfection of 293T cells following a standard protocol. HMCLs were infected as previously described 32 , and selected in culture by the presence of 4 ug per ml puromycin for 21 days. Selected clones of HMCLs were then screened for HIF-1a, HIF-1b, HIF-2a and HIF-3a mRNA and/or protein expression.…”

“…Tumor mass was measured as previously described. 32 Maximum length and width of the tumor masses were measured with a caliper, and tumor volume (mm 3 ) was calculated according to the following formula: 0.523  length  width 2 . Tumors were removed and subjected to immunohistochemical staining.…”

“…In this study, we determined the effect of stable HIF-1a inhibition in MM cells on cell proliferation and survival in vitro and growth, angiogenesis and osteolysis in vivo using plasmocytoma xenograft or intratibial mouse models previously used to evaluate the effect on myeloma cell growth and bone destruction. [32][33][34] …”

Angiogenesis and Multiple Myeloma

“…Although HIF-1α seems to be a major regulator of the proangiogenic profile of myeloma cells and MM-induced angiogenesis, more recently the potential involvement of other genes in the production of pro-angiogenic factors by myeloma cells has been elucidated [95,116].…”

The function of homeobox genes and lncRNAs in cancer

“…HOXB7 primarily regulates cell growth through the phosphoinositide 3-kinase/Akt and mitogen-activated protein kinase pathways (83). HOXB7 is able to promote cell proliferation in different types of tumors through its high levels of expression (83)(84)(85). In addition, HOXB7 has been demonstrated to be an oncogene (57,83,86,87), and its involvement is essential in various forms of cancer.…”