Proteomic Identification of Haptoglobin α2 as a Glioblastoma Serum Biomarker: Implications in Cancer Cell Migration and Tumor Growth

Abstract

Glioblastoma (GBM; grade IV astrocytoma) is the most malignant and common primary brain tumor in adults. Using combination of 2-DE and MALDI-TOF MS, we analyzed 14 GBM and 6 normal control sera and identified haptoglobin α2 chain as an up-regulated serum protein in GBM patients. GBM-specific up-regulation was confirmed by ELISA based quantitation of haptoglobin (Hp) in the serum of 99 GBM patients as against lower grades (49 grade III/AA; 26 grade II/DA) and 26 normal individuals (p = 0.0001). Further validation using RT-qPCR on an independent set (n = 78) of tumor and normal brain (n = 4) samples and immunohistochemcial staining on a subset (n = 42) of above samples showed increasing levels of transcript and protein with tumor grade and were highest in GBM (p = <0.0001 and <0.0001, respectively). Overexpression of Hp either by stable integration of Hp cDNA or exogenous addition of purified Hp to immortalized astrocytes resulted in increased cell migration. RNAi-mediated silencing of Hp in glioma cells decreased cell migration. Further, we demonstrate that both human glioma and mouse melanoma cells overexpressing Hp showed increased tumor growth. Thus, we have identified haptoglobin as a GBM-specific serum marker with a role on glioma tumor growth and migration.

Hypoxia-inducible Factor-1α Enhances Haptoglobin Gene Expression by Improving Binding of STAT3 to the Promoter

“…Based on the results of our study, it is possible that, in the tumor microenvironment containing abundant active STAT3 and HIF-1␣, Hp can be effectively expressed via the synergistic actions of the two transcription factors and contributes to the enhanced levels in cancer. In fact, we (43) and others (42) have reported the Hp production in reactive astrocytes after transient forebrain ischemia and in human glioblastoma cells, respectively.…”

“…A very recent study demonstrated that Hp plays an important role in the migration of human glioblastoma cells (42), an aggressive brain tumor, and HIF-1␣, as well as STAT3, is required for the tumor development (41,44,45). Furthermore, in a tumor xenograft model, mouse-implanted Hp-overexpressing glioma cells showed increased tumor growth and a decreased survival rate (42). Our study supports the possibility that Hp may be up-regulated locally in cancer environments providing active STAT3 and hypoxia and participate in angiogenesis and cell migration, which promote tumor growth and invasion.…”

Elevated Serum Haptoglobin is Associated with Clinical Outcome in Triple-Negative Breast Cancer Patients

“…In humans, the HP locus is polymorphic, with two codominant alleles (HP1 and HP2) that yield three distinct genotypes/phenotypes (Hp1-1, Hp2-1 and Hp2-2) (Sadrzadeh and Bozorgmehr, 2004). Elevated levels of haptoglobin have been demonstrated in lung cancer (Beckman et al, 1986), bladder cancer (Benkmann et al, 1987), leukemia (Mitchell et al, 1988), breast cancer (Awadallah and Atoum, 2004), malignant lymphoma (Epelbaum et al, 1998), urogenital tumors (Dunzendorfer et al, 1980), esophageal squamous cell carcinoma , ovarian cancer (Zhao et al, 2007) and gliomas (Kumar et al, 2010).…”

The Quantitative Levels of Serum Brca1, Total Protein, Albumin, and Serum Protein Electrophoresis Pattern as a Novel Biomarkers of Breast Cancer Correlating in the Familial Breast Cancer Patients in Iraq.

“…[26,27] In regarded to serum beta; transferrin and beta-lipoprotein (LDL) comprises the beta-1, increased beta-1 protein due to the increased level of free transferrin is typical of iron deficiency anemia, pregnancy, and estrogen therapy. [28] Serum lipoprotein metabolism was regulated and controlled by the specific apolipoprotein (Apo-) constituents of the various lipoprotein classes such as ApoAI, ApoCI, ApoH (beta2 glycoprotein).…”