We have found that markedly elevated expression of this protein, which henceforth is referred to as secreted phosphoprotein I (Sppl) closely correlates with neoplastic transformation of a variety of cell types and that patients with advanced stage metastatic cancers have elevated levels of Sppl in their blood.
These findings indicate that OPN mRNA and proteins are expressed in human glioma cells, and that the extent of OPN expression may correlate with the malignancy grade of gliomas.
Osteopontin (OPN) is a secreted calcium-binding phosphoprotein produced in a variety of normal and pathological contexts, including tissue mineralization and cancer.
Osteopontin (OPN), an integrin-binding, transformation-associated protein, is secreted by tumor cell lines in culture and is associated with increased malignancy in some experimental tumor systems.
Increased alpha1(I) procollagen (COL) and osteopontin (OPN) mRNA expression was detected, primarily in the stromal cells, in malignant tumours compared with the benign tissue.
Osteopontin (OPN) is a secreted glycophosphoprotein which induces migration of mammary carcinoma cells, and has been implicated in the malignancy of breast carcinoma.
Moreover, a statistically significant correlation between osteopontin protein expression and advancing tumor stage was identified with the use of 303 additional specimens (human cancer = 185, adenomas = 67, and normal mucosal specimens = 51) (Spearman's rho = 0.667; P<.001).
The mRNA level of OPN, a bone matrix protein associated with enhanced malignancy, increased in non-invasive, invasive, and liver and bone metastatic breast tumor tissue compared to normal breast tissue.
Previously, we and others have shown that bone extracellular matrix proteins such as bone sialoprotein (BSP) and osteopontin (OPN) are expressed in various types of cancer that are characterized by a high affinity for bone including breast, prostate, and lung adenocarcinoma.
Osteopontin (OPN), bone sialoprotein (BSPII), and osteonectin (ON) belong to a family of glycoproteins, which have been linked to cancer metastasis and progression.
This study provides the first evidence that OPN can lead to numerous gene expression changes that influence multiple aspects of tumor progression and malignant growth.
Over time, osteopontin expressing dysplastic cells seemed to increase in number in high-grade PIN and increased further in adenocarcinoma, and in metastasis, almost all of the cancer cells immunohistochemically stained positive for osteopontin overexpression.
Furthermore, the measurement of osteopontin in the blood or tumors of patients with cancer, as a way of providing valuable prognostic information, will be discussed based on emerging clinical data.
Therefore, OPN is not merely associated with cancer, but rather it plays a multi-faceted functional role via complex molecular cross-talk with other factors.