HTLV-1 Tax-1 interacts with SNX27 to regulate cellular localization of the HTLV-1 receptor molecule, GLUT1

An estimated 10–20 million people worldwide are infected with human T cell leukemia virus type 1 (HTLV-1), with endemic areas of infection in Japan, Australia, the Caribbean, and Africa. HTLV-1 is the causative agent of adult T cell leukemia (ATL) and HTLV-1 associated myopathy/tropic spastic paraparesis (HAM/TSP). HTLV-1 expresses several regulatory and accessory genes that function at different stages of the virus life cycle. The regulatory gene Tax-1 is required for efficient virus replication, as it drives transcription of viral gene products, and has also been demonstrated to play a key role in the pathogenesis of the virus. Several studies have identified a PDZ binding motif (PBM) at the carboxyl terminus of Tax-1 and demonstrated the importance of this domain for HTLV-1 induced cellular transformation. Using a mass spectrometry-based proteomics approach we identified sorting nexin 27 (SNX27) as a novel interacting partner of Tax-1. Further, we demonstrated that their interaction is mediated by the Tax-1 PBM and SNX27 PDZ domains. SNX27 has been shown to promote the plasma membrane localization of glucose transport 1 (GLUT1), one of the receptor molecules of the HTLV-1 virus, and the receptor molecule required for HTLV-1 fusion and entry. We postulated that Tax-1 alters GLUT1 localization via its interaction with SNX27. We demonstrate that over expression of Tax-1 in cells causes a reduction of GLUT1 on the plasma membrane. Furthermore, we show that knockdown of SNX27 results in increased virion release and decreased HTLV-1 infectivity. Collectively, we demonstrate the first known mechanism by which HTLV-1 regulates a receptor molecule post-infection.</div

Expression of parathyroid hormone-related protein during immortalization of human peripheral blood mononuclear cells by HTLV-1: Implications for transformation

<p>Abstract</p> <p>Background</p> <p>Adult T-cell leukemia/lymphoma (ATLL) is initiated by infection with human T-lymphotropic virus type-1 (HTLV-1); however, additional host factors are also required for T-cell transformation and development of ATLL. The HTLV-1 Tax protein plays an important role in the transformation of T-cells although the exact mechanisms remain unclear. Parathyroid hormone-related protein (PTHrP) plays an important role in the pathogenesis of humoral hypercalcemia of malignancy (HHM) that occurs in the majority of ATLL patients. However, PTHrP is also up-regulated in HTLV-1-carriers and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients without hypercalcemia, indicating that PTHrP is expressed before transformation of T-cells. The expression of PTHrP and the PTH/PTHrP receptor during immortalization or transformation of lymphocytes by HTLV-1 has not been investigated.</p> <p>Results</p> <p>We report that PTHrP was up-regulated during immortalization of lymphocytes from peripheral blood mononuclear cells by HTLV-1 infection in long-term co-culture assays. There was preferential utilization of the PTHrP-P2 promoter in the immortalized cells compared to the HTLV-1-transformed MT-2 cells. PTHrP expression did not correlate temporally with expression of HTLV-1 tax. HTLV-1 infection up-regulated the PTHrP receptor (PTH1R) in lymphocytes indicating a potential autocrine role for PTHrP. Furthermore, co-transfection of HTLV-1 expression plasmids and PTHrP P2/P3-promoter luciferase reporter plasmids demonstrated that HTLV-1 up-regulated PTHrP expression only mildly, indicating that other cellular factors and/or events are required for the very high PTHrP expression observed in ATLL cells. We also report that macrophage inflammatory protein-1α (MIP-1α), a cellular gene known to play an important role in the pathogenesis of HHM in ATLL patients, was highly expressed during early HTLV-1 infection indicating that, unlike PTHrP, its expression was enhanced due to activation of lymphocytes by HTLV-1 infection.</p> <p>Conclusion</p> <p>These data demonstrate that PTHrP and its receptor are up-regulated specifically during immortalization of T-lymphocytes by HTLV-1 infection and may facilitate the transformation process.</p

Canine Prostate Cancer Cell Line (Probasco) Produces Osteoblastic Metastases In Vivo

In 2012, over 240,000 men were diagnosed with prostate cancer and over 28,000 died from the disease. Animal models of prostate cancer are vital to understanding its pathogenesis and developing therapeutics. Canine models in particular are useful due to their similarities to late-stage, castration-resistant human disease with osteoblastic bone metastases. This study established and characterized a novel canine prostate cancer cell line that will contribute to the understanding of prostate cancer pathogenesis

p16, pRb, and p53 in Feline Oral Squamous Cell Carcinoma

Feline oral squamous cell carcinoma (FOSCC) is a highly aggressive head and neck cancer in cats, but the molecular pathogenesis of this cancer is still uncertain. In this study, p16, p53, and pRb proteins were detected and quantified by immunohistochemistry in forty-three FOSCC primary tumors and three FOSCC xenografts. p16 mRNA levels were also measured in three FOSCC cell lines (SCCF1, F2, and F3), which were consistent with their p16 immunoreactivity. Feline SCCF1 cells had very high levels of p16 protein and mRNA (55-fold greater) compared to SCCF2 and F3. A partial feline p16 cDNA sequence was amplified and sequenced. The average age of cats with FOSCC with high p16 immunoreactivity was significantly lower than the average age in the low p16 group. Eighteen of 43 (42%) FOSCCs had low p16 intensity, while 6/43 (14%) had high p16 immunoreactivity. Feline papillomavirus L1 (major capsid) DNA was not detected in the SCC cell lines or the FOSCCs with high p16 immunostaining. Five of 6 (83%) of the high p16 FOSCC had low p53, but only 1/6 (17%) had low pRb immunoreactivity. In summary, the staining pattern of p16, p53, and pRb in FOSCC was different from human head and neck squamous cell carcinoma and feline cutaneous squamous cell carcinoma. The majority of FOSCCs have low p16 immunostaining intensity, therefore, inactivation of CDKN2A is suspected to play a role in the pathogenesis of FOSCC. A subset of FOSCCs had increased p16 protein, which supports an alternate pathogenesis of cancer in these cats

CD147 and Cyclooxygenase Expression in Feline Oral Squamous Cell Carcinoma

Feline oral squamous cell carcinoma (OSCC) is a highly invasive form of cancer in cats. In human OSCC, cluster of differentiation 147 (CD147) contributes to inflammation and tumor invasiveness. CD147 is a potential therapeutic target, but the expression of CD147 in feline OSCC has not been examined. Immunohistochemistry was used to determine if cyclooxygenase 2 (COX-2) and CD147 expression in feline OSCC biopsies was coordinated. Tumor cells were more likely to express COX-2 (22/43 cases or 51%) compared to stroma (8/43 or 19%) and adjacent oral epithelium (9/31 cases or 29%) (p &lt; 0.05). CD147 was also more likely to occur in tumor cells compared to stroma and adjacent mucosa, with 21/43 (49%) of cases having &gt;50% tumor cells with mild or moderate CD147 expression, compared to 9/28 (32%) in adjacent epithelium and only 5/43 (12%) in adjacent stroma (p &lt; 0.05). In feline OSCC cell lines (SCCF1, SCCF2, and SCCF3), CD147 gene expression was more consistently expressed compared to COX-2, which was 60-fold higher in SCCF2 cells compared to SCCF1 cells (p &lt; 0.05). CD147 expression did not correlate with COX-2 expression and prostaglandin E2 (PGE2) secretion, indicating that they may be independently regulated. CD147 potentially represents a novel therapeutic target for the treatment of feline OSCC and further study of CD147 is warranted

The Calcium-Sensing Receptor Is Necessary for the Rapid Development of Hypercalcemia in Human Lung Squamous Cell Carcinoma

The calcium-sensing receptor (CaR) is responsible for the regulation of extracellular calcium (Ca2+o) homeostasis. CaR activation has been shown to increase proliferation in several cancer cell lines; however, its presence or function has never been documented in lung cancer. We report that Ca2+o-activated CaR results in MAPK-mediated stimulation of parathyroid hormone-related protein (PTHrP) production in human lung squamous cell carcinoma (SCC) lines and humoral hypercalcemia of malignancy (HHM) in vivo. Furthermore, a single nucleotide polymorphism in CaR identified from a hypercalcemia-inducing lung SCC reduced the receptor's activation threshold leading to increased PTHrP expression and secretion. Increasing the expression of either wild-type CaR or a CaR variant with a single nucleotide polymorphism in the cytoplasmic domain was both necessary and sufficient for lung SCC to induce HHM. Because lung cancer patients who frequently develop HHM and PTHrP expression in lung cancer has been only partially explained, the significance of our findings indicates that CaR variants may provide a positive feedback between PTHrP and calcium and result in the syndrome of HHM

Deletion of the nuclear localization sequence and C-terminus of parathyroid hormone–related protein decreases osteogenesis and chondrogenesis but increases adipogenesis and myogenesis in murine bone marrow stromal cells

The N-terminus of parathyroid hormone–related protein regulates bone marrow stromal cell differentiation. We hypothesized that the nuclear localization sequence and C-terminus are involved. MicroRNA and gene expression analyses were performed on bone marrow stromal cells from mice lacking the nuclear localization sequence and C-terminus ( Pthrp Δ/Δ ) and age-matched controls. Differentiation assays with microRNA, cytochemical/histologic/morphologic, protein, and gene expression analyses were performed. Pthrp Δ/Δ bone marrow stromal cells are anti-osteochondrogenic, pro-adipogenic, and pro-myogenic, expressing more Klf4 , Gsk-3β , Lif , Ct-1 , and microRNA-434 but less β-catenin , Igf-1 , Taz , Osm , and microRNA-22 ( p  ⩽ 0.024). Pthrp Δ/Δ osteoblasts had less mineralization, osteocalcin, Runx2 , Osx , Igf-1 , and leptin ( p  ⩽ 0.029). Pthrp Δ/Δ produced more adipocytes, Pparγ , and aP2 , but less Lpl ( p  ⩽ 0.042). Pthrp Δ/Δ cartilage pellets were smaller with less Sox9 and Pth1r , but greater Col2a1 ( p  ⩽ 0.024). Pthrp Δ/Δ produced more myocytes, Des , and Myog ( p  ⩽ 0.021). MicroRNA changes supported these findings. In conclusion, the nuclear localization sequence and C-terminus are pro-osteochondrogenic, anti-adipogenic, and anti-myogenic