Podocalyxin promotes proliferation and survival in mature B-cell non-Hodgkin lymphoma cells.

Podocalyxin (PCLP1) is a CD34-related sialomucin expressed by some normal cells and a variety of malignant tumors, including leukemia, and associated with the most aggressive cancers and poor clinical outcome. PCLP1 increases breast tumor growth, migration and invasion; however, its role in hematologic malignancies still remains undetermined. The purpose of this study was to investigate the expression and function of PCLP1 in mature B-cell lymphoma cells. We found that overexpression of PCLP1 significantly increases proliferation, cell-to-cell interaction, clonogenicity, and migration of B-cell lymphoma cells. Furthermore, PCLP1 overexpression results in higher resistance to death induced by dexamethasone, reactive oxygen species and type II anti-CD20 monoclonal antibody obinutuzumab. Strikingly, enforced expression of PCLP1 enhances lipid droplet formation as well as pentose phosphate pathway and glutamine dependence, indicative of metabolic reprogramming necessary to support the abnormal proliferation rate of tumor cells. Flow cytometry analysis revealed augmented levels of PCLP1 in malignant cells from some patients with mature B-cell lymphoma compared to their normal B-cell counterparts. In summary, our results demonstrate that PCLP1 contributes to proliferation and survival of mature B-cell lymphoma cells, suggesting that PCLP1 may promote lymphomagenesis and represents a therapeutic target for the treatment of B-cell lymphomas.

Podocalyxin-like protein 1 functions as an immunomodulatory molecule in breast cancer cells.

Podocalyxin-like protein 1 (PCLP1), a CD34-related sialomucin involved in the regulation of cellular morphology and adhesion, is expressed by a number of normal cells and various tumor cells. In breast malignancies PCLP1 overexpression has been associated with the most aggressive, metastatic cancers and poor prognosis. These observations suggest that PCLP1 expression could provide a mechanism to evade the immune response, thereby promoting metastatic progression of cancer. In the present work, we aimed to determine the effect of PCLP1 overexpressed in MCF7 breast cancer cells on natural killer (NK) cell cytotoxicity, dendritic cell maturation, and agonist-induced T cell proliferation. The results showed that PCLP1 expressed in MCF7 breast cancer cells confers resistance to NK cell-mediated cytolysis and impairs T cell proliferation. Furthermore, PCLP1 decreased the levels of NK cell activating receptors NKG2D, NKp30, NKp44, NKp46, DNAM-1, and CD16 on cell surface in a contact-dependent manner. Moreover, NK cells acquired PCLP1 from MCF7 cells by a process known as trogocytosis. These data reveal a new function of PCLP1 expressed on tumor cells as an immunomodulatory molecule, which may represent a mechanism to evade the immune response.

Endostatin inhibits murine colon carcinoma sinusoidal-type metastases by preferential targeting of hepatic sinusoidal endothelium.

An angiogenic response originating from peritumoral sinusoids and portal tracts that leads to the formation of metastases with sinusoidal- and portal-type angiogenic patterns, respectively, occurs during the course of liver colonization by murine 51b colon carcinoma (51b-CC) cells. We found a 5-fold increase in endogenous endostatin levels from hepatic blood over baseline (25 +/- 6 ng/mL) when micrometastatic foci had a detectable size and a 14-fold increase when macrometastases were developed. Despite this endogenous endostatin production, subcutaneous administration of recombinant human endostatin (rh-E; 50 mg/kg) decreased metastasis number by 60% when dosed from days 1 to 20 after 51b-CC cell injection, by 40% when given from days 10 to 20, and by 30% when administered as a single dose 30 minutes before 51b-CC cell injection compared with controls. In addition, administration of rh-E from days 10 to 20 decreased overall metastasis volume by 90% compared with controls. rh-E increased the number of necrotic sinusoidal-type metastases by 7-fold and decreased their intrametastatic CD31(+)-microvessel density by 80% without affecting portal-type metastases. Flow cytometry showed rh-E binding to mouse liver sinusoidal cells but not to CD45(+) cells (leukocytes and Kupffer cells) or 51b-CC cells. Furthermore, rh-E induced sinusoidal endothelium cell apoptosis. In conclusion, despite the direct correlation between metastasis development and endogenous endostatin generation in the liver, administration of rh-E inhibited micrometastasis generation and macrometastasis growth very efficiently. The antiangiogenic mechanism was selective for sinusoidal-type metastases, in which the neovasculature originating from sinusoidal endothelium cells was targeted by rh-E.