Studies of the anticancer effect of calcineurin B

Cytotoxic Effect of Trypanosoma cruzi Calcineurin B Against Melanoma and Adenocarcinoma Cells In Vitro

Chagas disease caused by the obligate intracellular flagellate protozoan Trypanozoma cruzi infects about 6 million people. From the 1930s to the present, the antitumor capacity of T. cruzi has been studied; however, the identification of the responsible molecules for this effect remains undiscovered. Calcineurin, a calcium/calmodulin-dependent serine/threonine phosphatase, is a heterodimer consisting of a catalytic subunit (CaNA) and a regulatory subunit (CaNB). It has been described that T. cruzi CaN is involved in the cell invasion and proliferation of the parasite. Recently, extracellular human CaNB has been demonstrated to be capable of inhibiting tumor growth cells, conferring an antitumor effect; however, the extracellular role of T. cruzi CaNB (TcCaNB) is still unknown. The objective of this work was to investigate the antitumor potential of TcCaNB by interacting with membrane proteins and evaluating its effects on the viability, proliferation, and morphology of tumor cells in vitro. Additionally, the possible mechanism of action of TcCaNB was explored. Murine melanoma (B16-F10), human cervical adenocarcinoma (HeLa), and African green monkey kidney epithelial (Vero) cell lines were employed for in vitro assays. Far Western blot and immunofluorescence were performed to assess the interaction of TcCaNB with membrane proteins, and the effect of TcCaNB on cell viability and proliferation was evaluated using the MTS assay and the CyQUANT NF assay, respectively. The effect of the caspase inhibitor Z-VAD-FMK on TcCaNB-stimulated tumor cells was investigated to determine if TcCaNB-induced cell death was associated with apoptosis. To assess cell cycle progression, TcCaNB-treated cells were analyzed by flow cytometry. In this study, the results showed an interaction of TcCaNB with cell membrane proteins in B16-F10 and HeLa tumor lines, indicating that TcCaNB is capable of decreasing viability and proliferation of B16-F10 and HeLa cells, with no significant effect observed in Vero cells. Furthermore, morphological changes were observed in tumor cells treated with TcCaNB. DNA fragmentations and inhibition of caspases with Z-VAD-FMK partially counteracted the cytotoxic effects of TcCaNB on tumor cells, suggesting that TcCaNB-induced cell death might be associated with apoptosis. Additionally, TcCaNB caused S phase cell cycle arrest in HeLa cells, with an increase in the sub-G1 population indicative of apoptosis, while no significant effects were observed in Vero cells.

Calcineurin subunit B is involved in shell regeneration in Haliotis diversicolor

Abalone shells are mainly composed of two major polymorphs of CaCO₃ that are distributed in different layers of the shell. The process of shell biomineralization is controlled by genes and proteins expressed within the mantle epithelium. In this present paper, we conducted a shell regeneration experiment to study the role of HcCNA and HcCNB (individual subunits of calcineurin) in shell biomineralization in H. diversicolor. The results of qPCR showed that HcCNB is upregulated to a greater extent than HcCNA in the mantle after shell notching. In vivo study of the effects of rHcCNB injection showed a significantly higher percentage of regenerated shell length, but not area, in the injected group compared to the control group. In addition, SEM observation of the inner surface of the regenerated shells revealed three different zones including prismatic, nacreous, and a distinct transition zone. Changes in the crystal organization and ultrastructure are clearly evident in these three zones, particularly after 3 weeks of rHcCNB administration. We hypothesize that this is due to faster biomineralization rates in the rHcCNB treated group. Taken together, our results demonstrate that HcCNB participates in shell regeneration in H. diversicolor. As calcineurin subunits have also been implicated in shell formation in bivalves, these findings suggest that calcineurin subunits may play important roles in biomineralization in all conchiferans.

The immunostimulatory effects and pro-apoptotic activity of rhCNB against Lewis lung cancer is mediated by Toll-like receptor 4

Background

Recombinant human calcineurin B subunit (rhCNB) has been shown to be an immune‐stimulatory protein promoting cytokine production and inducing phenotypic maturation of Dendritic cells (DCs). In vivo, it has good antitumor efficacy, and has potential as an antitumor drug. Exogenous rhCNB was found to be internalized into tumor cells via the Toll‐like receptor 4 (TLR4) complex, but it was not known whether its immuno‐modulatory and antitumor functions involved entry by this same route.

Methods

The production and secretion of the cytokines and chemokines in innate immune cells induced by rhCNB were determined by ELISA, and the expression of CD40, CD80, CD86, and MHCII was analyzed by FACs. Experimental Lewis lung cancer (LLC) model was prepared in C57 BL/6 wild‐type (WT) mice, TLR4^−/− mice or their littermates by the inoculation of LLCs in their right armpit, and then administrated daily intraperitoneal injections (0.2 mL) of normal saline, rhCNB 20 mg/kg, and rhCNB 40 mg/kg, respectively.

Results

Recombinant human calcineurin B subunit promoted the production of antitumor cytokines by innate immune cells, and culture supernatants of rhCNB‐stimulated immune cells induced apoptosis of LLCs. In addition, rhCNB up‐regulated CD40, CD80, CD86, and MHCII expression in macrophages and DCs in TLR4⁺ cells but failed to do so in TLR4 deficient cells. rhCNB also induced the formation of CD4⁺ and CD8⁺T cells in splenocytes from WT mice, but not from TLR4‐deficient littermates. Intraperitoneal administration of WT C57BL/6 mice with rhCNB resulted in a 50% reduction in LLC tumor growth, but failed to inhibit tumor growth in TLR4^−/− littermates.

Conclusions

The in vivo antitumor and immunomodulatory effects of rhCNB are mediated by the TLR4. This conclusion is important for the further understanding and development of rhCNB as an antitumor drug.

Identification of a targeting-delivery peptide based on rhCNB

Calcineurin B subunit (CNB) is the regulatory subunit of calcineurin (CN), and its classical function is to regulate the activity of CN. Research in our laboratory has revealed that the recombinant human CNB (rhCNB) is a good antitumor candidate and can be internalized by tumor cells via TLR4 receptor complexes and targeted to tumor tissue in nude mice. However, the fragment or domain of rhCNB mediating internalization and target delivery has not been identified. To explore fragment- mediated rhCNB internalization and target delivery, we generated truncated derivatives of rhCNBs by recombinant DNA technology and examined their cellular uptake. Interactions between truncated rhCNBs and the TLR4 receptor were studied by ELISA and co-immunoprecipitation, and targeting of model tumors in nude mice was examined. The results showed that one truncated derivative, Trun3 (124-169aa), was taken up by cells and targeted tumors with almost the same efficiency as intact rhCNB. These results indicate that Trun3 (45aa) contains the major sequence responsible for rhCNB internalization and tumor targeting and might be developed for drug delivery to tumors.

Hypercalcaemia in a Patient with 2p13.2-p16.1 Duplication

BACKGROUND

Partial duplication of 2p is a rare condition that causes facial anomalies, psychomotor delay, and growth failure. Hypercalcaemia is rare in children. So far, duplication of 2p has never been associated with hypercalcaemia.

METHODS

Here, we report a girl with a partial duplication of 2p presenting with moderate to severe hypercalcaemia at the age of 2 years. She also had hypercalciuria, nephrocalcinosis, decreased renal function, and secondary hyperparathyroidism at presentation. She was thoroughly investigated, including genetic testing of the CYP24A1, CASR, ALPL, and NOD2 genes, to determine the cause of hypercalcaemia.

RESULTS

1,25-dihydroxyvitamin D levels were increased. Hypercalcaemia and hypercalciuria responded well to glucocorticoids but not to cinacalcet. Hyperparathyroidism resolved with improving renal function. Apart from the known duplication of 2p, no pathogenic variants were detected in the studied genes. The duplication of 2p contains the PPP3R1 gene, which encodes for the calcineurin B subunit.

CONCLUSION

We conclude that partial duplication of 2p can be associated with hypercalcaemia and hypercalciuria and hypothesise that the underlying mechanism is an increased extra-renal, parathyroid hormone-independent 25-hydroxyvitamin D 1α-hydroxylase activity, leading to raised amounts of 1,25-dihydroxyvitamin D. The increased enzymatic activity could possibly be caused by calcineurin B subunit-related macrophage stimulation.

Cellular uptake of exogenous calcineurin B is dependent on TLR4/MD2/CD14 complexes, and CnB is an endogenous ligand of TLR4

Our previous research showed that recombinant calcineurin B (rhCnB) stimulates cytokine secretion by immune cells, probably through TLR4. Exogenous CnB can be incorporated into many different tumour cells in vitro, but the mode of uptake and receptors required remain unknown. Here, we report that exogenous CnB is taken up by cells in a time- and concentration-dependent manner via clathrin-dependent receptor-mediated internalization. Our findings further confirm that uptake is mediated by the TLR4/MD2 complex together with the co-receptor CD14. The MST results revealed a high affinity between CnB and the TLR4 receptor complex. No binding was detected between CnB and LPS. CnB inhibited the uptake of LPS, and LPS also inhibited the uptake of CnB. These results indicate that the uptake of exogenous CnB did not occur through LPS and that CnB was not a chaperone of LPS. Thus, we conclude that TLR4 receptor complexes were required for the recognition and internalization of exogenous CnB. CnB could be a potential endogenous ligand of TLR4 and function as an agonist of TLR4. These properties of CnB support its potential for development as an anti-cancer drug.

Quality-control method for the determination of biological activity of engineered calcineurin subunit B

The aim of this study was to establish a quality-control method for calcineurin subunit B (CNB) biological activity determinations. CNB enhances the p-nitrophenylphosphate (pNPP) dephosphorylating activity of calcineurin subunit A Δ316 mutant (CNAΔ316). A series of CNB concentrations were fitted to a four-parameter equation to calculate the corresponding pNPP maximum dephosphorylation rates. Values were calculated based on biological activity references using a parallel line method. The method was then validated for accuracy, precision, linearity, linear range, sensitivity, specificity, and robustness. The recovery results were greater than 98%. Intra-plate precision was 6.7%, with inter-plate precision of 10.8%. The coefficient of determination was greater than 0.98. The linear range was 0.05-50 μg mL(-1), with sensitivity of 50 μg mL(-1). Tested cytokines did not induce CNAΔ316 dephosphorylation of pNPP. The chosen CNAΔ316 concentration range did not affect activity determinations.

Calcineurin subunit B upregulates β-interferon production by phosphorylation of interferon regulatory factor 3 via Toll-like receptor 4

Toll-like receptors (TLRs) function as pattern-reorganization receptors in mammals and play an essential role in innate immunity. After recognizing certain ligands, TLRs activate a cascade of signal pathways to establish a guard environment. For the first time, we report that in vitro treatment with recombinant calcineurin subunit B (CNB) upregulated several TLR-related genes. Calcineurin subunit B interacted with the ectodomain of TLR4 in vitro. On further investigation, phosphorylation of interferon regulatory factor 3 and degradation of IκB-α were observed by CNB stimulation. In addition to pro-inflammatory cytokines, transcription and production of β-interferon were also enhanced after CNB stimulation. Thus, CNB could be further explored as a cancer and virus immunotherapy drug.

Calcineurin B subunit interacts with proteasome subunit alpha type 7 and represses hypoxia-inducible factor-1α activity via the proteasome pathway

The calcineurin (CN) B subunit (CNB) is the regulatory subunit of CN, which is the only serine/threonine-specific protein phosphatase regulated by Ca2+/CaM. It has been shown to have potential as an anticancer agent, and has a positive effect on the phagocytic index and coefficient. We report here that CNB binds to proteasome subunit alpha type 7 (PSMA7) and inhibits the transactivation activity of hypoxia-inducible factor-1α (HIF-1α) via the proteasome pathway. In addition, we show that CNB represses the expression of vascular endothelial growth factor (VEGF), which is regulated by HIF-1α. These results indicate that CNB modulates cellular proteasome activity via a specific interaction with PSMA7. This may provide a molecular basis for its anticancer and antiviral activities.

Overexpression of calcineurin B subunit (CnB) enhances the oncogenic potential of HEK293 cells

Calcineurin (CaN) is a Ca(2+)/calmodulin (CaM)-stimulated protein phosphatase. It is a heterodimeric enzyme consisting of a catalytic A subunit (CnA) and a Ca(2+)-binding regulatory B subunit (CnB). CaN's key role in vivo is well known, while the function of CnB keeps unclear except that it acts as a regulator of CaN. The present paper shows that CnB overexpression promotes proliferation of human embryonic kidney HEK293 cells by comparing with vector control cells in the complete or serum reduced medium. Furthermore, stable CnB transfectants showed dramatically improved growth in soft agar. And the migration ability of CnB overexpressors also was enhanced remarkably. But in the progress of transformation, the activity of CaN remained unchanged between CnB overexpressors and controls. Therefore, CnB, rather than CaN, is involved in the proliferation promotion of HEK293 cells. Subsequently, 11 proteins with different expression levels between CnB transfectants and controls were identified using two-dimensional gel electrophoresis and electrospray ionization time-of-fight mass spectrometry. Therein, the expression of heat shock protein 27 (HSP27) and protein DJ-1 increased along with CnB overexpression. The important role of CnB in cell neoplastic transformation was found and the possible mechanism was analyzed.