Design BH3 domain fusion protein as targeting pro-apoptotic self-assembling nanoparticles.

Cancer is a serious global health issue, and apoptosis is a logical and practical cancer therapeutic strategy. Apoptosis responses to internal and external signals. Both BH3 domain in the pro-apoptotic proteins and truncated BH3 domain can stimulate cell apoptosis. However, the faults of peptides in systemic administration restrict the applications of truncated BH3 domain. Ferritin, as an attractive nanoparticle with the capacity of self-assemble to unique hollow spherical structure, could display truncated BH3 domain an N-terminal. Thus, in this study, we designed a pro-apoptosis self-assembling protein nanoparticle by BH3 domain fusion at N-terminal of ferritin. We evaluated the size, cytotoxicity and pro-apoptosis effect of these nanoparticles. The results showed that RGD-BH3-HFn, BH3-HFn and HFn had uniformly spherical structure with sizes at 26.08 ± 0.11 nm, 22.07 ± 0.67 nm, and 16.81 ± 0.88 nm, respectively; RGD-BH3-HFn has stronger cytotoxicity against tumor cells than BH3-HFn and HFn. The total apoptosis ratios (including necrosis) of C6 cells induced by RGD-BH3-HFn, BH3-HFn, and HFn proteins were 15.24%, 10.13% and 2.14%, respectively; those of bEnd.3 cells were 15.47%, 7.33% and 1.70%, respectively; while the total apoptosis rate (including necrosis) of MCF-7 cells were 3.24%, 4.9% and - 1.68%, respectively. The results suggested self-assembling RGD-BH3-HFn could target to C6 cells and bEnd.3 cells, and enhance tumor cells apoptosis, its apoptosis effect against C6 cells was 7.11-fold that of HFn, and apoptosis effect against bEnd.3 cells was 9.08-fold that of HFn. These results indicated BH3 domain can be designed as targeting pro-apoptotic nanoparticles.

Role of Bcl-2 in tumour cell survival and implications for pharmacotherapy.

OBJECTIVES: Bcl-2 is a protein that inhibits apoptosis, leading to cell survival. The Bcl-2 family has six different anti-apoptotic proteins, three pro-apoptotic proteins that are similar in structure, and other integrating proteins that function as promotors or inhibitors in the progression of apoptosis. In this discussion paper, we provide an overview of apoptosis, the role of Bcl-2 in normal cellular and molecular processes, and the role of Bcl-2 in tumour cell survival. It focuses primarily on anti-apoptotic Bcl-2, its activation in cancer, the manner in which it regulates the intrinsic and extrinsic mechanisms of apoptosis, and its broad molecular interactions with other critical proteins in the cell. Certain cancer treatments are reviewed and related directions for the future are presented. KEY FINDINGS: Apoptosis is common to all organisms - for eukaryotes it is a normal process of development and regeneration. The rate at which apoptosis occurs is critical to the survival of the organism, as too much can lead to the onset of degenerative diseases such as dementia, and too little may lead to cancer. FKBP-38 is a binding protein that has been discovered to be upregulated in highly aggressive cancers and binds to Bcl-2 rather than the pro-apoptotics to induce a state of hyper-mitosis. A short binding protein (Nur-77) provides new insights into Bcl-2 'masking'. Nurr-77 binds to Bcl-2 and exposes the BH3 domain, transforming it from a cancer promoter to an unorthodox cancer inhibitor. This presents in itself an interesting and exciting opportunity - increasing the rate of apoptosis in neoplastic cells that are usually protected by Bcl-2 activity at the mitochondria. SUMMARY: Development of drugs in the form of BH3-only and BH123 mimetic drugs provide a interesting avenue for cancer therapy for the future. Drugs that can either promote, or mimic anti-IAP activity such as Smac/Diablo would certainly be productive, thereby inducing apoptosis. Medicinal usage which can effectively suppress FKBP38 in Bcl-2-dependent cancers would provide further arsenal to combat apoptotic irregularities, particularly a treatment that is more dominant than kinetin riboside. WAVE-1 inhibitors may effectively suppress the phosphorylation of Bcl-2, thereby potentially reducing hyper-mitosis and increasing apoptosis. Recent findings shed molecular light on PDT, namely ER stress, and potential for anti-cancer therapy via either apoptosis or autophagy. A drug that can effectively upregulate Nurr-77, thereby masking the anti-apoptotic properties of Bcl-2, would indeed be life-saving for cancer patients.

Targeted gene therapy for breast cancer with truncated Bid.

We studied the efficiency of the proapoptotic factor tBid, targeted to tumor cells using the promoters of the hTERT, Survivin and Muc1 genes, in killing breast cancer cells. tBid is the active fragment of the proapoptotic protein Bid and is generated in response to death receptor activation. When placed under control of a strong CMV promoter, tBid was highly efficient in killing breast cancer cells. When expression of tBid was driven by tumor-specific promoters, the magnitude of killing was significant in cell lines with high levels of promoter activity. For successful gene therapy with targeted tBid, it is therefore crucial to be able to predict promoter activity prior to selection of the therapeutic construct. To test whether gene expression could serve as a predictor, we correlated expression of Survivin, hTERT and Muc1 genes with the activity of the corresponding promoters in a panel of breast cancer cell lines. Expression of the Muc1 gene correlated well with the activity of its promoter and the resultant tumor cell killing. For the hTERT and Survivin promoters, however, promoter activity did not correlate well with the expression of the corresponding genes. The implications and possible mechanism of these discrepancies are discussed.