Inducing apoptosis of human colon cancer cells by an IGF-I D domain analogue peptide

Elucidating the potential of Annona muricata L. grown in Sri Lanka to be used in developing an anticancer drug against colorectal and breast cancers

BACKGROUND

Since ancient times many traditional medicine systems around the world have been using different parts of Annona muricata L. (AM), to treat cancer. Indeed, numerous in vitro and in vivo studies also have shown anticancer properties of different solvent extracts of different parts of AM. Even the same part of the plant has shown different levels of anticancer properties based on geographical variations. Therefore, in the present study, the anticancer potential of the leaves, fruit pulp and the fruit peel of the AM that is grown in Sri Lanka was comparatively analyzed with the intention of identifying the most suitable part to be developed into a nutraceutical with anticancer effects.

METHODS

Freeze-dried aqueous extracts of immature leaves (ILAM), mature leaves (MLAM), pulp (PAM) and peel (PLAM) of AM were analyzed for their antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and 2,2-azinobis-3-ethylbenzothiozoline-6-sulfonic acid (ABTS) cation decolorization assays. Their cytotoxicity on breast cancer (MCF-7) cells, colorectal adenocarcinoma (DLD-1) cells and normal human gingival fibroblasts (HGF-1) were determined by the 3-(4,5- dimethylthiazole-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) assay. Their effect on mRNA expression of proapoptotic (Bax and caspase-7) and cell cycle arresting (p21) genes was analyzed by RT- qPCR in the same cell lines.

RESULTS

ILAM demonstrated the highest antioxidant activity in both DPPH and ABTS assays followed by MLAM, PLAM and PAM. In the MTT assay, both ILAM and MLAM demonstrated strong cytotoxic activity against MCF-7 and DLD-1 cell lines while there were no cytotoxic effects on the normal human cell line HGF-1. Both ILAM and MLAM demonstrated concentration-dependent upregulation of mRNA expression of cell cycle arresting gene p21 and apoptosis inducing genes Bax and caspase-7 in MCF-7 and DLD-1 cells.

CONCLUSION

The AEAM leaves grown in Sri Lanka has significantly higher antioxidant activity as well as selective cytotoxic effects on MCF-7 and DLD-1 cancer cells compared to its PL and P counterparts. Further, the AEAM leaves induced mRNA expression of the anticancer genes p21, Bax and caspase-7, indicating its potential to be developed into an anticancer drug against breast and colorectal cancer.

Effects of cerebrolysin on rat Schwann cells in vitro

Although the peripheral nervous system (PNS) is capable of regeneration, these processes are limited. As a potential means to augment PNS regeneration, the effects of cerebrolysin (CL), a proteolytic peptide fraction, were tested in vitro on Schwann cell (SC) proliferation, stress resistance, phagocytic and cluster-forming capacity. Primary SC/fibrocyte co-cultures were prepared from dorsal root ganglia of 5-7-day-old rats. SCs were subjected to mechanical stress by media change and metabolic stress by serum glucose deprivation (SGD). Cell survival was assessed using MTT test. SC proliferation was determined by counting BrdU-labeled cells. SC clustering was studied by ImageJ analysis of S100 immunostaining. Wallerian degeneration (WD) was evaluated by measuring acetylcholine-esterase staining within sciatic nerves in vitro. It was found that CL caused no effect on MTT turnover in the tested doses. CL inhibited SC proliferation in a dose-dependent manner. Media change and additional SGD stress inhibited SC clustering. CL enhanced the reorganization of SC clusters and was able to counteract SGD-induced cluster defects. Moreover, CL accelerated WD in vitro. CL was able to enhance the functions of SCs that are relevant to nerve regeneration. Thus, our findings suggest that CL may be suitable for therapeutic usage to enhance PNS regeneration/reconstruction.

Ubiquitin-like (UBX)-domain-containing protein, UBXN2A, promotes cell death by interfering with the p53-Mortalin interactions in colon cancer cells

Mortalin (mot-2) induces inactivation of the tumor suppressor p53's transcriptional and apoptotic functions by cytoplasmic sequestration of p53 in select cancers. The mot-2-dependent cytoprotective function enables cancer cells to support malignant transformation. Abrogating the p53-mot-2 interaction can control or slow down the growth of cancer cells. In this study, we report the discovery of a ubiquitin-like (UBX)-domain-containing protein, UBXN2A, which binds to mot-2 and consequently inhibits the binding between mot-2 and p53. Genetic analysis showed that UBXN2A binds to mot-2's substrate binding domain, and it partly overlaps p53's binding site indicating UBXN2A and p53 likely bind to mot-2 competitively. By binding to mot-2, UBXN2A releases p53 from cytosolic sequestration, rescuing the tumor suppressor functions of p53. Biochemical analysis and functional assays showed that the overexpression of UBXN2A and the functional consequences of unsequestered p53 trigger p53-dependent apoptosis. Cells expressing shRNA against UBXN2A showed the opposite effect of that seen with UBXN2A overexpression. The expression of UBXN2A and its apoptotic effects were not observed in normal colonic epithelial cells and p53-/- colon cancer cells. Finally, significant reduction in tumor volume in a xenograft mouse model in response to UBXN2A expression was verified in vivo. Our results introduce UBXN2A as a home defense response protein, which can reconstitute inactive p53-dependent apoptotic pathways. Inhibition of mot-2-p53 interaction by UBXN2A is an attractive therapeutic strategy in mot-2-elevated tumors.

α6 integrin transactivates insulin-like growth factor receptor-1 (IGF-1R) to regulate caspase-3-mediated lens epithelial cell differentiation initiation

The canonical mitochondrial death pathway was first discovered for its role in signaling apoptosis. It has since been found to have a requisite function in differentiation initiation in many cell types including the lens through low level activation of the caspase-3 protease. The ability of this pathway to function as a molecular switch in lens differentiation depends on the concurrent induction of survival molecules in the Bcl-2 and IAP families, induced downstream of an IGF-1R/NFκB coordinate survival signal, to regulate caspase-3 activity. Here we investigated whether α6 integrin signals upstream to this IGF-1R-mediated survival-linked differentiation signal. Our findings show that IGF-1R is recruited to and activated specifically in α6 integrin receptor signaling complexes in the lens equatorial region, where lens epithelial cells initiate their differentiation program. In studies with both α6 integrin knock-out mice lenses and primary lens cell cultures following α6 integrin siRNA knockdown, we show that IGF-1R activation is dependent on α6 integrin and that this transactivation requires Src kinase activity. In addition, without α6 integrin, activation and expression of NFκB was diminished, and expression of Bcl-2 and IAP family members were down-regulated, resulting in high levels of caspase-3 activation. As a result, a number of hallmarks of lens differentiation failed to be induced; including nuclear translocation of Prox1 in the differentiation initiation zone and apoptosis was promoted. We conclude that α6 integrin is an essential upstream regulator of the IGF-1R survival pathway that regulates the activity level of caspase-3 for it to signal differentiation initiation of lens epithelial cells.

Multiple applications of Alamar Blue as an indicator of metabolic function and cellular health in cell viability bioassays

Accurate prediction of the adverse effects of test compounds on living systems, detection of toxic thresholds, and expansion of experimental data sets to include multiple toxicity end-point analysis are required for any robust screening regime. Alamar Blue is an important redox indicator that is used to evaluate metabolic function and cellular health. The Alamar Blue bioassay has been utilized over the past 50 years to assess cell viability and cytotoxicity in a range of biological and environmental systems and in a number of cell types including bacteria, yeast, fungi, protozoa and cultured mammalian and piscine cells. It offers several advantages over other metabolic indicators and other cytotoxicity assays. However, as with any bioassay, suitability must be determined for each application and cell model. This review seeks to highlight many of the important considerations involved in assay use and design in addition to the potential pitfalls.

The igf system in carcinogenesis and its implication for cancer therapy

The discovery of the insulin-like growth factor (igf) system occurred half a century ago, in a series of experiments showing that the growth hormone itself exercises no direct metabolic action on skeletal tissues, but rather acts through secondary substances[...].

Pretreatment with insulin-like growth factor I protects skeletal muscle cells against oxidative damage via PI3K/Akt and ERK1/2 MAPK pathways

Oxidative stress has an important role in the pathogenesis of many muscle diseases. The major contributors to oxidative stress in muscle tissue are reactive oxygen species such as oxygen ions, free radicals, and peroxides. Insulin-like growth factor I (IGF-I) has been shown to increase muscle mass and promote muscle cell proliferation, differentiation, and survival. We, therefore, hypothesized that IGF-I might also be cytoprotective for muscle cells during oxidative stress. Exogenous hydrogen peroxide (H(2)O(2)) was used to induce oxidative stress/damage in two types of skeletal muscle cells. Apoptotic pathways were assessed after the oxidative damage and the effects of IGF-I on oxidative stress in muscle cells were examined. Different IGF-I sub-pathways were analyzed with measurement of the expression of pro-and anti-apoptotic proteins. It was found that H(2)O(2) diminishes muscle cell viability and induces a caspase-independent apoptotic cell death. Pretreatment with IGF-I protects muscle cells from H(2)O(2)-induced cell death and enhances muscle cells survival. This effect appears to result from the promotion of the anti-apoptotic protein, Bcl2. Further investigation shows that protection is via an IGF-I sub-pathway: PI3K/Akt and ERK1/2 MAPK pathways. Protecting muscle cells from oxidative damage presents a potential application in the treatment of the muscle wasting, which appears in many muscle pathologies including Duchenne muscle dystrophy and sarcopenia.

The role of insulin-like growth factors (IGF) in cell division processes and in malignancy

Az inzulinszerű növekedési faktor (IGF) szerepe a sejtosztódásban és a daganatképződésben kiterjedt kutatás tárgyát képezi. Korábban nyilvánvalóvá vált, hogy az IGF- és a hozzá kötődő jelátviteli rendszer proliferatív, differenciálódást elősegítő és antiapoptotikus hatást vált ki. Az IGF májban történő fiziológiás termelődésén túl jelentős mennyiségben kerül előállításra a daganatos sejtekben, s a keringésben fiziológiásan elérhető mennyiséget az IGF-kötő fehérjék (IGFBP) szabályozzák. A receptor-ligand kapcsolódást követően kialakuló tirozinkináz-aktivitás a foszfatidil-inozitol-3-kináz (PI3-K), valamint p38 mitogén aktiválta proteinkináz (MAPK) útvonalakon keresztül fejti ki hatását a sejtciklusra. Áttekintésre kerül a ligand, valamint a receptor bioszintézise, a jelátviteli rendszer működése és a daganatos sejtekben betöltött szerepe. A terápiás lehetőségek áttekintése során elemzésre kerülnek a preklinikai stádiumban levő szerek fontosabb ismérvei.

IGF-I activates caspases 3/7, 8 and 9 but does not induce cell death in colorectal cancer cells

BACKGROUND

Colorectal cancer is the third most common cancer in the western world. Chemotherapy is often ineffective to treat the advanced colorectal cancers due to the chemo-resistance. A major contributor to chemo-resistance is tumour-derived inhibition or avoidance of apoptosis. Insulin-like growth factor I (IGF-I) has been known to play a prominent role in colorectal cancer development and progression. The role of IGF-I in cancer cell apoptosis is not completely understood.

METHODS

Using three colorectal cancer cell lines and one muscle cell line, associations between IGF-I and activities of caspase 3/7, 8 and 9 have been examined; the role of insulin-like growth factor I receptor (IGF-IR) in the caspase activation has been investigated.

RESULTS

The results show that exogenous IGF-I significantly increases activity of caspases 3/7, 8 and 9 in all cell lines used; blocking IGF-I receptor reduce IGF-I-induced caspase activation. Further studies demonstrate that IGF-I induced caspase activation does not result in cell death. This is the first report to show that while IGF-I activates caspases 3/7, 8 and 9 it does not cause colorectal cancer cell death.

CONCLUSION

The study suggests that caspase activation is not synonymous with apoptosis and that activation of caspases may not necessarily induce cell death.

Apoptosis and colorectal cancer: implications for therapy

Colorectal cancer (CRC) is characterized by the partial suppression of apoptosis, which in turn gives tumours a selective advantage for survival and can cause current chemotherapy approaches to be ineffective. Recent progress in understanding the mechanisms of apoptosis in colorectal carcinogenesis has provided potential new targets for therapy. Here, we review recent studies of the regulation of apoptosis and its role in CRC initiation and progression, and we discuss the relationship between chemoresistance and the suppression of apoptosis. Recent progress in targeting apoptotic pathways and their regulators provide strategies for the exploration of novel therapies for CRC.