Caspase-driven cancer therapies: Navigating the bridge between lab discoveries and clinical applications

Apoptosis is the cell's natural intrinsic regulatory mechanism of normal cells for programmed cell death, which plays an important role in cancer as a classical mechanism of tumor cell death causing minimal inflammation without causing damage to other cells in the vicinity. Induction of apoptosis by activation of caspases is one of the primary targets for cancer treatment. Over the years, a diverse range of natural, synthetic, and semisynthetic compounds and their derivatives have been investigated for their caspase-mediated apoptosis-induced anticancer activities. The review aims to compile the preclinical evidence and highlight the critical mechanistic pathways related to caspase-induced cell apoptosis in cancer treatment. The focus is placed on the key components of the mechanisms, including their chemical nature, and specific attention is given to phytochemicals derived from natural sources and synthetic and semisynthetic compounds. 180+ compounds from the past two decades with potential as anticancer agents are discussed in this review article. By summarizing the current knowledge and advancements in this field, this review provides a comprehensive overview of potential therapeutic strategies targeting apoptosis in cancer cells. The findings presented herein contribute to the ongoing efforts to combat cancer and stimulate further research into the development of effective and targeted anticancer therapies.

Is It Still Possible to Think about HSP70 as a Therapeutic Target in Onco-Hematological Diseases?

The search for molecules to be targeted that are involved in apoptosis resistance/increased survival and pathogenesis of onco-hematological malignancies is ongoing since these diseases are still not completely understood. Over the years, a good candidate has been identified in the Heat Shock Protein of 70kDa (HSP70), a molecule defined as “the most cytoprotective protein ever been described”. HSP70 is induced in response to a wide variety of physiological and environmental insults, allowing cells to survive lethal conditions. This molecular chaperone has been detected and studied in almost all the onco-hematological diseases and is also correlated to poor prognosis and resistance to therapy. In this review, we give an overview of the discoveries that have led us to consider HSP70 as a therapeutic target for mono- or combination-therapies in acute and chronic leukemias, multiple myeloma and different types of lymphomas. In this excursus, we will also consider HSP70 partners, such as its transcription factor HSF1 or its co-chaperones whose druggability could indirectly affect HSP70. Finally, we will try to answer the question asked in the title of this review considering that, despite the effort made by research in this field, HSP70 inhibitors never reached the clinic.

Cytotoxic and Antiproliferative Effects of β-Mangostin on Rat C6 Glioma Cells Depend on Oxidative Stress Induction via PI3K/AKT/mTOR Pathway Inhibition

Background

Glioma is the most common malignant tumor of the nervous system, which accounts for more than 45% of central nervous system tumors and seriously threatens our health. Because of high mortality rate, limitations, and many complications of traditional treatment methods, new treatment methods are urgently needed. β-Mangostin is a natural compound derived from the fruit of Garcinia mangostana L. and it has anticancer activity in several types of cancer cells. However, the antitumor effect of β-mangostin in glioma has not been clarified. Hence, this study aimed to investigate its therapeutic effects on gliomas.

Materials and Methods

To study the effect of β-mangostin on glioma cells, cell viability assay, reactive oxygen species production, cell cycle, apoptosis, and mitochondrial membrane potential were evaluated in the C6 cell line in vitro. Immunofluorescence and Western blotting were used to analyze protein expression and phosphorylation to study its mechanism of action. A subcutaneous xenograft model was used to investigate the effect of β-mangostin on tumorigenesis in vivo.

Results

We found that β-mangostin can inhibit glioma cell growth and induce oxidative damage in vitro. In addition, it reduces the phosphorylated form levels of PI3K, AKT and mTOR. Furthermore, the phosphorylated form levels of PI3K, AKT and mTOR were increased after the PI3K inhibitor was added. In vivo experiments showed that β-mangostin can inhibit tumor growth as shown by its reduced size and weight.

Conclusion

This study suggests that β-mangostin can inhibit cell proliferation and induce oxidative damage in cells. It is the first study to demonstrate that β-mangostin induces oxidative damage in glioma cells by inhibiting the PI3K/AKT/mTOR signaling pathway.

Cytotoxicity and nitric oxide inhibitory activities of Xanthones isolated from Calophyllum hosei Ridl

Previous studies on Calophyllum species have shown the existence of a wide variety of bioactive xanthones and coumarins. Phytochemical investigations carried out on the plant, Calophyllum hosei led to the isolation of eleven known xanthones, ananixanthone (1), 9-hydroxycalabaxanthone (2), dombakinaxanthone (3), thwaitesixanthone (4), caloxanthone B (5), trapezifolixanthone (6), β-mangostin (7), osajaxanthone (8), caloxanthone A (9), calozeyloxanthone (10) and rubraxanthone (11). The structures of these compounds were identified and elucidated using spectroscopic techniques such as NMR and MS. The cytotoxicity and nitric oxide production inhibitory activities of selected xanthones as well as the extracts were tested against HL-60 cells and RAW 264.7 murine macrophages, respectively. Among all tested compounds, β-mangostin exhibited appreciable cytotoxicity against HL-60 cells with the IC₅₀ value of 7.16 ± 0.70 µg/mL and rubraxanthone exhibited significant nitric oxide inhibitory activity against LPS induced RAW 264.7 murine macrophages with the IC₅₀ value of 6.45 ± 0.15 µg/mL.

β-Mangostin inhibits the metastatic power of cervical cancer cells attributing to suppression of JNK2/AP-1/Snail cascade

β-Mangostin is a natural mangostin with potent anticancer activity against various cancers. In this study, we further explored the anticancer activity of β-mangostin on cervical cancer cells. β-Mangostin did not affect cell viability and cell cycle distribution in HeLa and SiHa cells; however, it dose-dependently inhibited the migration and invasion of both the human cervical cancer cell lines. In addition, we observed that β-mangostin suppressed the expression of integrin αV and β3 and the downstream focal adhesion kinase/Src signaling. We also found that Snail was involved in the β-mangostin inhibited cell migration and invasion of HeLa cell. Then, our findings showed that β-mangostin reduced both nuclear translocation and messenger RNA expression of AP-1 and demonstrated that AP-1 could target to the Snail promoter and induce Snail expression. Kinase cascade analysis and reporter assay showed that JNK2 was involved in the inhibition of AP-1/Snail axis by β-mangostin in HeLa cells. These results indicate that β-mangostin can inhibit the mobility and invasiveness of cervical cancer cells, which may attribute to the suppression of both integrin/Src signaling and JNK2-mediated AP-1/Snail axis. This suggests that β-mangostin has potential antimetastatic potential against cervical cancer cells.

Protective functions of Lycium barbarum polysaccharides in H2O2-injured vascular endothelial cells through anti-oxidation and anti-apoptosis effects

Cell injury in the cardiovascular endothelia caused by oxidative stress is among the major inducers of endothelium dysfunction and serves an important role in initiating cardiovascular diseases (CVDs). Therefore, protecting and improving the normal function of endothelial cells are considered key measures against CVDs. As a traditional Chinese medicinal component, Lycium barbarum is regarded to have high medicinal value. The present study aimed to investigate the potential anti-apoptosis and anti-oxidation effects of Lycium barbarum polysaccharides (LBPs) on injured rat artery endothelial cells, to demonstrate the experimental and medicinal values of LBPs. In the present study, the aortic endothelial cells of rats were cultivated and randomly divided into five groups: A control group, H₂O₂-injured group (H₂O₂ group), H₂O₂+LBPs (110 µg/ml) group (low-dose group, LT), H₂O₂+LBPs (220 µg/ml) group (medium-dose group, MT) and H₂O₂+LBPs (440 µg/ml) group (high-dose group, HT). Among these, the activity of superoxide dismutase (SOD), and the levels of malondialdehyde (MDA) and nitric oxide (NO) were detected by colorimetry. Additionally, the expression of B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax) were detected by western blotting. It was observed that SOD activity and NO content decreased while MDA content increased significantly in the H₂O₂ group (P<0.05 vs. control); that SOD activity in the MT and HT group, and NO content in all three LBP groups were increased, while MDA content in the three LBP groups was decreased, compared with the H₂O₂ group (all P<0.05); that Bcl-2 expression decreased significantly in the H₂O₂ group while the expression of Bax increased significantly compared with the control group (both P<0.05); and that Bcl-2 expression in all three LBP groups increased, while Bax expression in the MT and HT groups decreased compared with the H₂O₂ group (all P<0.05), with these altered Bax levels being statistically similar to those in the control group (P>0.05). On light microscopy, the cells in the control group exhibited spindle-shaped morphology, consistent sizes, defined boundaries, and distinct nuclei of equivalent sizes with round or oval morphology. Additionally, the chromatin in the nuclei was evenly distributed, and all cells were adhered in a paving-stone arrangement. Notably, only few cells died. Conversely, the cells in the H₂O₂ group exhibited signs of damage and enlarged gaps, and focal cells died. In the HT group, the cells once again appeared adherent and exhibited similar morphological status to the normal cells. Overall, these results indicate that LBPs serve a protective role in oxidative-injured vascular endothelial cells through anti-apoptosis and anti-oxidation effects.

Orientin Induces G0/G1 Cell Cycle Arrest and Mitochondria Mediated Intrinsic Apoptosis in Human Colorectal Carcinoma HT29 Cells

Colorectal carcinoma is one of the utmost diagnosed cancer with a steep increase in mortality rate. The incidence has been increasing in developing countries like India due to a westernization life style. Flavonoids have been explored widely for its various pharmacological activity including antitumor activity. Orientin, an analogue of luteolin (citrus flavonoid) isolated from rooibos and tulsi leaves is also expected to deliver significant antitumor activity similar to that of luteolin. The present study anticipates exploring the antitumor activity of orientin against colorectal carcinoma cells (HT29). Orientin exhibited remarkable cytotoxicity and antiproliferative activity against HT29 cells, which is clearly evident from tetrazolium based cytotoxicity and lactate dehydrogenase release assays. Orientin induce G0/G1 cell cycle arrest and regulates cyclin and cyclin-dependent protein kinases in order to prevent the entry of the cell cycle to the S phase. Annexin V-FITC (V-Fluorescein Isothiocyanate) dual staining reveals the apoptotic induction ability of orientin. The Bcl-2 family proteins along with the inhibitor of apoptotic proteins were regulated and the tumor suppressor p-53 expression have been decreased. In conclusion, our results proposed that orientin could be a potent chemotherapeutic agent against colorectal cancer after ascertaining their molecular mechanisms.

Notopterol-induced apoptosis and differentiation in human acute myeloid leukemia HL-60 cells

Purpose: This study aims to observe the effects of notopterol on the apoptosis and differentiation of HL-60 cells and to explore the underlying molecular mechanisms.

Methods: Cell viability was assessed using sulforhodamine B assay. Cell proliferation was determined by the trypan blue dye exclusion test. Colony-forming units were assayed in methylcellulose. Apoptosis assays were carried out by annexin V-fluorescein isothiocyanate(FITC)/propidium iodide (PI) double staining, Hoechst 33342 staining, mitochondrial membrane potential, and Western blot. Wright–Giemsa staining, nitroblue tetrazolium (NBT) reduction assay, CD11b and CD14 and Western blot were detected for induction of differentiation. In addition, cell-cycle phase distribution was analyzed by flow cytometry and Western blot. The combination therapy of notopterol and all-trans retinoic acid (ATRA) on HL-60 cells was examined.

Results: Notopterol obviously inhibited the growth of HL-60 cells with an IC₅₀ value of 40.32 μM and remarkably reduced the number of colonies by 10, 20, and 40 µM. In addtion, notopterol induced the percentage of apoptotic HL-60 cells, reduced the mitochondrial membrane potential, decreased the protein expresstion of Bcl-2 and Mcl-1, and increased the expression of Bax, cleavage of caspase 9, caspase 3, and PARP. As for cell differentiation, notopterol clearly induced chromatin condensation; increased the nucleocytoplasmic ratio, nitroblue tetrazolium-positive cells, expression of CD14 and CD11b, and protein expression of c-Jun and Jun B, and decreased c-myc. Furthermore, notopterol induced the G0/G1 cell-cycle arrest as determined using flow cytometry, which may be related to the regulation of cell-cycle-related proteins p53, CDK2, CDK4, Cyclin D1, Cyclin E, and survivin. The combined use of notopterol and ATRA did not enhance the apoptotic effect as evidenced by cell viability test and Hoechst 33342. However, the combination of notopterol and ATRA enhanced the effect of inducing differentiation when compared with using either notopterol or ATRA alone, which can be evidenced by the increased nucleocytoplasmic ratio, NBT positive cells, and expression of CD14.

Conclusion: This is the first time it has been demonstrated that notopterol could induce apoptosis, differentiation, and G0/G1 arrest in human AML HL-60 cells, suggesting that notopterol has potential therapeutic effects on AML. The combination application of notopterol (20 and 40 μM) and ATRA (2 μM) could augment differentiation of HL-60 cells.

Natural Products and Acute Myeloid Leukemia: A Review Highlighting Mechanisms of Action

Recent findings have shown great potential of alternative interventions such as immunotherapy and natural products for acute myeloid leukemia (AML). This study aims to review the anti-AML effect of various natural compounds. Natural compounds were classified into five groups: alkaloids, carotenoids, nitrogen-containing compounds, organosulfur compounds or phenolics based on each compound’s chemical properties. Fifty-eight studies were collected and reviewed in this article. Phenolics are the most abundant group to have an apoptotic effect over AML cells, while other groups have also shown significant apoptotic effects. Some compounds induced apoptosis by regulating unique mechanism like human telomerase reverse transcriptase (hTERT) or laminin receptor (67LR), while others modified caspases, poly (adp-ribose) polymerase (PARP) and p53. Further study is required to identify side-effects of potent compounds and the synergistic effects of combination of two or more natural compounds or existing conventional anti-AML drugs to treat this dreadful disease.

Inhibition of JAK2/STAT3 Signaling Pathway Suppresses Proliferation of Burkitt's Lymphoma Raji Cells via Cell Cycle Progression, Apoptosis, and Oxidative Stress by Modulating HSP70

Background

The aim of this study was to investigate the effect of the JAK2/STAT3 pathway on the proliferation, cell cycle distribution, apoptosis, and oxidative stress of Raji cells via regulating HSP70 expression.

Material/Methods

Raji cells were divided into Blank, HSP70 siRNA, NC siRNA, AG490 (a JAK2/STAT3 signaling pathway inhibitor), and HSP70 siRNA + rh JAK2 (recombinant human JAK2) groups. HSP70 expression was detected by quantitative real-time reverse transcription-PCR (qRT-PCR); the expression levels of HSP70 and JAK2/STAT3 pathway-related proteins were evaluated by Western blotting; cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays; cell cycle distribution was observed by flow cytometry; cell apoptosis was tested by Annexin V-FITC/PI and Hoechst 33342/PI staining; reactive oxygen species (ROS) production was measured by dichloro-dihydro-fluorescein diacetate (DCFH-DA) assays; and MDA content and SOD and GSH-Px activities were determined using detection kits.

Results

AG490 obviously down-regulated HSP70 expression, inhibited proliferation, induced cell cycle arrest at the G0/G1 phase, and promoted apoptosis in Raji cells; these effects were similar to the effects of HSP70 siRNA. Furthermore, ROS production and MDA content were increased in Raji cells treated with HSP70 siRNA or AG490, while SOD and GSH-Px activities were reduced. Raji cells in the HSP70 siRNA + rh JAK2 group did not significantly differ from those in the Blank group in regards to proliferation, cell cycle, apoptosis, and oxidative stress.

Conclusions

Blocking the JAK2/STAT3 signaling pathway may inhibit proliferation, induce cell cycle arrest, and promote oxidative stress and apoptosis in Raji cells via the down-regulation of HSP70.