Chitosan, a multipurpose biomaterial, has been shown to exert effects against several types of cancer including oral cancer. However, the mechanisms underlying the anticancer activities of chitosan on oral squamous cell carcinoma (SCC) cells remain largely unknown. The present study aimed to compare the effects of low-molecular-weight chitosan (LMWC) and cisplatin on oral SCC Ca9-22 and non-cancer keratinocyte HaCaT cell lines. Cell viability and cell cycle profiles were measured by MTT assay and laser scanning cytometry, respectively. Apoptosis was examined by TUNEL assay and electron microscopy, followed by analysis of caspase activity. LMWC exhibited cytotoxic effects on Ca9-22, but not HaCaT cells, whereas cisplatin induced apoptosis in both types of cells. Exposure of Ca9-22 cells to LMWC led to G1/S cell cycle arrest and an increase of TUNEL-positive cells accompanied by an early apoptotic cell morphology and subtle increases of caspase activity. Short-term LMWC exposure was less cytotoxic to HaCaT cells than to Ca9-22 cells, and anticancer activity was exerted through induction of apoptosis and cell cycle arrest, suggesting that LMWC could be a promising natural anticancer agent with fewer side effects on normal cells. (J Oral Sci 56, 119-126, 2014)

Breast cancer stem cells (BCSCs) express high levels of the anti-apoptotic protein, survivin. This study aimed to discover a natural active compound with anti-cancer properties that targeted survivin in human breast cancer stem cells. From the seven examined compounds, andrographolide was selected as a lead compound through in silico molecular docking with survivin, caspase-9, and caspase-3. We found that the affinity between andrographolide and survivin is higher than that with caspase-9 and caspase-3. Human CD24-/CD44+ BCSCs were treated with andrographolide in vitro for 24 hours. The cytotoxic effect of andrographolide on BCSCs was compared to that on human mesenchymal stem cells (MSCs). The expression of survivin, caspase-9, and caspase-3 mRNA was analyzed using qRT-PCR, while Thr34-phosphorylated survivin and total survivin levels were determined using ELISA and Immunoblotting assay. Annexin-V/PI flow cytometry assays were performed to evaluate the apoptotic activity of andrographolide. Our results demonstrate that the CC₅₀ of andrographolide in BCSCs was 0.32mM, whereas there was no cytotoxic effect in MSCs. Moreover, andrographolide decreased survivin and Thr34-phosphorylated survivin, thus inhibiting survivin activation and increasing survivin mRNA in BCSCs. The apoptotic activity of andrographolide was revealed by the increase of caspase-3 mRNA and protein, as well as the increase in both the early and late phases of apoptosis. In conclusion, andrographolide can be considered an anti-cancer compound that targets BCSCs due to its molecular interactions with survivin, caspase-9, and caspase-3, which induce apoptosis. We suggest that the binding of andrographolide to survivin is a critical aspect of the effect of andrographolide.

The growth of tumour cells is closely related to cancer-associated fibroblasts (CAFs) present within their microenvironment. CAFs, the most abundant cells in tumour stroma, secrete growth factors that play pivotal roles in tumour cell proliferation, metabolism, angiogenesis and metastasis. Tumour cells adapt to rapid environmental changes from normoxia to hypoxia through metabolic interplay with CAFs. In this mini review, we discuss the role of lactate dehydrogenases (LDHs) and monocarboxylate transporters (MCTs) on the metabolic interplay between tumour cells and CAFs under hypoxia compared to normoxia. The LDHs catalyse the interchange of lactate and pyruvate, whereas MCTs facilitate the influx and efflux of monocarboxylates, especially lactate and pyruvate. To sum up, tumour cells switch their metabolic state between glycolysis and oxidative phosphorylation through metabolic interplay with CAFs, which exhibit the Warburg effect under hypoxia and reverse Warburg effect under normoxia.

Cell signaling is a vital part of biological life. It helps coordinating various cellular processes including cell survival, cell growth, cell death, and cell interaction with the microenvironment and other cells. In general, cell signaling involves the attachment of signaling molecules known as ligands to specific receptors on cell surface, which then activate downstream events that dictate the cell's response. One of the most studied ligands is transforming growth factor-beta (TGF-beta). TGF-beta signaling is mainly mediated by suppressor of mothers against decapentaplegic (Smad) proteins, but it also interacts with other pathways such as the Ras and mitogen-activated protein kinase (MAPK) signaling pathways. Furthermore, TGF-beta can have a dual role depending on the cellular and microenvironmental context, in which it can act as either a growth promoter or a growth inhibitor. It has been known that TGF-beta can self-induce its ligand production, thereby prolonging and amplifying its effect on cells and their microenvironment. The aim of this review is to discuss the regulation and signaling of TGF-beta autoinduction, which still remain to be elucidated. Several factors have been found to facilitate TGF-beta autoinduction, which include the activator protein-1 (AP1) complex, Smad3-dependent signaling, and non-Smad signaling pathways. On the other hand, the LIM (Lin11, Isl-1 and Mec-3) domain only 7 (LMO7) protein can suppress TGF-beta autoinduction by interfering with the activities of AP-1 and Smad3. Since TGF-beta autoinduction is implicated in various pathological conditions, better understanding of its regulation and signaling can provide new directions for therapy.

Tamoxifen is the first line drug used in the treatment of estrogen receptor-positive (ER+) breast cancer. The development of multidrug resistance (MDR) to tamoxifen remains a major challenge in the treatment of cancer. One of the mechanisms related to MDR is decrease of drug influx via overexpression of drug efflux transporters such as P-glycoprotein (P-gp/MDR1), multidrug resistance associated protein (MRP), or BCRP (breast cancer resistance protein). We aimed to investigate whether the sensitivity of tamoxifen to the cells is maintained through the short period and whether the expressions of several drug efflux transporters have been upregulated. We exposed MCF7 breast cancer cells with tamoxifen 1 μM for 10 passages (MCF7 (T)). The result showed that MCF7 began to lose their sensitivity to tamoxifen from the second passage. MCF7 (T) also showed a significant increase in all transporters examined compared with MCF7 parent cells. The result also showed a significant increase of CC50 in MCF7 (T) compared to that in MCF7 (97.54 μM and 3.04 μM, resp.). In conclusion, we suggest that the expression of several drug efflux transporters such as P-glycoprotein, MRP2, and BCRP might be used and further studied as a marker in the development of tamoxifen resistance.

TIt has previously been reported that transcription In vivo of the tRNA^Sec gene requires three promoter elements, a PSE and a TATA-box upstream of the coding region which are functionally interchangeable with the U6 snRNA gene counterparts and an Internal B-block, resembling that of classical tRNA genes (1). We have established an In vitro transcription system from HeLa cells in which three factors, which are either essential for or stimulate transcription were identified. Apart from the TATA-blnding protein TBP, the PSE-blnding protein PBP was found to be essentially required for expression of the gene. Depletion of PBP from cell extracts by PSE-oligonucleotides abolished tRNA^Sec transcription, which could be reconstituted by re-addition of partially purified PBP. Addition of Increasing amounts of recombinant human TBP to an S100 extract stimulated transcription of the tRNA^Sec, the mouse U6 snRNA and the human Y3 genes, an effect which was not observed In the case of a TATA-less tRNA gene. Purified human TFIIA strongly stimulated tRNA^Sec transcription in a fashion depending on the concentration of TBP. Surprisingly, partially purified TFIIIC was shown to be dispensable for transcription In vitro and unable to bind the B-block of this gene In vitro, although its sequence matches the consensus for this element. Collectively, these data suggest that the mechanism by which transcription complexes are formed on the tRNA^Sec gene is dramatically different from that observed for classical tRNA genes and much more resembles that observed for externally controlled pol III genes.