Tumorigenicity of MCF-7 human breast cancer cells lacking the p38α mitogen-activated protein kinase

Insulin-like growth factor and epidermal growth factor signaling in breast cancer cell growth: focus on endocrine resistant disease

Breast cancer is the most common type of cancer for women worldwide with a lifetime risk amounting to a staggering total of 10%. It is well established that the endogenous synthesis of insulin-like growth factor (IGF) and epidermal growth factor (EGF) polypeptide growth factors are closely correlated to malignant transformation and all the steps of the breast cancer metastatic cascade. Numerous studies have demonstrated that both estrogens and growth factors stimulate the proliferation of steroid-dependent tumor cells, and that the interaction between these signaling pathways occurs at several levels. Importantly, the majority of breast cancer cases are estrogen receptor- (ER-) positive which have a more favorable prognosis and pattern of recurrence with endocrine therapy being the backbone of treatment. Unfortunately, the majority of patients progress to endocrine therapy resistant disease (acquired resistance) whereas a proportion of patients may fail to respond to initial therapy (de novo resistance). The IGF-I and EGF downstream signaling pathways are closely involved in the process of progression to therapy resistant disease. Modifications in the bioavailability of these growth factors contribute critically to disease progression. In the present review therefore, we will discuss in depth how IGF and EGF signaling participate in breast cancer pathogenesis and progression to endocrine resistant disease.

Estrogen receptor β isoform 5 confers sensitivity of breast cancer cell lines to chemotherapeutic agent-induced apoptosis through interaction with Bcl2L12

Alternative splicing of estrogen receptor β (ERβ) yields five isoforms, but their functions remain elusive. ERβ isoform 5 (ERβ5) has been positively correlated with better prognosis and longer survival of patients with breast cancer (BCa) in various clinical studies. In this study, we investigated the inhibitory role of ERβ5 in BCa cells. Although ERβ5 does not reduce proliferation of BCa cell lines MCF-7 and MDA-MB-231, its ectopic expression significantly decreases their survival by sensitizing them to doxorubicin- or cisplatin-induced apoptosis through the intrinsic apoptotic pathway. Moreover, we discovered Bcl2L12, which belongs to the Bcl-2 family regulating apoptosis, to be a specific interacting partner of ERβ5, but not ERβ1 or ERα, in an estradiol-independent manner. Knockdown of Bcl2L12 enhanced doxorubicin- or cisplatin-induced apoptosis, and this process was further promoted by ectopic expression of ERβ5. Whereas Bcl2L12 was previously shown to inhibit apoptosis through binding to caspase 7, such interaction is reduced in the presence of ERβ5, suggesting a mechanism by which ERβ5 sensitizes cells to apoptosis. In conclusion, ERβ5 interacts with Bcl2L12 and functions in a novel estrogen-independent molecular pathway that promotes chemotherapeutic Agent-Induced in vitro apoptosis of BCa cell lines.

Thymoquinone induces apoptosis in oral cancer cells through p38β inhibition

Oral cancer is a common malignancy associated with high morbidity and mortality. While p38 MAPK is reported to be involved in different cellular activities such as proliferation and differentiation, reports rarely define the roles of the individual members of the p38 MAPK family in cancer. We used two unique cell lines developed by our lab representing chemically induced oral cancer cells (T28) and non-tumor cells (N28) obtained from tissues surrounding the induced cancer as a model to screen out whether p38 MAPK is involved in the malignant transformation processes. The results suggest an association between p38β not p38α and oral cancer development. Additionally, the anti-cancer activity of thymoquinone (TQ) was screened out and we found evidences suggesting that the anti-tumor activity of TQ may be attributed to the downregulation of p38β MAPK.

Serum protein N-glycan alterations of diethylnitrosamine-induced hepatocellular carcinoma mice and their evolution after inhibition of the placental growth factor

Placental growth factor (PlGF) inhibition produced promising results in reducing tumor burden in a diethylnitrosamine (DEN)-induced mouse model for hepatocellular carcinoma (HCC). The aim of this study was to non-invasively assess the improved histology by performing a serum glycomic analysis. To elucidate the molecular mechanism underlying the observed glycomic effects, we investigated the transcription and expression of E26 transformation-specific sequence 1 (Ets-1), a transcription factor essential for the glycomic and angiogenic changes in malignant transformation, including its different phosphorylated forms that result from activation of the MAP kinase and a Ca(2+)-dependent pathway. In addition, three Ets-1-dependent glycosyltransferase genes, Mgat4a, Mgat4b, and Mgat5, were also evaluated. HCC was induced in mice by weekly injections with DEN for 16, 20, 25, and 30 w. In the treatment study, mice were injected with DEN for 25 w and subsequently treated with PlGF antibodies (5D11D4) for 5 w. Finally, PlGF-/- mice were injected with DEN for 20, 25, and 30 w. Serum N-glycans were analyzed with DNA sequencer-assisted fluorophore-assisted capillary electrophoresis and compared with histology. Maximum altered N-glycan phenotype was reached after 20 w of DEN-injections, i.e., when the first neoplastic lesions started to appear. 5D11D4-treatment improved the glycomic phenotype in that 7 of the 11 altered glycans tended to normalize. The PlGF-/- mice also showed a normalization trend, although not to the same extent of the treatment group. Number of Ets1, Mgat4a, Mgat4b, and Mgat5 transcripts increased considerably in DEN-injected mice, however, a non-significant decrease was observed after 5D11D4-treatment. On the protein level, 5D11D4-treatment had a prominent effect on the MAP kinase pathway with a significant p38 activation, yet independent of Ets-1 function.

Human breast carcinoma cells are induced to apoptosis by samsum ant venom through an IGF-1-dependant pathway, PI3K/AKT and ERK signaling

In the present study we evaluated the anti-tumor potential of samsum ant venom (SAV) from Pachycondyla sennaarensis on the human breast carcinoma cell line MCF-7. We found that SAV induced growth arrest of MCF-7 cells without affecting the viability of MCF-10 (non-tumorigenic normal breast epithelial cells) and normal PBMCs. We then analyzed its impact on IGF-1-mediated MCF-7 cell proliferation and its effect on the underlying IGF-1 signaling pathways. Using flow cytometry analysis, we showed that the percentage of apoptotic cells was fourfold higher in SAV-treated cells as compared to untreated cells. More importantly, treatment with SAV induced a marked reduction in actin polymerization and a subsequent marked reduction in IGF-1-mediated cell proliferation. In addition to growth-inhibitory and pro-apoptotic effects, significant reductions were also observed in the phosphorylation of AKT and ERK, but not p38MAPK, in SAV-treated cells as compared to untreated cells. Our data reveal unique anti-tumor effects of samsum ant venom.

T-LAK cell-originated protein kinase (TOPK) phosphorylation of MKP1 protein prevents solar ultraviolet light-induced inflammation through inhibition of the p38 protein signaling pathway

Solar UV radiation is a major environmental factor that causes DNA damage, inflammation, and even skin cancer. T-LAK cell-originated protein kinase (TOPK) is expressed widely in both normal and cancer cells and functions to inhibit apoptosis and promote carcinogenesis. However, its function in inflammation is not known. The p38 MAPK signaling pathway plays an important role in solar UV light-induced inflammation. In this study, we found that TOPK negatively regulated the activity of p38α by phosphorylating the p38α-specific phosphatase MKP1 and enhancing the stability of MKP1. Notably, the absence of TOPK in mice resulted in a striking increase in skin inflammation. Therefore, we conclude that TOPK has a protective function in solar UV light-induced inflammation.