Bioinformatics-based discovery and characterization of an AKT-selective inhibitor 9-chloro-2-methylellipticinium acetate (CMEP) in breast cancer cells

Knockdown of hnRNP A2/B1 inhibits cell proliferation, invasion and cell cycle triggering apoptosis in cervical cancer via PI3K/AKT signaling pathway

Cervical cancer is currently one of the major threats to women's health. The overexpression of heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) as the biomarker has been investigated in various cancers. In our previous study, we found that lobaplatin induced apoptosis and cell cycle arrest via downregulation of proteins including hnRNP A2/B1 in cervical cancer cells. However, the underlying relationship between hnRNP A2/B1 and cervical cancer remained largely unknown. hnRNP A2/B1 knock-down in HeLa and CaSki cells was performed by shRNA transfection. The expression of hnRNP A2/B1 was detected by western blot and Quantitative Real-time PCR. Cell proliferation, migration, invasion and the IC₅₀ of lobaplatin and irinotecan were determined by MTT assay, Transwell assay, Plate colony formation assay and wound healing assay. Flow cytometry was perfomed to investigate cell apoptosis and the cell cycle. The expression of PI3K, AKT, p-AKT, p21, p27, caspase-3, cleaved caspase-3 were revealed by western blot. Nude mouse xenograft model was undertaken with HeLa cells and the xenograft tumor tissue samples were analyzed for the expression of PCNA and Ki-67 by immunohistochemistry and the cell morphology was evaluated by hematoxylin and eosin (H&E). Results revealed that hnRNP A2/B1 was successfully silenced in HeLa and CaSki cells. hnRNP A2/B1 knock-down significantly induced the suppression of proliferation, migration, invasion and also enhancement of apoptosis and reduced the IC₅₀ of lobaplatin and irinotecan. The expression of p21, p27 and cleaved caspase-3 in shRNA group were significantly upregulated and the expression of p-AKT was reduced both in vitro and in vivo. The results of immunohistochemistry showed that PCNA and Ki-67 were significantly downregulated in vivo. The growth of nude mouse xenograft tumor was significantly reduced by hnRNP A2/B1 knock-down. Taken together, these data indicate that inhibition of hnRNP A2/B1 in cervical cancer cells can inhibit cell proliferation and invasion, induce cell-cycle arrestment and trigger apoptosis via PI3K/AKT signaling pathway. In addition, after silencing hnRNP A2/B1 can increase the sensitivity of cervical cancer cells to lobaplatin and irinotecan.

Facilitating Akt clearance via manipulation of Hsp70 activity and levels

Members of the 70-kDa heat shock family can control and manipulate a host of oncogenic client proteins. This role of Hsp70 in both the folding and degradation of these client proteins makes it a potential drug target for certain forms of cancer. The phenothiazine family of compounds, as well as the flavonoid myricetin, was recently shown to inhibit Hsp70-ATPase activity, whereas members of the dihydropyrimidine family stimulated ATPase function. Akt, a major survival kinase, was found to be under the regulation of Hsp70, and when the ATPase activity of Hsp70 was increased or decreased by these compounds, Akt levels were also increased or decreased. Also, increasing Hsp70 levels concurrent with inhibition of its ATPase function synergistically reduced Akt levels to a greater extent than either manipulation alone, providing new insights about client fate decisions. Akt reductions mediated by Hsp70 inhibitors were prevented when Hsp70 expression was silenced with small interfering RNA. Inhibiting Hsp70 ATPase function produced cytotoxic events only in breast cancer cell lines where Akt dysfunction was previously shown, suggesting therapeutic specificity depending on the Hsp70 client profile. Thus, increasing Hsp70 levels combined with inhibiting its ATPase function may serve to dramatically reduce Akt levels and facilitate cell death in certain types of cancer.

Treatment combinations targeting apoptosis to improve immunotherapy of melanoma

Immunotherapy based on T cell responses to the tumor is believed to involve killing of cancer cells by induction of apoptosis. The predominant mechanisms are death ligand-induced signaling mainly by TNF-related apoptosis-inducing ligand (TRAIL) mediated by CD4 T cells, monocytes and dendritic cells, and perforin/granzyme mediated apoptosis mediated by CD8 T cells and NK cells. Resistance against TRAIL involves loss of TRAIL death receptors and/or activation of the MEK and/or Akt signal pathways. Resistance to CD8 CTL responses also involves activation of the MEK and/or Akt pathways. Apoptosis induced by immune responses is regulated by the Bcl-2 family of proteins. Many reagents have been developed against the Bcl-2 antiapoptotic proteins and clinical trials combining them with immunotherapy are awaited. The second group of agents that regulate the Bcl-2 family of proteins are the signal pathway inhibitors. Clinical trials with inhibitors of RAS, RAF or MEK are in progress and would appear an exciting combination with immunotherapy. One of the main drivers of resistance to apoptosis are adaptive mechanisms that allow cancer cells to overcome endoplasmic reticulum (ER) stress. These adaptive mechanisms inhibit practically all known apoptotic pathways and create an acidic environment that may reduce infiltration of lymphocytes against the tumor. The signal pathway inhibitors may be effective against these adaptive processes but additional agents that target ER stress pathways are in development. In conclusion, combination of immunotherapy with agents that target antiapoptotic mechanisms in cancer cells offers a new approach that requires evaluation in clinical trials.

Small molecules and targeted therapies in distant metastatic disease

Chemotherapy, biological agents or combinations of both have had little impact on survival of patients with metastatic melanoma. Advances in understanding the genetic changes associated with the development of melanoma resulted in availability of promising new agents that inhibit specific proteins up-regulated in signal cell pathways or inhibit anti-apoptotic proteins. Sorafenib, a multikinase inhibitor of the RAF/RAS/MEK pathway, elesclomol (STA-4783) and oblimersen (G3139), an antisense oligonucleotide targeting anti-apoptotic BCl-2, are in phase III clinical studies in combination with chemotherapy. Agents targeting mutant B-Raf (RAF265 and PLX4032), MEK (PD0325901, AZD6244), heat-shock protein 90 (tanespimycin), mTOR (everolimus, deforolimus, temsirolimus) and VEGFR (axitinib) showed some promise in earlier stages of clinical development. Receptor tyrosine-kinase inhibitors (imatinib, dasatinib, sunitinib) may have a role in treatment of patients with melanoma harbouring c-Kit mutations. Although often studied as single agents with disappointing results, new targeted drugs should be more thoroughly evaluated in combination therapies. The future of rational use of new targeted agents also depends on successful application of analytical techniques enabling molecular profiling of patients and leading to selection of likely therapy responders.

Sphingolipids as determinants of apoptosis and chemoresistance in the MCF-7 cell model system

An estimated 182,640 women and 1,990 men were diagnosed with breast cancer in 2008, and approximately 40,480 women and 450 men died from the disease. Thus, continued mechanistic studies are needed to understand the causes and develop additional therapeutics for this complicated disease. The MCF-7 cell system is one of the most recognized models for estrogen receptor (ER)-positive breast cancer and has generated approximately 13,000 publications cited in PubMed to date. A number of clues for biological mechanisms related to apoptotic/anti-apoptotic pathways and chemoresistance were elucidated and summarized in our previous review. The focus of this review is new knowledge of the central role of sphingolipid signaling in apoptotic mechanisms in estrogen receptor-positive breast cancer. The ultimate goal is to target crucial steps in survival signaling pathways that may ultimately provide additional translational solutions to the successful pharmacologic treatment of breast cancer.