Current Cancer Drug Targets - Volume 13, Issue 1, 2013

Hyperforin is a prenylated phloroglucinol present in the medicinal plant St John's wort (Hypericum perforatum). The compound has many biological properties, including antidepressant, anti-inflammatory, antibacterial and antitumor activities. This review focuses on the in vitro antileukemic effects of purified hyperforin and related mechanisms in chronic lymphoid leukemia (CLL) and acute myeloid leukemia (AML) - conditions that are known for their resistance to chemotherapy. Hyperforin induces apoptosis in both CLL and AML cells. In AML cell lines and primary AML cells, hyperforin directly inhibits the kinase activity of the serine/threonine protein kinase B/AKT1, leading to activation of the pro-apoptotic Bcl-2 family protein Bad through its non-phosphorylation by AKT1. In primary CLL cells, hyperforin acts by stimulating the expression of the pro-apoptotic Bcl-2 family member Noxa (possibly through the inhibition of proteasome activity). Other hyperforin targets include matrix metalloproteinase-2 in AML cells and vascular endothelial growth factor and matrix metalloproteinase-9 in CLL cells - two mediators of cell migration and angiogenesis. In summary, hyperforin targets molecules involved in signaling pathways that control leukemic cell proliferation, survival, apoptosis, migration and angiogenesis. Hyperforin also downregulates the expression of P-glycoprotein, a protein that is involved in the resistance of leukemia cells to chemotherapeutic agents. Lastly, native hyperforin and its stable derivatives show interesting in vivo properties in animal models. In view of their low toxicity, hyperforin and its derivatives are promising antileukemic agents and deserve further investigation in vivo.

Pulmonary delivery of drug-loaded nanoparticles is a novel approach for lung cancer treatment and the conjugation of nanoparticles to a targeting ligand further promotes specificity of the carrier cargo to cancer cells. Notably, the epithelial cell adhesion molecule (EpCAM, CD326) is over expressed in lung cancer. Here, we report the safety and proof-of-concept efficacy of drug-loaded nanoparticles and EpCAM immunonanoparticles in a c-Raf transgenic lung cancer model. PEG-PLA nanoparticles and immunonanoparticles were prepared whereby paclitaxel palmitate (Pcpl) was incorporated as a medication for its common use in lung cancer treatment. Four doses of aerosolized nanoparticle formulations or vehicle were endotracheally administered to mice by consecutive or alternate regimes. Pulmonary delivery of drug loaded nano- and/or immunonanoparticle formulations elicited mild inflammation as evidenced by the slightly increased neutrophil and activated macrophage counts in bronchoalveolar lavage. No evidence for pulmonary toxicity following treatment with either blank or drug-loaded nano- and/or immunonanoparticles was observed. Proof-ofconcept efficacy was determined by serial CT scanning and histopathology. Animals treated with either EpCAM antibody or Pcpl solution or drug loaded nano- or immunonanoparticles inhibited disease progression. Conversely, disease progression was noted with vehicle treated animals with nearly 30% loss of their aerated lung volume. Importantly, treatment of mice with either Pcpl or EpCAM antibody solution caused 80% mortality and/or haemorrhage, respectively, thus causing unacceptable toxicity. In contrast, the survival of animals treated with either nano- or immunonanoparticles was 60 and 70%, respectively. Taken collectively, pulmonary delivered drug-loaded nano- and EpCAM immunonanoparticles were well tolerated and can be considered a promising strategy for improving lung cancer treatment.

Allogeneic stem cell transplantation is commonly used in the treatment of high-risk acute myeloid leukemia (AML). This intensive treatment has a high early transplant-related mortality, and an additional significant cause of death in these patients is later AML relapse. Retransplantation can be considered for a minority of patients, but only 10-20% of selected patients then achieve long-term survival. Donor lymphocyte infusion (DLI) has an antileukemic effect, but the effect of this treatment usually lasts for only 3-4 months. A possible strategy to improve the prognosis could be to combine antileukemic T-cell therapy (i.e. DLI) with AML-targeting therapy. Several aspects have to be considered for such approaches: (i) the therapy should have immunomodulatory rather than immunosuppressive effects; (ii) the regimen should have a low hematological toxicity to preserve residual normal bone marrow function; and (iii) the treatment should have a documented antileukemic effect. DLI elicit both graft versus host and graft versus leukemia effects, and could be added to pharmacological treatment. Epigenetic targeting should be considered in these patients because both demethylating agents as well as the histone deacetylase inhibitors have documented antileukemic effects and have a relatively low hematological toxicity. Other drugs to consider are thalidomide, lenalidomide, antiangiogenic agents, tyrosine kinase inhibitors and heat shock protein 90 inhibitors, which all have both antileukemic and immunomodulatory effects. Relatively few clinical studies are available for patients with this high-risk disease. The designs of future clinical trials have to carefully consider the antileukemic and immunomodulatory effects together with the risk of especially hematological toxicity.

Background: In patients with Osteosarcoma (OS), larger primary tumor size correlates with higher metastasis incidence and lower overall survival. Identifying the mechanisms that control primary tumor growth can lead to the new therapeutic approaches and improve prognosis. Cytoskeleton regulatory molecules play an important role in tumor cells proliferation and motility. In the current study, we investigated the role of scaffolding protein Cdc42-interacting protein 4 (CIP4) in OS. Methods: Murine OS cells, DLM8 were stably transfected with shCIP4 plasmid and their tumorigenic activity was studied in vitro and in vivo. The effect of CIP4 downregulation on cytoskeleton was studied by immunohistochemical analysis. Results: In vivo studies revealed that downregulation of CIP4 in OS tumor cells can inhibit primary subcutaneous tumor growth and delay spontaneous metastases growth in the animal lungs. In vitro studies confirmed that inhibiting CIP4 expression significantly reduced tumor cells invasiveness and migration. Changes in CIP4 expression altered its cellular localization pattern and tumor cell morphology, which could explain changes in OS cell behavior in vivo and in vitro. Cells with downregulated CIP4 showed lower levels of actin in cells along with fewer perinuclear actin stress filaments and actin bridges to the lipid bilayer of the cell membrane than control cells. Conclusions: This study presents compelling evidence that inhibition of CIP4 expression in OS cells impairs metastatic behavior of cells in vitro and prolongs survival of animals by inhibiting primary tumor growth. Although the lack of CIP4 in tumor cells did not prevent formation of metastasis, it did substantially delay their formation in the animals' lungs.

Effective treatments to prevent recurrence or progression of non-muscle-invasive bladder cancer, or to inhibit metastasis of muscle-invasive forms of the disease, would deliver significant patient benefit. Here the involvement of STAT signalling and the chemopreventive potential of diindolylmethane (DIM) in human bladder cancer were investigated. Muscle-invasive bladder cancer tissues were characterised by nuclear expression of phosphorylated STAT1, 3 and 5. In E-cadherin positive tumour cell lines (RT112, RT4, HT1376), STAT5 was constitutively phosphorylated, while E-cadherin negative lines (J82, T24, UMUC3) contained phosphoSTAT3. Knockdown of STAT3 induced G0/G1 arrest and inhibited adhesion in J82 cells. Knockdown of STAT1inhibited migration in J82 and RT112 lines. No significant increase in apoptosis was observed. In response to the Janus kinase inhibitor, AG490, RT112 and J82 cells initially underwent G0/G1 arrest, with RT112 cells subsequently exhibiting S phase arrest. Phosphorylation of STAT1Tyr701, STAT3Tyr705 and Ser727 and STAT5Tyr694 was inhibited by DIM, as was adhesion of J82 cells to collagen, an effect that was enhanced when STAT1 or 3 was reduced by siRNA. However, over-expression of STAT3C partially rescued the DIM inhibitory effect on collagen-mediated adhesion. Migration of both lines was inhibited by DIM, while transfection of constitutively active STAT3C enhanced migration of RT112 cells. DIM induced cell cycle arrest and apoptosis in three cell lines with different degrees of radioresistance. Taken together, these results suggest that inhibition of STAT signalling and/or treatment with DIM may decrease invasiveness of bladder cancer. DIM can induce apoptosis in cell lines which are radioresistant, so in combination with radiotherapy may be useful in overcoming such resistance.

Treatment outcomes for chronic myelogenous leukemia (CML) have shown major improvements as a result of the development of the tyrosine kinase inhibitors (TKIs) imatinib, nilotinib and dasatinib for the disease-specific molecular target BCR-ABL1 tyrosine kinase (TK), but a cure of CML by BCR-ABL1 TKIs has been rarely achieved. CML cells are protected from cytotoxic insults, including those by TKIs, through various collaborative BCR-ABL1- mediated and -independent mechanisms, as well as cell-intrinsic and -extrinsic molecular mechanisms. These protective mechanisms include overlapping cell signaling pathways for normal hematopoietic proliferation, modulation of molecules associated with the BCL2 family protein-regulated programmed cell death pathway, autophagic cell protection capability, bone marrow environment-mediated cell protective signaling, abnormally upregulated genetic instability and other BCRABL1- independent kinase activities. To develop a more effective treatment strategy for a cure by means of total leukemic cell killing, a thorough understanding of how CML cells survive and resist cytotoxic insults is essential. In this article, we review current knowledge about multifaceted BCR-ABL1-related and -unrelated mechanisms for survival and death of CML cells and present suggestions for the development of new therapeutic strategies for complete elimination of residual CML cells during TKI treatment.

Targets for cancer therapy are conventionally selected by identification of molecules acting downstream of established tumour suppressors and oncoproteins, such as p53, c-Myc and Ras. However, the forward genetics approach provides an alternative, conceptually distinct, strategy for identifying target molecules de novo. This approach, which uses unbiased selection protocols relying directly on the effects of the genes themselves on cell fate, has the potential to identify novel cancer targets which have not been highlighted by conventional approaches. PLAC8, a small cysteine-rich protein with little homology to other proteins, has been identified by both these strategies. Here we confirm that PLAC8 overexpression protects some cancer cell lines from apoptosis, but we also demonstrate for the first time that, in other cell lines, the effect of PLAC8 overexpression is reversed, and, in this context, PLAC8 induces apoptosis. In both cases siRNA-mediated down-regulation of PLAC8 confirms that the activity of endogenously expressed PLAC8 is consistent with that shown by exogenous PLAC8. The striking reversal of the effects of PLAC8 in different cell types is not readily explained by the level of PLAC8 expressed within the cells, by the differential expression of PLAC8 splice variants observed, or by the p53 status of the host cells. This intriguing contrast in the effects of PLAC8 on cell fate in different cellular contexts presents attractive possibilities for the development of novel therapies for cancers, such as pancreatic cancers, where PLAC8 has been shown to be overexpressed.

The use of adult stem cells as gene delivery vehicles is a novel and attractive strategy for cancer therapy. Mesenchymal stem cells (MSCs) provide a promising source for stem cell-based gene therapies. Interleukin-24 (IL24) has been suggested as an effective anticancer agent. However, a lack of tumor-targeted delivery and a host immune response to viral vehicles has hindered its application for cancer therapy. In this study, we evaluated the effects of IL24 delivered by MSCs as a therapeutic approach for lung cancer. We engineered human umbilical cord-derived MSCs (UC-MSCs) to efficiently deliver secretable IL24. We observed that IL24-transduced UC-MSCs (IL24-MSCs) inhibited the growth of A549 lung cancer cells by induction of apoptosis and cell cycle arrest. The IL24 proteins secreted by IL24-MSCs were involved in regulating the ERK-1/2, AKT and JNK signaling pathways. Additionally, MSCs-mediated IL24 expression led to an increase in the cleavage of caspases-3/8/9 and PARP, the Bax/Bcl-2 ratio, as well as the p21 expression in A549 cells. We also demonstrated that injection of IL24-MSCs significantly suppressed xenograft tumor growth. Moreover, the IL24-MSCs had anti-angiogenic effects both in vitro and in vivo. Taken together, our findings indicate that IL24 delivered by human UC-MSCs has the potential to be used as an alternative strategy for lung cancer therapy.

TRPC channels are Ca2+-permeable cationic channels controlling Ca2+ influx response to the activation of G protein-coupled receptors and protein tyrosine kinase pathways or the depletion of Ca2+ stores. Here we aimed to investigate whether TRPC can act as the potential therapeutic targets for ovarian cancer. The mRNAs of TRPC1, TRPC3, TRPC4 and TRPC6 were detected in human ovarian adenocarcinoma. The spliced variants of TRPC1β, TRPC3a, TRPC4β, TRPC4γ, and TRPC6 with exon 3 and 4 deletion were highly expressed in the ovarian cancer cells, and a novel spliced isoform of TRPC1 with exon 9 deletion (TRPC1E9del) was identified. TRPC proteins were also detected by Western blotting and immunostaining. The expression of TRPC1, TRPC3, TRPC4 and TRPC6 was significantly lower in the undifferentiated ovarian cancer cells, but all-trans retinoic acid up-regulated the gene expression of TRPCs. The expression level was correlated to the cancer differentiation grade. The non-selective TRPC channel blockers, 2-APB and SKF-96365, significantly inhibited the cell proliferation, whilst the increase of TRPC channel activity by trypsin promoted the cell proliferation. Transfection with siRNA targeting TRPC1, TRPC3, TRPC4 and TRPC6 or application of specific blocking antibodies targeting to TRPC channels inhibited the cell proliferation. On the contrary, overexpression of TRPC1, TRPC1E9del, TRPC3, TRPC4, and TRPC6 increased the cancer cell colony growth. These results suggest that TRPCs and their spliced variants are important for human ovarian cancer development and alteration of the expression or activity of these channels could be a new strategy for anticancer therapy.