Insulin-like Growth Factor-I Receptor Signaling Pathway Induces Resistance to the Apoptotic Activities of SCH66336 (Lonafarnib) through Akt/Mammalian Target of Rapamycin–Mediated Increases in Survivin Expression

The identities of insulin signaling pathway are affected by overexpression of Tau and its phosphorylation form

Introduction

Hyperphosphorylated Tau formed neurofibrillary tangles was one of the major neuropathological hallmarks of Alzheimer's disease (AD). Dysfunctional insulin signaling in brain is involved in AD. However, the effect of Tau pathology on brain insulin resistance remains unclear. This study explored the effects of overexpressing wild-type Tau (WTau) or Tau with pseudo-phosphorylation at AT8 residues (PTau) on the insulin signaling pathway (ISP).

Methods

293T cells or SY5Y cells overexpressing WTau or PTau were treated with or without insulin. The elements in ISP or the regulators of IPS were analyzed by immunoblotting, immunofluorescent staining and co-immunoprecipitation. Akt inhibitor MK2206 was used for evaluating the insulin signaling to downstream of mTOR in Tau overexpressing cells. The effects of anti-aging drug lonafarnib on ISP in WTau or PTau cells were also analyzed with immunoblotting. Considering lonafarnib is an inhibitor of FTase, the states of Rhes, one of FTase substrate in WTau or PTau cells were analyzed by drug affinity responsive target stability (DARTS) assay and the cellular thermal shift assay (CETSA).

Results

WTau or PTau overexpression in cells upregulated basal activity of elements in ISP in general. However, overexpression of WTau or PTau suppressed the ISP signaling transmission responses induced by insulin simulation, appearing relative higher response of IRS-1 phosphorylation at tyrosine 612 (IRS-1 p612) in upstream IPS, but a lower phosphorylation response of downstream IPS including mTOR, and its targets 4EPB1 and S6. This dysregulation of insulin evoked signaling transmission was more obvious in PTau cells. Suppressing Akt with MK2206 could compromise the levels of p-S6 and p-mTOR in WTau or PTau cells. Moreover, the changes of phosphatases detected in WTau and PTau cells may be related to ISP dysfunction. In addition, the effects of lonafarnib on the ISP in SY5Y cells with WTau and PTau overexpression were tested, which showed that lonafarnib treatment resulted in reducing the active levels of ISP elements in PTau cells but not in WTau cells. The differential effects are probably due to Tau phosphorylation modulating lonafarnib-induced alterations in Rhes, as revealed by DARTS assay.

Conclusion and discussion

Overexpression of Tau or Tau with pseudo-phosphorylation at AT8 residues could cause an upregulation of the basal/tonic ISP, but a suppression of insulin induced the phasic activation of ISP. This dysfunction of ISP was more obvious in cells overexpressing pseudo-phosphorylated Tau. These results implied that the dysfunction of ISP caused by Tau overexpression might impair the physiological fluctuation of neuronal functions in AD. The different effects of lonafarnib on ISP between WTau and PTau cells, indicating that Tau phosphorylation mediates an additional effect on ISP. This study provided a potential linkage of abnormal expression and phosphorylation of Tau to the ISP dysfunction in AD.

The combined therapy of mesenchymal stem cell transplantation and resveratrol for diabetes: Future applications and challenges

Diabetes mellitus (DM) is a worldwide chronic epidemic disease of impaired glucose metabolism. Transplantation of mesenchymal stem cells (MSCs) is considered a promising emerging treatment strategy for diabetes. However, the harsh internal environment of DM patients can inhibit the treatment effects of transplanted MSCs. Fortunately, this adverse effect can be reversed by resveratrol (Res). Therefore, we investigated and summarized relevant studies on the combined treatment of diabetes with MSCs and resveratrol. This review presents the therapeutic effects of this combination therapy strategy on DM in glycemic control, anti-inflammatory, anti-oxidative stress and anti-fibrotic. Moreover, this review explained the mechanisms of MSCs and resveratrol in diabetes treatment from 3 aspects, including promoting cell survival and inhibiting apoptosis, inhibiting histiocyte fibrosis, and improving glucose metabolism. These findings help to understand in-depth mechanisms of the treatment of DM and help to propose a potential treatment strategy for DM and its complications.

Immunohistochemical expression of insulin-like growth factor-1Ec in primary endometrial carcinoma: Association with PTEN, p53 and survivin expression

Chronic hyperinsulinemia due to insulin resistance and elevated levels of insulin-like growth factor (IGF)-1 and IGF-2 are suggestive of a significantly higher risk of endometrial carcinoma. There is a wealth of evidence showing differential expression of IGF-1 isoforms in various types of cancer. In the present study, 99 archived endometrial carcinoma tissue sections were retrospectively assessed by immunohistochemistry for IGF-1Ec isoform expression. Expression of IGF-1Ec was also assessed in nine cases of non-neoplastic endometrial tissue adjacent to the tumor, in 30 cases with normal endometrium and in 30 cases with endometrial hyperplasia. Furthermore, the association between IGF-1Ec and the concurrent expression of phosphatase and tensin homologue deleted on chromosome 10 (PTEN), p53 or survivin was assessed, as well as their combined expression in association with clinicopathological variables. In endometrial carcinoma, IGF-1Ec expression was high in non-endometrioid carcinoma (serous papillary or clear cell carcinoma) compared with that in endometrioid adenocarcinoma. IGF-1Ec expression was also high in the presence of tumoral necrosis. Furthermore, there was a significant correlation between the histological differentiation and the sum of staining intensity and the number of IGF-1Ec immunopositive cells in endometrial carcinoma. There was a moderate negative correlation between co-expression of IGF-1Ec and PTEN, for both the number of immunopositive cells (P=0.006, ρ=−0.343) and the sum of staining (scores and intensity; P=0.006, ρ=−0.343). Furthermore, there was a positive correlation between the sum of staining (scores and intensity) and co-expression of IGF-1Ec and survivin (P=0.043, ρ=0.225). However, there was no association between concomitant expression of IGF-1Ec and p53. These results emphasized the importance of IGF-1Ec expression during development of non-estrogen dependent endometrial adenocarcinoma. IGF-1Ec and PTEN may function opposingly during endometrial carcinogenesis. By contrast, IGF-1Ec and survivin may share common molecular pathways and may promote, in parallel, tumoral development.

Autophagy as a Potential Therapy for Malignant Glioma

Glioma is the most frequent and aggressive type of brain neoplasm, being anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM), its most malignant forms. The survival rate in patients with these neoplasms is 15 months after diagnosis, despite a diversity of treatments, including surgery, radiation, chemotherapy, and immunotherapy. The resistance of GBM to various therapies is due to a highly mutated genome; these genetic changes induce a de-regulation of several signaling pathways and result in higher cell proliferation rates, angiogenesis, invasion, and a marked resistance to apoptosis; this latter trait is a hallmark of highly invasive tumor cells, such as glioma cells. Due to a defective apoptosis in gliomas, induced autophagic death can be an alternative to remove tumor cells. Paradoxically, however, autophagy in cancer can promote either a cell death or survival. Modulating the autophagic pathway as a death mechanism for cancer cells has prompted the use of both inhibitors and autophagy inducers. The autophagic process, either as a cancer suppressing or inducing mechanism in high-grade gliomas is discussed in this review, along with therapeutic approaches to inhibit or induce autophagy in pre-clinical and clinical studies, aiming to increase the efficiency of conventional treatments to remove glioma neoplastic cells.

YM155 sensitizes non-small cell lung cancer cells to EGFR-tyrosine kinase inhibitors through the mechanism of autophagy induction

Resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), such as erlotinib and gefitinib, is a major clinical problem in the treatment of patients with non-small cell lung cancer (NSCLC). YM155 is a survivin small molecule inhibitor and has been demonstrated to induce cancer cell apoptosis and autophagy. EGFR-TKIs have been known to induce cancer cell autophagy. In this study, we showed that YM155 markedly enhanced the sensitivity of erlotinib to EGFR-TKI resistant NSCLC cell lines H1650 (EGFR exon 19 deletion and PTEN loss) and A549 (EGFR wild type and KRAS mutation) through inducing autophagy-dependent apoptosis and autophagic cell death. The effects of YM155 combined with erlotinib on apoptosis and autophagy inductions were more obvious than those of YM155 in combination with survivin knockdown by siRNA transfection, suggesting that YM155 induced autophagy and apoptosis in the NSCLC cells partially depend on survivin downregulation. Meanwhile, we found that the AKT/mTOR pathway is involved in modulation of survivin downregulation and autophagy induction caused by YM155. In addition, YM155 can induce DNA damage in H1650 and A549 cell lines. Moreover, combining erlotinib further augmented DNA damage by YM155, which were retarded by autophagy inhibitor 3MA, or knockdown of autophagy-related protein Beclin 1, revealing that YM155 induced DNA damage is autophagy-dependent. Similar results were also observed in vivo xenograft experiments. Therefore, combination of YM155 and erlotinib offers a promising therapeutic strategy in NSCLC with EGFR-TKI resistant phenotype.

The combination of everolimus and terameprocol exerts synergistic antiproliferative effects in endometrial cancer: molecular role of insulin-like growth factor binding protein 2

Oncogenic PIK3CA mutations are common in endometrial cancers, and the PI3K/AKT/mTOR pathway is targetable by drugs. We sought to investigate whether the combination of an mTOR inhibitor, everolimus (RAD001), and an AKT inhibitor, terameprocol (M4N), exerts better antiproliferative effects in endometrial cancer. The molecular mechanisms underlying their pharmacological action were also examined. The combination of RAD001 and M4N exerted in vitro synergistic effects on cell viability, apoptosis, and expression of IGFBP2 in endometrial cancer cells. Mechanistically, the Sp1 site on the IGFBP2 promoter was required for RAD001- and M4N-induced downregulation. IGFBP2 protein expression was higher in endometrial cancer than in the normal endometrium (P < 0.001). Furthermore, elevated IGFBP2 histoscores were significantly associated with a lower overall survival (P = 0.021). In conclusion, our in vitro results demonstrate that RAD001 and M4N exert synergistic antiproliferative effects against endometrial cancer cells, which appeared to be mediated by the inhibition of IGFBP2, a key anti-apoptotic regulator. Further clinical studies of this drug combination in patients with endometrial cancer may be warranted, especially in the presence of PIK3CA and IGFBP2 aberrations. KEY MESSAGES: RAD001 and M4N synergistically suppress endometrial cancer growth. IGFBP2 is overexpressed in endometrial cancer. The combination of RAD001 and M4N significantly reduces IGFBP2 overexpression. Sp1 binding site on the IGFBP2 promoter is required for RAD001- and M4N-induced downregulation. High IGFBP2 histoscore in endometrial cancer portends a poor prognosis.

Prodigiosin produced by Serratia marcescens inhibits expression of MMP-9 and survivin and promotes caspase-3 activation with induction of apoptosis in acute lymphoblastic leukaemia cells

AIMS

Matrix metalloproteinase-9 (MMP-9) and survivin are involved in several steps of carcinogenesis in acute lymphoblastic leukaemia (ALL). Yet, no MMP-9 and survivin-modulating drugs with low toxicity on normal cells but high efficacy against high MMP-9- and survivin-expressing leukaemia cells have been approved for clinical application in ALL. Prodigiosin, a secondary metabolite of Serratia marcescens, induces apoptosis in different kinds of cancer cells with low toxicity on normal cells. However, little is known about the effects of this compound on the high MMP-9- and survivin-expressing leukaemia cells.

METHODS AND RESULTS

CCRF-CEM cells as a model for high MMP-9- and survivin-expressing ALL cells were treated with 100, 200 and 400 nmol l^-1 prodigiosin after which cell number, proliferation rate, MMP-9 and survivin expression, caspase-3 activation and apoptosis were evaluated. After 24-, 48-, and 72-h treatments with 100, 200 and 400 nmol l^-1 prodigiosin, proliferation rates were measured to be 92·3-76·7%, 82-63% and 63·7-46·6% respectively. Treatment with prodigiosin for 48 h decreased MMP-9 mRNA levels followed by decreases in secreted (S) and intracellular (I) MMP-9 protein levels by 20-22% and 69-72% for 100-400 nmol l^-1 prodigiosin respectively. Prodigiosin decreased survivin protein levels from 40 to 26% followed by 3·7-5·6-fold increases in caspase-3 activation for the aforementioned prodigiosin concentration ranges. Treatment with 100-400 nmol l^-1 prodigiosin increased the caspase-3/survivin, caspase-3/I-MMP-9 and caspase-3/S-MMP-9 ratios by 6-7·3-, 11·5-19·1- and 4·9-6·8-fold increases respectively. A dramatic increase in the number of apoptotic cells was also observed with increasing prodigiosin concentrations.

CONCLUSION

The inhibitory effects of prodigiosin on MMP-9 and survivin expression, as well as its pro-apoptotic capacity, represent a novel therapeutic avenue against ALL cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings provide an important and interesting basis to develop a new therapeutic compound with high potential against ALL cells.

FTI-277 inhibits smooth muscle cell calcification by up-regulating PI3K/Akt signaling and inhibiting apoptosis

Background

Vascular calcification is associated with increased cardiovascular morbidity and mortality in patients with atherosclerosis, diabetes and chronic kidney disease. However, no viable treatments for this condition have been identified. This study aimed to determine whether farnesyl transferase inhibitors (FTIs) can reduce vascular calcification and the mechanism by which this reduction occurs.

Results

We demonstrate that FTI-277 significantly inhibits phosphate-induced mineral deposition by vascular smooth muscle cells (VSMC) in vitro, prevents VSMC osteogenic differentiation, and increases mRNA expression of matrix Gla protein (MGP), an inhibitor of mineralization. FTI-277 increases Akt signaling in VSMC in short-term serum-stimulation assays and in long-term mineralization assays. In contrast, manumycin A has no effect on Akt signaling or mineralization. Co-incubation of VSMC with FTI-277 and SH6 (an Akt inhibitor) significantly reduces the inhibitory effect of FTI-277 on mineralization, demonstrating that FTI-277 inhibits calcification by activating Akt signaling. Over-expression of the constitutively active p110 sub-unit of PI3K in VSMC using adenovirus activates Akt, inhibits mineralization, suppresses VSMC differentiation and significantly enhances MGP mRNA expression. FTI-277 also inhibits phosphate-induced activation of caspase 3 and apoptosis of VSMC, and these effects are negated by co-incubation with SH6. Finally, using an ex vivo model of vascular calcification, we demonstrate that FTI-277 inhibits high phosphate-induced mineralization in aortic rings derived from rats with end-stage renal failure.

Conclusions

Together, these results demonstrate that FTI-277 inhibits VSMC mineral deposition by up-regulating PI3K/Akt signaling and preventing apoptosis, suggesting that targeting farnesylation, or Akt specifically, may have therapeutic potential for the prevention of vascular calcification.

Omega-3 fatty acid DHA modulates p53, survivin, and microRNA-16-1 expression in KRAS-mutant colorectal cancer stem-like cells

Background

The presence of chemotherapy-resistant colorectal cancer stem cells (CCSCs) with KRAS mutation is thought to be one of the primary causes for treatment failure in colorectal cancer (CRC). P53, survivin, and microRNA-16-1 are challenging targets for anticancer drugs which are associated with chemoresistance in CRC. Yet, no p53-, survivin-, and microRNA-16-1-modulating drug with low toxicity but high efficacy against KRAS-mutant CCSCs have been approved for clinical application in CRC. Here, we investigated whether in vitro concentrations of DHA equal to human plasma levels, are able to modulate, Wt-p53, survivin, and microRNA-16-1 in CRC cells with stem cell-like properties.

Methods

Wt-p53/KRAS-mutant CRC cells (HCT-116) with stem cell-like properties were treated with 100-, 150- and 200-μM/L DHA, after which cell number, viability, growth inhibition, Wt-p53, survivin and microRNA-16-1 expression, caspase-3 activation and apoptotic-rate were evaluated by different cellular and molecular techniques.

Results

After 24-, 48-, and 72-h treatments with 100- to 200-μM/L DHA, growth inhibition- rates were measured to be 54.7% to 59.7%, 73.% to 75.8%, and 63.3% to 97.7%, respectively. Treatment for 48 h with indicated DHA concentrations decreased cell number and viability. In addition, we observed a decrease in both the transcript and protein levels of survivin followed by 1.3- to 1.7- and 1.1- to 4.7-fold increases in the Wt-p53 accumulation and caspase-3 activation levels respectively. Treatment with 100 and 150 μM/L DHA increased microRNA-16-1 expression levels by 1.3- to 1.7-fold and enhanced the microRNA-16-1/survivin mRNA, p53/survivin, and caspase-3/survivin protein ratios by 1.7- to 1.8-, 1.3- to 2.6-, and 1.3- to 2-fold increases respectively. A decrease in the number of live cells and an increase in the number of apoptotic cells were also observed with increasing DHA concentrations.

Conclusion

Wt-p53, survivin, and microRNA-16-1 appear to be promising molecular targets of DHA. Thus, DHA might represent an attractive anti-tumor agent directed against KRAS-mutant CCSCs.

Type I insulin-like growth factor receptor signaling in hematological malignancies

The insulin-like growth factor (IGF) signaling system plays key roles in the establishment and progression of different types of cancer. In agreement with this idea, substantial evidence has shown that the type I IGF receptor (IGF-IR) and its primary ligand IGF-I are important for maintaining the survival of malignant cells of hematopoietic origin. In this review, we discuss current understanding of the role of IGF-IR signaling in cancer with a focus on the hematological neoplasms. We also address the emergence of IGF-IR as a potential therapeutic target for the treatment of different types of cancer including plasma cell myeloma, leukemia, and lymphoma.

Targeting survivin with prodigiosin isolated from cell wall of Serratia marcescens induces apoptosis in hepatocellular carcinoma cells

BACKGROUND

Abnormal activation of the Wnt/β-catenin signaling pathway increases survivin expression that is involved in hepatocarcinogenesis. Therefore, downregulation of survivin may provide an attractive strategy for treatment of hepatocellular carcinoma. In this regard, little is known about the anticancer effects of prodigiosin isolated from cell wall of Serratia marcescens on the survivin expression and induction of apoptosis in hepatocellular carcinoma cells.

METHODS

Human hepatocellular carcinoma (HepG2) cells were treated with 100-, 200-, 400-, and 600-nM prodigiosin after which morphology of cells, cell number, growth inhibition, survivin expression, caspase-3 activation, and apoptotic rate were evaluated by inverted microscope, hemocytometer, MTT assay, RT-PCR, fluorometric immunosorbent enzyme assay, and flow cytometric analysis, respectively.

RESULTS

Prodigiosin changed morphology of cells to apoptotic forms and disrupted cell connections. This compound significantly increased growth inhibition rate and decreased metabolic activity of HepG2 cells in a dose- and time-dependent manner. After 24-, 48-, and 72-h treatments with prodigiosin at concentrations ranging from 100 nM to 600 nM, growth inhibition rates were measured to be 1.5-10%, 24-47.5%, and 55.5-72.5%, respectively, compared to untreated cells. At the same conditions, metabolic activities were measured to be 91-83%, 74-53%, and 47-31% for indicated concentrations of prodigiosin, respectively, compared to untreated cells. We also found that treatment of HepG2 cells for 48 h decreased significantly cell number and survivin expression and increased caspase-3 activation in a dose-dependent manner. Specifically, treatment with 600-nM prodigiosin resulted in 77% decrease in cell number, 88.5% decrease in survivin messenger RNA level, and 330% increase in caspase-3 activation level compared to untreated cells. An increase in the number of apoptotic cells (late apoptosis) ranging from 36.9% to 97.4% was observed with increasing prodigiosin concentrations.

CONCLUSION

From our data, prodigiosin is an attractive compound that turns the profile of high-level survivin expression in hepatocellular carcinoma cells into that of normal cells and may provide a novel approach to the hepatocellular carcinoma-targeted therapy.

N-Hydroxyphthalimide exhibits antitumor activity by suppressing mTOR signaling pathway in BT-20 and LoVo cells

Background

N-Hydroxyphthalimide (NHPI), an important chemical raw material, was found to have potent and selective anti-proliferative effect on human breast carcinoma BT-20 cells, human colon adenocarcinoma LoVo and HT-29 cells during our screening for anticancer compounds. The purpose of this study is to assess the antitumor efficacy of NHPI in vitro and in vivo and to explore the underlying antitumor mechanism.

Methods

Cell cytotoxicity of NHPI was evaluated using MTS assay and cell morphological analysis. After NHPI treatment, cell cycle, apoptosis and mitochondrial membrane potential were analyzed using flow cytometer. The subcellular localization of eukaryotic initiation factor 4E (eIF4E) was analyzed by immunofluorescence assay. The antitumor efficacy of NHPI in vivo was tested in BT-20 xenografts. The underlying antitumor mechanisms of NHPI in vitro and in vivo were investigated with western blot analysis in NHPI-treated cancer cells and tumor tissues. Statistical significance was determined using Student’s t-test.

Results

In vitro, NHPI selectively inhibited the proliferation and induced G₂/M phase arrest in BT-20 and LoVo cells, which was attributed to the inhibition of cyclin B1 and cdc2 expressions. Furthermore, NHPI induced apoptosis via mitochondrial pathway. Of note, NHPI effectively inhibited mammalian target of rapamycin (mTOR) complex 1 (mTORC1) and mTOR complex 2 (mTORC2) signaling, and overcame the feedback activation of Akt and extracellular signal-regulated kinase (ERK) caused by mTORC1 inhibition in BT-20 and LoVo cells. In vivo, NHPI inhibited tumor growth and suppressed mTORC1 and mTORC2 signaling in BT-20 xenografts with no obvious toxicity.

Conclusions

We found for the first time that NHPI displayed antitumor activity which is associated with the inhibition of mTOR signaling pathway. Our findings suggest that NHPI may be developed as a promising candidate for cancer therapeutics by targeting mTOR signaling pathway and as such warrants further exploration.

BMS-754807 is cytotoxic to non-small cell lung cancer cells and enhances the effects of platinum chemotherapeutics in the human lung cancer cell line A549

Background

Despite advances in targeted therapy for lung cancer, survival for patients remains poor and lung cancer remains the leading cause of cancer-related deaths worldwide. The type I insulin-like growth factor receptor (IGF-IR) has emerged as a potential target for lung cancer treatment, however, clinical trials to date have provided disappointing results. Further research is needed to identify if certain patients would benefit from IGF-IR targeted therapies and the ideal approach to incorporate IGF-IR targeted agents with current therapies.

Methods

The dual IGF-IR/insulin receptor inhibitor, BMS-754807, was evaluated alone and in combination with platinum-based chemotherapeutics in two human non-small cell lung cancer (NSCLC) cell lines. Cell survival was determined using WST-1 assays and drug interaction was evaluated using Calcusyn software. Proliferation and apoptosis were determined using immunofluorescence for phospho-histone H3 and cleaved caspase 3, respectively.

Results

Treatment with BMS-754807 alone reduced cell survival and wound closure while enhancing apoptosis in both human lung cancer cell lines. These effects appear to be mediated through IGF-IR/IR signaling and, at least in part, through the PI3K/AKT pathway as administration of BMS-754807 to A549 or NCI-H358 cells significantly suppressed IGF-IR/IR and AKT phosphorylation. In addition of BMS-754807 enhanced the cytotoxic effects of carboplatin or cisplatin in a synergistic manner when given simultaneously to A549 cells.

Conclusions

BMS-754807 may be an effective therapeutic agent for the treatment of NSCLC, particularly in lung cancer cells expressing high levels of IGF-IR.

Mutation R273H confers p53 a stimulating effect on the IGF-1R-AKT pathway via miR-30a suppression in breast cancer

p53 is the most highly mutated tumor suppressor in human malignancies. A wide array of p53 mutations has been revealed to play pivotal roles during cancer progression, which abolish anti-tumor functions of wild type p53 but also elicit tumorigenic effects by activating a diverse subset of downstream molecules. R273H mutation of p53 has been closely implicated in human cancer. Here we report miR-30a as a novel downstream target of p53 R273H mutant, which binds to the promoter region to repress miR-30a expression. Consequently, p53 R273H mutant enhances the migratory capabilities of tumor cells that are compromised by exogenous miR-30a over-expression. Our further investigation indicates that p53 R273H mutation unleashes the inhibition effect of miR-30a on IGF-1R expression, thus leading to elevated activation of IGF-1R-AKT signaling cascade in tumor cells.

Survivin in survival of hepatocellular carcinoma

Survivin is an anti-apoptotic protein belonging to the inhibitor of apoptosis protein (IAP) family. It is involved in the regulation of important physiological and pathological processes in cells and functions to inhibit cell apoptosis and promote cell proliferation. Normally and terminally differentiated tissues are nearly negative for survivin. In contrast, survivin is highly expressed in most human tumor tissues, including hepatocellular carcinoma (HCC). The abnormal overexpression of survivin is closely related to the malignant biological behaviors of tumors. During the development and progression of HCC, the high level of survivin expression promotes cancer cell proliferation, inhibits cancer cell apoptosis, induces tumor stromal angiogenesis, reduces the sensitivity of cancer cells to radiotherapy and chemotherapy, and ultimately affects the prognosis of patients with HCC. Survivin expression is regulated by a large number of factors. The latest discovery indicated that the transcription factor octamer-binding transcription factor 4 (OCT4) enhances the expression of survivin though cyclin D1 (CCND1), which, in part, accounts for tumor cell proliferation, recurrence and metastasis. Survivin plays key roles in HCC, which renders it an ideal target for the treatment of HCC. The present article reviews the research progress on the relationship between survivin and HCC and on the HCC treatment strategies targeting survivin.

Vorinostat synergizes with ridaforolimus and abrogates the ridaforolimus-induced activation of AKT in synovial sarcoma cells

Background

Curative treatments for patients with metastatic synovial sarcoma (SS) do not exist, and such patients have a poor prognosis. We explored combinations of molecularly-targeted and cytotoxic agents to identify synergistic treatment combinations in SS cells.

Methods

Two SS cell lines (HS-SY-II and SYO-I) were treated with single agents or combinations of molecularly targeted therapies (HDAC inhibitor, vorinostat; mTOR inhibitor, ridaforolimus) and cytotoxic agents. After 72 hours, cell viability was measured using the MTS cell proliferation assay. Combination Indices (CI) were calculated to determine whether each combination was synergistic, additive, or antagonistic. Western Blot analysis assessed alterations in total and phospho-AKT protein levels in response to drug treatment.

Results

We determined the single-agent IC₅₀ for ridaforolimus, vorinostat, doxorubicin, and melphalan in HS-SY-II and SYO-I. Synergism was apparent in cells co-treated with ridaforolimus and vorinostat: CI was 0.28 and 0.63 in HS-SY-II and SYO-I, respectively. Ridaforolimus/doxorubicin and ridaforolimus/melphalan exhibited synergism in both cell lines. An additive effect was observed with combination of vorinostat/doxorubicin in both cell lines. Vorinostat/melphalan was synergistic in HS-SY-II and additive in SYO-I. Western blot analysis demonstrated that ridaforolimus increased pAKT-ser473 levels; this effect was abrogated by vorinostat co-treatment.

Conclusions

The combination of ridaforolimus and vorinostat demonstrates in vitro synergism in SS. Addition of vorinostat abrogated ridaforolimus-induced AKT activation. Since AKT activation is a possible mechanism of resistance to mTOR inhibitors, adding vorinostat (or another HDAC inhibitor) may be a route to circumvent AKT-mediated resistance to mTOR inhibitors.

Management of EGFR-mutant non-small-cell lung cancer patients after first-line reversible EGF receptor-tyrosine kinase inhibitors

SUMMARY Lung cancers harboring mutations in the EGFR respond to EGF receptor-tyrosine kinase inhibitor, which at present represent the most appropriate treatment for EGFR mutation-positive advanced non-small-cell lung cancer. Unfortunately drug resistance invariably emerges with different known mechanisms, including the EGFR T790M mutation, MET gene amplification, EGFR amplification, mutations in the PIK3CA gene, mutations in the HER2 gene, IGF1R amplification, transformation of non-small-cell lung cancer into small-cell lung cancer and moreover epithelial-to-mesenchymal transition. Various strategies to manage secondary resistance have been explored and in this review we will analyze scientific data in support of these different strategies to assess the most adequate to use in relation to the progression disease.

Vertical blockade of the IGFR- PI3K/Akt/mTOR pathway for the treatment of hepatocellular carcinoma: the role of survivin

BACKGROUND

To explore whether combining inhibitors that target the insulin-like growth factor receptor (IGFR)/PI3K/Akt/mTOR signaling pathway (vertical blockade) can improve treatment efficacy for hepatocellular carcinoma (HCC).

METHODS

HCC cell lines (including Hep3B, Huh7, and PLC5) and HUVECs (human umbilical venous endothelial cells) were tested. The molecular targeting therapy agents tested included NVP-AEW541 (IGFR kinase inhibitor), MK2206 (Akt inhibitor), BEZ235 (PI3K/mTOR inhibitor), and RAD001 (mTOR inhibitor). Potential synergistic antitumor effects were tested by median dose-effect analysis in vitro and by xenograft HCC models. Apoptosis was analyzed by flow cytometry (sub-G1 fraction analysis) and Western blotting. The activities of pertinent signaling pathways and expression of apoptosis-related proteins were measured by Western blotting.

RESULTS

Vertical blockade induced a more sustained inhibition of PI3K/Akt/mTOR signaling activities in all the HCC cells and HUVEC tested. Synergistic apoptosis-inducing effects, however, varied among different cell lines and drug combinations and were most prominent when NVP-AEW541 was combined with MK2206. Using an apoptosis array, we identified survivin as a potential downstream mediator. Over-expression of survivin in HCC cells abolished the anti-tumor synergy between NVP-AEW541 and MK2206, whereas knockdown of survivin improved the anti-tumor effects of all drug combinations tested. In vivo by xenograft studies confirmed the anti-tumor synergy between NVP-AEW541 and MK2206 and exhibited acceptable toxicity profiles.

CONCLUSIONS

Vertical blockade of the IGFR/PI3K/Akt/mTOR pathway has promising anti-tumor activity for HCC. Survivin expression may serve as a biomarker to predict treatment efficacy.

Function of survivin in trophoblastic cells of the placenta

BACKGROUND

Preeclampsia is one of the leading causes of maternal and perinatal mortality and morbidity worldwide and its pathogenesis is not totally understood. As a member of the chromosomal passenger complex and an inhibitor of apoptosis, survivin is a well-characterized oncoprotein. Its roles in trophoblastic cells remain to be defined.

METHODS

The placental samples from 16 preeclampsia patients and 16 well-matched controls were included in this study. Real-time PCR, immunohistochemistry and Western blot analysis were carried out with placental tissues. Primary trophoblastic cells from term placentas were isolated for Western blot analysis. Cell proliferation, cell cycle analysis and immunofluorescence staining were performed in trophoblastic cell lines BeWo, JAR and HTR-8/SVneo.

RESULTS

The survivin gene is reduced but the protein amount is hardly changed in preeclamptic placentas, compared to control placentas. Upon stress, survivin in trophoblastic cells is phosphorylated on its residue serine 20 by protein kinase A and becomes stabilized, accompanied by increased heat shock protein 90. Depletion of survivin induces chromosome misalignment, abnormal centrosome integrity, and reduced localization and activity of Aurora B at the centromeres/kinetochores in trophoblastic metaphase cells.

CONCLUSIONS

Our data indicate that survivin plays pivotal roles in cell survival and proliferation of trophoblastic cells. Further investigations are required to define the function of survivin in each cell type of the placenta in the context of proliferation, differentiation, apoptosis, angiogenesis, migration and invasion.

Neutral sphingomyelinase 2 modulates cytotoxic effects of protopanaxadiol on different human cancer cells

Background

Some of ginsenosides, root extracts from Panax ginseng, exert cytotoxicity against cancer cells through disruption of membrane subdomains called lipid rafts. Protopanaxadiol (PPD) exhibits the highest cytotoxic effect among 8 ginsenosides which we evaluated for anti-cancer activity. We investigated if PPD disrupts lipid rafts in its cytotoxic effects and also the possible mechanisms.

Methods

Eight ginsenosides were evaluated using different cancer cells and cell viability assays. The potent ginsenoside, PPD was investigated for its roles in lipid raft disruption and downstream pathways to apoptosis of cancer cells. Anti-cancer effects of PPD was also investigated in vivo using mouse xenograft model.

Results

PPD consistently exerts its potent cytotoxicity in 2 cell survival assays using 5 different cancer cell lines. PPD disrupts lipid rafts in different ways from methyl-β-cyclodextrin (MβCD) depleting cholesterol out of the subdomains, since lipid raft proteins were differentially modulated by the saponin. During disruption of lipid rafts, PPD activated neutral sphingomyelinase 2 (nSMase 2) hydrolyzing membrane sphingomyelins into pro-apoptotic intracellular ceramides. Furthermore, PPD demonstrated its anti-cancer activities against K562 tumor cells in mouse xenograft model, confirming its potential as an adjunct or chemotherapeutic agent by itself in vivo.

Conclusions

This study demonstrates that neutral sphingomyelinase 2 is responsible for the cytotoxicity of PPD through production of apoptotic ceramides from membrane sphingomyelins. Thus neutral sphingomyelinase 2 and its relevant mechanisms may potentially be employed in cancer chemotherapies.

A novel antitumor activity of deguelin targeting the insulin-like growth factor (IGF) receptor pathway via up-regulation of IGF-binding protein-3 expression in breast cancer

In this study, we investigated the antitumor effects of deguelin in several human breast cancer cells in vitro and in vivo. Deguelin inhibited cell viability and the anchorage-dependent and anchorage-independent colony formation of triple-negative (MDA-MB-231 and MDA-MB-468) and triple-positive (MCF-7) breast cancer cells, and it significantly reduced the growth of MCF-7 cell xenograft tumors. The induction of apoptosis, inhibition of insulin-like growth factor-1 receptor (IGF-1R) signaling activation, and up-regulation of IGF-binding protein-3 (IGFBP-3) expression may be associated with deguelin-mediated antitumor effects. Our findings suggest a potential therapeutic use for deguelin in patients with triple-negative breast cancer and for those with breast cancers who are sensitive to endocrine- and HER2-targeted therapies.

A multiplicity of anti-invasive effects of farnesyl transferase inhibitor SCH66336 in human head and neck cancer

Metastasis is a critical event in the progression of head and neck squamous cell carcinoma (HNSCC) and closely correlates with clinical outcome. We previously showed that the farnesyl transferase inhibitor SCH66336 has antitumor activities in HNSCC by inducing the secretion of insulin-like growth factor binding protein 3 (IGFBP-3), which in turn inhibits tumor growth and angiogenesis. In our study, we found that SCH66336 at a sublethal dose for HNSCC inhibited the migration and invasion of HNSCC cells. The inhibitory effect of SCH66336 was associated with the blockade of the IGF-1 receptor (IGF-1R) pathway via suppressing IGF-1R itself and Akt expression. Consistent with previous work, induction of IGFBP-3 by SCH66336 also contributed in part to the anti-invasive effect. SCH66336 treatment also reduced the expression and activity of the urokinase-type plasminogen activator (uPA) and matrix metalloproteinase 2 (MMP-2), both important regulators of tumor metastasis. The effect of SCH66336 on uPA activity was inhibited partly by knockdown of IGFBP-3 using small interfering RNA. The inhibitory effect of SCH66336 on migration or invasion was attenuated partly or completely by knockdown of IGFBP-3, Akt or IGF-1R expression, respectively. Our results demonstrate that the IGF-1R pathway plays a major role in the proliferation, migration and invasion of HNSCC cells, suggesting that therapeutic obstruction of the IGF-1R pathway would be a useful approach to treating patients with HNSCC.

Lonafarnib for cancer and progeria

INTRODUCTION

Lonafarnib is a non-peptidomimetic inhibitor of farnesyl transferase, an enzyme responsible for the post-translational lipid modification of a wide variety of cellular proteins that are involved in the pathogenic pathways of various diseases including cancer and progeria. Although extensive clinical research indicates limited activity of lonafarnib in solid tumors, there is recent interest in combinations of farnesyl transferase inhibitors with imatinib or bortezomib in hematological malignancies and to investigate the role of lonafarnib in progeria.

AREAS COVERED

This review examines the in vitro and in vivo pharmacology of lonafarnib and the available clinical data for lonafarnib monotherapy and combination therapy in the treatment of solid and hematological malignancies as well as progeria, using studies identified from the PubMed database supplemented by computerized search of relevant abstracts from major cancer and hematology conferences.

EXPERT OPINION

There is no evidence to support the use of lonafarnib in solid tumors. There is ongoing interest to explore lonafarnib for progeria and to investigate other farnesyl transferase inhibitors for chronic and acute leukemias.

Histone deacetylase inhibitors enhance the apoptotic activity of insulin-like growth factor binding protein-3 by blocking PKC-induced IGFBP-3 degradation

Overexpression of insulin-like growth factor binding protein (IGFBP)-3 induces apoptosis of cancer cells. However, preexisting resistance to IGFBP-3 could limit its antitumor activities. This study characterizes the efficacy and mechanism of the combination of recombinant IGFBP-3 (rIGFBP-3) and HDAC inhibitors to overcome IGFBP-3 resistance in a subset of non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC) cells. The effects of the combination of rIGFBP-3 and a number of HDAC inhibitors on cell proliferation and apoptosis were assessed in vitro and in vivo by using the MTT assay, a flow cytometry-based TUNEL assay, Western blot analyses and the NSCLC xenograft tumor model. Combined treatment with HDAC inhibitors and rIGFBP-3 had synergistic antiproliferative effects accompanied by increased apoptosis rates in a subset of NSCLC and HNSCC cell lines in vitro. Moreover, combined treatment with depsipeptide and rIGFBP-3 completely suppressed tumor growth and increased the apoptosis rate in vivo in H1299 NSCLC xenografts. Evidence suggests that HDAC inhibitors increased the half-life of rIGFBP-3 protein by blocking protein kinase C (PKC)-mediated phosphorylation and degradation of rIGFBP-3. In addition, combined treatment of IGFBP-3 with an HDAC inhibitor facilitates apoptosis through upregulation of rIGFBP-3 stability and Akt signaling inhibition. The ability of HDAC inhibitors to decrease PKC activation may enhance apoptotic activities of rIGFBP-3 in NSCLC cells in vitro and in vivo. These results indicated that combined treatment with HDAC inhibitor and rIGFBP-3 could be an effective treatment strategy for NSCLC and HNSCC with highly activated PKC.

Protein-intrinsic and signaling network-based sources of resistance to EGFR- and ErbB family-targeted therapies in head and neck cancer

Agents targeting EGFR and related ErbB family proteins are valuable therapies for the treatment of many cancers. For some tumor types, including squamous cell carcinomas of the head and neck (SCCHN), antibodies targeting EGFR were the first protein-directed agents to show clinical benefit, and remain a standard component of clinical strategies for management of the disease. Nevertheless, many patients display either intrinsic or acquired resistance to these drugs; hence, major research goals are to better understand the underlying causes of resistance, and to develop new therapeutic strategies that boost the impact of EGFR/ErbB inhibitors. In this review, we first summarize current standard use of EGFR inhibitors in the context of SCCHN, and described new agents targeting EGFR currently moving through pre-clinical and clinical development. We then discuss how changes in other transmembrane receptors, including IGF1R, c-Met, and TGF-β, can confer resistance to EGFR-targeted inhibitors, and discuss new agents targeting these proteins. Moving downstream, we discuss critical EGFR-dependent effectors, including PLC-γ; PI3K and PTEN; SHC, GRB2, and RAS and the STAT proteins, as factors in resistance to EGFR-directed inhibitors and as alternative targets of therapeutic inhibition. We summarize alternative sources of resistance among cellular changes that target EGFR itself, through regulation of ligand availability, post-translational modification of EGFR, availability of EGFR partners for hetero-dimerization and control of EGFR intracellular trafficking for recycling versus degradation. Finally, we discuss new strategies to identify effective therapeutic combinations involving EGFR-targeted inhibitors, in the context of new system level data becoming available for analysis of individual tumors.

Targeting protein prenylation for cancer therapy

Protein farnesylation and geranylgeranylation, together referred to as prenylation, are lipid post-translational modifications that are required for the transforming activity of many oncogenic proteins, including some RAS family members. This observation prompted the development of inhibitors of farnesyltransferase (FT) and geranylgeranyl-transferase 1 (GGT1) as potential anticancer drugs. In this Review, we discuss the mechanisms by which FT and GGT1 inhibitors (FTIs and GGTIs, respectively) affect signal transduction pathways, cell cycle progression, proliferation and cell survival. In contrast to their preclinical efficacy, only a small subset of patients responds to FTIs. Identifying tumours that depend on farnesylation for survival remains a challenge, and strategies to overcome this are discussed. One GGTI has recently entered the clinic, and the safety and efficacy of GGTIs await results from clinical trials.

Combination of farnesyltransferase and Akt inhibitors is synergistic in breast cancer cells and causes significant breast tumor regression in ErbB2 transgenic mice

The Akt activation inhibitor triciribine and the farnesyltransferase inhibitor tipifarnib have modest to little activity in clinical trials when used as single agents. In this article, preclinical data show that the combination is more effective than single agents both in cultured cells and in vivo. Combination index data analysis shows that this combination is highly synergistic at inhibiting anchorage-dependent growth of breast cancer cells. This synergistic interaction is also observed with structurally unrelated inhibitors of Akt (MK-2206) and farnesyltransferase (FTI-2153). The triciribine/tipifarnib synergistic effects are seen with several cancer cell lines including those from breast, leukemia, multiple myeloma and lung tumors with different genetic alterations such as K-Ras, B-Raf, PI3K (phosphoinositide 3-kinase), p53 and pRb mutations, PTEN, pRB and Ink4a deletions, and ErbB receptor overexpression. Furthermore, the combination is synergistic at inhibiting anchorage-independent growth and at inducing apoptosis in breast cancer cells. The combination is also more effective at inhibiting the Akt/mTOR/S6 kinase pathway. In an ErbB2-driven breast tumor transgenic mouse model, the combination, but not single agent, treatment with triciribine and tipifarnib induces significant breast tumor regression. Our findings warrant further investigation of the combination of farnesyltransferase and Akt inhibitors.

Rapamycin decreases survivin expression to induce NSCLC cell apoptosis under hypoxia through inhibiting HIF-1α induction

Survivin is a member of the inhibitor of apoptosis protein family that is overexpressed in various tumors and is important in restricting apoptosis. Understanding the molecular events of apoptosis may provide information for developing novel therapeutic agents targeting non-small cell lung cancer (NSCLCs). This study used three human NSCLC cell lines, NCI-H1299, SK-MES-1, and NCI-H460. Changes in apoptosis, the mRNA and protein expression of survivin under normoxia and hypoxia, with or without rapamycin treatment were analyzed. In addition, siRNA and ChIP assay were further applied to demonstrate the role of hypoxia-inducible factor 1 (HIF-1)α in regulating survivin expression regulation under hypoxia during rapamycin induced NSCLC cell apoptosis. Treatment with rapamycin resulted in significantly increased NSCLC cells apoptosis under hypoxia. We demonstrated for the first time that rapamycin inhibited hypoxia-induced survivin expression in NSCLC cell lines. We further demonstrated that HIF-1α participated in hypoxia-induced survivin expression, and that rapamycin inhibited hypoxia-induced HIF-1α expression by enhancing its degradation. The results above collectively showed that rapamycin inhibits HIF-1α-induced survivin expression under hypoxia to induce NSCLC apoptosis.

Antiangiogenic antitumor activities of IGFBP-3 are mediated by IGF-independent suppression of Erk1/2 activation and Egr-1-mediated transcriptional events

Most antiangiogenic therapies currently being evaluated in clinical trials target the vascular endothelial growth factor pathway; however, the tumor vasculature can acquire resistance to vascular endothelial growth factor-targeted therapy by shifting to other angiogenesis mechanisms. Insulin-like growth factor binding protein-3 (IGFBP-3) has been reported to suppress tumor growth and angiogenesis by both IGF-dependent and IGF-independent mechanisms; however, understanding of its IGF-independent mechanisms is limited. We observed that IGFBP-3 blocked tumor angiogenesis and growth in non-small cell lung cancer and head and neck squamous cell carcinoma. Conditioned media from an IGFBP-3-treated non-small cell lung cancer cell line displayed a significantly decreased capacity to induce HUVEC proliferation and aortic sprouting. In cancer cells, IGFBP-3 directly interacted with Erk1/2, leading to inactivation of Erk1/2 and Elk-1, and suppressed transcription of early growth response protein 1 and its target genes, basic fibroblast growth factor and platelet-derived growth factor. These data suggest that IGF-independent Erk1/2 inactivation and decreased IGFBP-3-induced Egr-1 expression block the autocrine and paracrine loops of angiogenic factors in vascular endothelial and cancer cells. Together, these findings provide a molecular framework of IGFBP-3's IGF-independent antiangiogenic antitumor activities. Future studies are needed for development of IGFBP-3 as a new line of antiangiogengic cancer drug.

Targeting survivin in cancer: the cell-signalling perspective

Survivin, a prominent anticancer target, is ubiquitously expressed in a plethora of cancers and the evolving complexity in functional regulation of survivin is yet to be deciphered. However, pertaining to the recent studies, therapeutic modulation of survivin is critically regulated by interaction with prominent cell-signalling pathways [HIF-1α, HSP90, PI3K/AKT, mTOR, ERK, tumour suppressor genes (p53, PTEN), oncogenes (Bcl-2, Ras)] and a wide range of growth factors (EGFR, VEGF, among others). In our article we discuss, in detail, an overview of the recent developments in the pharmacological modulation of survivin via cell-signalling paradigms and antisurvivin therapeutics, along with an outlook on therapeutic management of survivin in drug-resistant cancers.

EGF regulates survivin stability through the Raf-1/ERK pathway in insulin-secreting pancreatic β-cells

Background

Postnatal expansion of the pancreatic β-cell mass is required to maintain glucose homeostasis immediately after birth. This β-cell expansion is regulated by multiple growth factors, including glucose, insulin, insulin-like growth factor (IGF-1) and epidermal growth factor (EGF). These mitogens signal through several downstream pathways (AKT, ERK, STAT3, and JNK) to regulate the survival and proliferation of β-cells. Survivin, an oncofetal protein with both pro-proliferative and anti-apoptotic properties, is a known transcriptional target of both IGF-1 and EGF in cancer cells. Here, we analyzed the effects of the β-cell mitogens IGF-1 and EGF on survivin regulation in the established pancreatic β-cell model cell lines, MIN6 and INS-1 and in primary mouse islets.

Results

In pancreatic β-cells, treatment with glucose, insulin, or EGF increased survivin protein levels at early time points. By contrast, no significant effects on survivin were observed following IGF-1 treatment. EGF-stimulated increases in survivin protein were abrogated in the presence of downstream inhibitors of the Raf-1/MEK/ERK pathway. EGF had no significant effect on survivin transcription however it prolonged the half-life of the survivin protein and stabilized survivin protein levels by inhibiting surviving ubiquitination.

Conclusions

This study defines a novel mechanism of survivin regulation by EGF through the Raf-1/MEK/ERK pathway in pancreatic β-cells, via prolongation of survivin protein half-life and inhibition of the ubiquitin-mediated proteasomal degradation pathway. This mechanism may be important for regulating β-cell expansion after birth.

The rationale and development of therapeutic insulin-like growth factor axis inhibition for lung and other cancers

The insulin-like growth factor (IGF) axis involves elements of endocrine, paracrine, and autocrine control. It is centrally involved in normal development and growth. Core signaling is driven through the IGF-1 receptor (IGF-1R) in either homo-multimeric complexes or hetero-multimeric complexes with the insulin receptor (IR). Signaling is affected by a large number of upstream and downstream factors, including the differential expression of various intracellular IR substrates, a range of stimulatory ligands (insulin, IGF-1, and IGF-2), the expression of specific clearance receptors (eg, IGF-2R), and different IGF-binding proteins. Considerable evidence exists to implicate aspects of the IGF axis in the development and maintenance of many different nonneoplastic and neoplastic diseases, including both small-cell lung cancer and non-small-cell lung cancer (NSCLC). A large number of different anticancer strategies directed against the IGF axis are being developed. Monoclonal antibodies directed against the IGF-1R are the furthest advanced clinically. Hyperglycemia appears to be a class effect. To date, the major difference among the antibodies used in clinical trials seems to be their plasma half-lives, leading to a number of different administration regimens being taken forward. Early signals of monotherapy activity have been notably reported in patients with Ewing sarcoma and in several other cancers. Encouraging increases in the NSCLC response rate have already been reported after the addition of an anti-IGF-1R antibody to first-line carboplatin and paclitaxel. Explorations of aspects of ligands, binding proteins, receptors, and receptor substrates are all ongoing to identify potential biomarkers predictive of benefit from IGF axis intervention.

The molecular pathogenesis of head and neck cancer

Head and neck cancer arises from a series of molecular alterations progressive from dysplasia to carcinoma in situ, and finally invasive carcinoma. Risk factors associated with head and neck cancer include tobacco, alcohol and viral infection. There are genetic alterations in pre-cancerous cells that contribute to transformation. The accumulation of these alterations facilitates tumor development. Additionally, the tumor microenvironment enables tumor progression. The cooperative effect of molecular alterations in the tumor cells and compensatory microenvironment changes enable tumors to invade and metastasize. This review focuses on the genes and molecules altered during the progression of head and neck cancer with an emphasis on the genetic, molecular and phenotypic changes during the pathogenesis of head and neck cancer. Therapeutic strategies that target key changes in the tumor cells and/or stromal cells in the tumor microenvironment are discussed.

Rapamycin selectively reduces the association of transcripts containing complex 5' UTRs with ribosomes in C4-2B prostate cancer cells

mTOR pathway inhibitors, specifically rapamycin and its derivatives, are promising therapeutics that targets downstream pathways including protein translation. We examined the effects of a series of inhibitors targeting various pathways on ribosomal polysome distribution, overall translation rates, and translation of specific mRNAs in the bone derived prostate cancer cell line, C4-2B. Treatment with either rapamycin, PD98059 or LY294002 failed to change the distribution of polysomes in sucrose gradients. Although no change in the accumulation of heavy polysomes was observed, there was an overall decrease in the rate of translation caused by treatment with rapamycin or LY294002. Inhibiting the MAPK pathway with PD98059 decreased overall translation by 20%, but had no effect on mRNAs containing a 5' terminal oligopyrimidine tract (TOP) sequences or those with complex 5' UTRs. In contrast, treatment with rapamycin for 24 h reduced overall translation by approximately 45% and affected the translation of mRNAs with complex 5' UTRs, specifically VEGF and HIF1alpha. After 24 h, LY294002 treatment alone decreased overall translation by 60%, more than was observed with rapamycin. Although LY294002 and similar inhibitors are effective at blocking prostate cancer cell growth, they act upstream of AKT and PTEN and cancer cells can find a way to bypass this inhibition. Thus, we propose that inhibiting downstream targets such as mTOR or targets of mTOR will provide rational approaches to developing new combination therapies focused on reducing growth of prostate cancer after arrival in the bone environment.

Inhibition of hypoxia-inducible factor-1 function enhances the sensitivity of multiple myeloma cells to melphalan

Abnormal activation of hypoxia-inducible factor-1 (HIF-1), one of the most important transcription factors for the adaptation of cells to hypoxia, is frequently observed in numerous types of solid tumors. Dysregulation of HIF-1 induces tumor angiogenesis and enhances the expression of anti-apoptotic proteins and glycolysis-associated enzymes in cancer cells, which in turn leads to the promotion of tumor growth. In the present study, we examined the pathophysiologic role of HIF-1 in multiple myeloma. Furthermore, we explored the possibility that HIF-1 may be a molecular target for myeloma therapy. We identified constitutive expression of the hypoxia-inducible factor-1 alpha (HIF-1alpha)-subunit in established myeloma cell lines and in primary myeloma cells. Treatment with insulin-like growth factor-1 (IGF-1) significantly increased HIF-1alpha expression through activation of the AKT and mitogen-activated protein kinase signaling pathways. Inhibition of HIF-1 function either by echinomycin, a specific HIF-1 inhibitor, or a siRNA against HIF-1alpha resulted in enhanced sensitivity to melphalan in myeloma cells. This inhibition of HIF-1 also reversed the protective effect of IGF-1 on melphalan-induced apoptosis. Inhibition of HIF-1 drastically reduced both basal and IGF-1-induced expression of survivin, one of the most important anti-apoptotic proteins in myeloma cells. We conclude that HIF-1 inhibition may be an attractive therapeutic strategy for multiple myeloma.

Insulin-like growth factor-I receptor tyrosine kinase inhibitor cyclolignan picropodophyllin inhibits proliferation and induces apoptosis in multidrug resistant osteosarcoma cell lines

Insulin-like growth factor-I receptor (IGF-IR) is an important mediator of tumor cell survival and shows prognostic significance in sarcoma. To explore potential therapeutic strategies for interrupting signaling through this pathway, we assessed the ability of cyclolignan picropodophyllin (PPP), a member of the cyclolignan family, to selectively inhibit the receptor tyrosine kinase activity of IGF-IR in several sarcoma cell line model systems. Of the diverse sarcoma subtypes studied, osteosarcoma cell lines were found to be particularly sensitive to IGF-IR inhibition, including several multidrug resistant osteosarcoma cell lines with documented resistance to various conventional anticancer drugs. PPP shows relatively little toxicity in human osteoblast cell lines when compared with osteosarcoma cell lines. These studies show that PPP significantly inhibits IGF-IR expression and activation in both chemotherapy-sensitive and chemotherapy-resistant osteosarcoma cell lines. This inhibition of the IGF-IR pathway correlates with suppression of proliferation of osteosarcoma cell lines and with apoptosis induction as measured by monitoring of poly(ADP-ribose) polymerase and its cleavage product and by quantitative measurement of apoptosis-associated CK18Asp396. Importantly, PPP increases the cytotoxic effects of doxorubicin in doxorubicin-resistant osteosarcoma cell lines U-2OS(MR) and KHOS(MR). Furthermore, small interfering RNA down-regulation of IGF-IR expression in drug-resistant cell lines also caused resensitization to doxorubicin. Our data suggest that inhibition of IGF-IR with PPP offers a novel and selective therapeutic strategy for ostosarcoma, and at the same time, PPP is effective at reversing the drug-resistant phenotype in osteosarcoma cell lines.

New wirings in the survivin networks

A little over 10 years after its discovery in 1997, the small inhibitor of apoptosis (IAP) protein, survivin, continues to generate intense interest and keen attention from disparate segments of basic and disease-related research. Part of this interest reflects the intricate biology of this multifunctional protein that intersects fundamental networks of cellular homeostasis. Part is because of the role of survivin as a cancer gene, which touches nearly every aspect of the disease, from onset to outcome. And part is due to the potential value of survivin for novel cancer diagnostics and therapeutics, which have already reached the clinic, and with some promise. Grappling with emerging new signaling circuits in survivin biology, and their implications in cancer, will further our understanding of this nodal protein, and open fresh opportunities for translational oncology research.