Inhibitors of mTOR overcome drug resistance from topoisomerase II inhibitors in solid tumors

PI3K/Akt/mTOR Pathway and Its Role in Cancer Therapeutics: Are We Making Headway?

Cancer is a severe public health issue that is a leading cause of mortality globally. It is also an impediment to improving life expectancy worldwide. Furthermore, the global burden of cancer incidence and death is continuously growing. Current therapeutic options are insufficient for patients, and tumor complexity and heterogeneity necessitate customized medicine or targeted therapy. It is critical to identify potential cancer therapeutic targets. Aberrant activation of the PI3K/AKT/mTOR pathway has a significant role in carcinogenesis. This review summarized oncogenic PI3K/Akt/mTOR pathway alterations in cancer and various cancer hallmarks associated with the PI3K/AKT/mTOR pathway, such as cell proliferation, autophagy, apoptosis, angiogenesis, epithelial-to-mesenchymal transition (EMT), and chemoresistance. Importantly, this review provided recent advances in PI3K/AKT/mTOR inhibitor research. Overall, an in-depth understanding of the association between the PI3K/AKT/mTOR pathway and tumorigenesis and the development of therapies targeting the PI3K/AKT/mTOR pathway will help make clinical decisions.

Rationally designed rapamycin-encapsulated ZIF-8 nanosystem for overcoming chemotherapy resistance

Zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are widely reported as a pH-sensitive drug delivery carrier with high loading capacity for tumor therapy. However, the mechanism of intracellular corrosion of ZIF-8 and the corresponding biological effects especially for autophagy response have been rarely reported. Herein, the as-synthesized ZIF-8 was demonstrated to induce mTOR independent and pro-death autophagy. Interestingly, the autophagic process participated in the corrosion of ZIF-8. Subsequently, zinc ion release and the generation of reactive oxygen species due to its corrosion in the acidic compartments were directly responsible for tumor cell killing. In addition, ZIF-8 could sensitize tumor cells to chemotherapy by switching cytoprotective to death promoting autophagy induced by doxorubicin. The mTOR signaling pathway activation was demonstrated to restrict tumor chemotherapy efficiency. Hence, a combined platform rapamycin encapsulated zeolitic imidazolate frameworks (Rapa@ZIF-8) was constructed and demonstrated a more significant chemo-sensitized effect relative to ZIF-8 nanoparticles or rapamycin treatment alone. Lastly, the combined administration of Rapa@ZIF-8 and doxorubicin exhibited an outstanding synergistic antitumor effect without any obvious toxicity to the major organs of mice. Collectively, the optimized nanoplatform, Rapa@ZIF-8, provides a proof of concept for intentionally interfering mTOR pathway and utilizing the switch of survival-to death-promoting autophagy for adjunct chemotherapy.

Small Nucleolar RNAs Determine Resistance to Doxorubicin in Human Osteosarcoma

Doxorubicin (Dox) is one of the most important first-line drugs used in osteosarcoma therapy. Multiple and not fully clarified mechanisms, however, determine resistance to Dox. With the aim of identifying new markers associated with Dox-resistance, we found a global up-regulation of small nucleolar RNAs (snoRNAs) in human Dox-resistant osteosarcoma cells. We investigated if and how snoRNAs are linked to resistance. After RT-PCR validation of snoRNAs up-regulated in osteosarcoma cells with different degrees of resistance to Dox, we overexpressed them in Dox-sensitive cells. We then evaluated Dox cytotoxicity and changes in genes relevant for osteosarcoma pathogenesis by PCR arrays. SNORD3A, SNORA13 and SNORA28 reduced Dox-cytotoxicity when over-expressed in Dox-sensitive cells. In these cells, GADD45A and MYC were up-regulated, TOP2A was down-regulated. The same profile was detected in cells with acquired resistance to Dox. GADD45A/MYC-silencing and TOP2A-over-expression counteracted the resistance to Dox induced by snoRNAs. We reported for the first time that snoRNAs induce resistance to Dox in human osteosarcoma, by modulating the expression of genes involved in DNA damaging sensing, DNA repair, ribosome biogenesis, and proliferation. Targeting snoRNAs or down-stream genes may open new treatment perspectives in chemoresistant osteosarcomas.

Effect of Monoamine oxidase A (MAOA) inhibitors on androgen-sensitive and castration-resistant prostate cancer cells

BACKGROUND

Monoamine oxidase A (MAOA) is best known for its role in neuro-transmitter regulation. Monoamine oxidase inhibitors are used to treat atypical depression. MAOA is highly expressed in high grade prostate cancer and modulates tumorigenesis and progression in prostate cancer. Here, we investigated the potential role of MAOA inhibitors (MAOAIs) in relation to the androgen receptor (AR) pathway and resistance to antiandrogen treatment in prostate cancer.

METHODS

We examined MAOA expression and the effect of MAOI treatment in relation to AR-targeted treatments using the LNCaP, C4-2B, and 22Rv1 human prostate cancer cell lines. MAOA, AR-full length (AR-FL), AR splice variant 7 (AR-V7), and PSA expression was evaluated in the presence of MAOAIs (clorgyline, phenelzine), androgenic ligand (R1881), and antiandrogen (enzalutamide) treatments. An enzalutamide resistance cell line was generated to test the effect of MAOAI treatment in this model.

RESULTS

We observed that MAOAIs, particularly clorgyline and phenelzine, were effective at decreasing MAOA activity in human prostate cancer cells. MAOAIs significantly decreased growth of LNCaP, C4-2B, and 22Rv1 cells and produced additive growth inhibitory effects when combined with enzalutamide. Clorgyline decreased expression of AR-FL and AR-V7 in 22Rv1 cells and was effective at decreasing growth of an enzalutamide-resistant C4-2B cell line with increased AR-V7 expression.

CONCLUSIONS

MAOAIs decrease growth and proliferation of androgen-sensitive and castration-resistant prostate cancer cells. Clorgyline, in particular, decreases expression of AR-FL and AR-V7 expression and decreases growth of an enzalutamide-resistant cell line. These findings provide preclinical validation of MAOA inhibitors either alone or in combination with antiandrogens for therapeutic intent in patients with advanced forms of prostate cancer.

Mechanisms of drug resistance in acute myeloid leukemia

Acute myeloid leukemia (AML) is a kind of malignant hematopoietic system disease characterized by abnormal proliferation, poor cell differentiation, and infiltration of bone marrow, peripheral blood, or other tissues. To date, the first-line treatment of AML is still based on daunorubicin and cytosine arabinoside or idarubicin and cytosine arabinoside regimen. However, the complete remission rate of AML is still not optimistic, especially in elderly patients, and the recurrence rate after complete remission is still high. The resistance of leukemia cells to chemotherapy drugs becomes the main obstacle in the treatment of AML. At present, the research on the mechanisms of drug resistance in AML is very active. This article will elaborate on the main mechanisms of drug resistance currently being studied, including drug resistance-related proteins and enzymes, gene alterations, micro RNAs, and signal pathways.

Targeting urothelial carcinoma cells by combining cisplatin with a specific inhibitor of the autophagy-inducing class III PtdIns3K complex

BACKGROUND

Cisplatin-based regimens are routinely employed for the treatment of urothelial carcinoma. However, therapeutic success is hampered by the primary presence of or the development of cisplatin resistance. This chemoresistance is executed by multiple cellular pathways. In recent years, the cellular process of autophagy has been identified as a prosurvival pathway of cancer cells. On the one hand, autophagy enables cancer cells to survive conditions of low oxygen or nutrient supply, frequently found in tumors. On the other hand, autophagy supports chemoresistance of cancer cells. Here, we aimed at investigating the involvement of autophagy for cisplatin resistance in different urothelial carcinoma cell lines.

MATERIALS & METHODS

We analyzed the expression levels of different autophagy-related proteins in cisplatin-sensitive and cisplatin-resistant urothelial carcinoma cell lines. Furthermore, we performed cell viability assays and caspase activity assays with cells treated with cisplatin, non-specific or specific autophagy inhibitors (chloroquine, 3-methyladenine, SAR405) or combinations thereof.

RESULTS

We found that autophagy-related proteins are up-regulated in different cisplatin-resistant urothelial carcinoma cells compared to the sensitive parental cell lines. Furthermore, inhibition of autophagy, in general, or of the autophagy-inducing class III PtdIns3K complex, in particular, sensitized both sensitive and resistant urothelial carcinoma cells to cisplatin-induced cytotoxic effects.

CONCLUSION

We propose that targeting the autophagic machinery might represent a suitable approach to complement or even increase cisplatin efficacy in order to overcome cisplatin resistance in urothelial carcinoma.

MiR-497 decreases cisplatin resistance in ovarian cancer cells by targeting mTOR/P70S6K1

The mechanism of cisplatin resistance in ovarian cancer is not clearly understood. In the present investigation, we found that the expression levels of miR-497 were reduced in chemotherapy-resistant ovarian cancer cells and tumor tissues due to hypermethylation of miR-497 promoter. Low miR-497 expression levels were associated with chemo-resistant phonotype of ovarian cancer. By analyzing the expression levels of miR-497, mTOR and p70S6K1 in a clinical gene-expression array dataset, we found that mTOR and p70S6K1, two proteins correlated to chemotherapy-resistance in multiple types of human cancers, were inversely correlated with miR-497 levels in ovarian cancer tissues. By using an orthotopic ovarian tumor model and a Tet-On inducible miR-497 expression system, our results demonstrated that overexpression of miR-497 sensitizes the resistant ovarian tumor to cisplatin treatment. Therefore, we suggest that miR-497 might be used as a therapeutic supplement to increase ovarian cancer treatment response to cisplatin.

Cryptolepine derivative-6h inhibits liver fibrosis in TGF-β1-induced HSC-T6 cells by targeting the Shh pathway

Liver fibrosis is a worldwide problem with a significant morbidity and mortality. Cryptolepis sanguinolenta (family Periplocaceae) is widely used in West African countries for the treatment of malaria, as well as for some other diseases. However, the role of C. sanguinolenta in hepatic fibrosis is still unknown. It has been reported that Methyl-CpG binding protein 2 (MeCP2) had a high expression in liver fibrosis and played a central role in its pathobiology. Interestingly, we found that a cryptolepine derivative (HZ-6h) could inhibit liver fibrosis by reducing MeCP2 expression, as evidenced by the dramatic downregulation of α-smooth muscle actin (α-SMA) and type I collagen alpha-1 (Col1α1) in protein levels in vitro. Meanwhile, we also found that HZ-6h could reduce the cell viability and promote apoptosis of hepatic stellate cells (HSCs) treated with transforming growth factor beta 1(TGF-β1). Then, we investigated the potential molecular mechanisms and found that HZ-6h blocked Shh signaling in HSC-T6 cells, resulting in the decreased protein expression of Patched-1 (PTCH-1), Sonic hedgehog (Shh), and glioma-associated oncogene homolog 1 (GLI1). In short, these results indicate that HZ-6h inhibits liver fibrosis by downregulating MeCP2 through the Shh pathway in TGF-β1-induced HSC-T6 cells.

Downregulation of ATG14 by EGR1-MIR152 sensitizes ovarian cancer cells to cisplatin-induced apoptosis by inhibiting cyto-protective autophagy

Cisplatin is commonly used in ovarian cancer treatment by inducing apoptosis in cancer cells as a result of lethal DNA damage. However, the intrinsic and acquired resistance to cisplatin in cancer cells remains a big challenge for improving overall survival. The cyto-protective functions of autophagy in cancer cells have been suggested as a potential mechanism for chemoresistance. Here, we reported MIR152 as a new autophagy-regulating miRNA that plays a role in cisplatin-resistance. We showed that MIR152 expression was dramatically downregulated in the cisplatin-resistant cell lines A2780/CP70, SKOV3/DDP compared with their respective parental cells, and in ovarian cancer tissues associated with cisplatin-resistance. Overexpression of MIR152 sensitized cisplatin-resistant ovarian cancer cells by reducing cisplatin-induced autophagy, enhancing cisplatin-induced apoptosis and inhibition of cell proliferation. A mouse subcutaneous xenograft tumor model using A2780/CP70 cells with overexpressing MIR152 was established and displayed decreased tumor growth in response to cisplatin. We also identified that ATG14 is a functional target of MIR152 in regulating autophagy inhibition. Furthermore, we found that EGR1 (early growth response 1) regulated the MIR152 gene at the transcriptional level. Ectopic expression of EGR1 enhanced efficacy of chemotherapy in A2780/CP70 cells. More importantly, these findings were relevant to clinical cases. Both EGR1 and MIR152 expression levels were significantly lower in ovarian cancer tissues with high levels of ERCC1 (excision repair cross-complementation group 1), a marker for cisplatin-resistance. Collectively, these data provide insights into novel mechanisms for acquired cisplatin-resistance. Activation of EGR1 and MIR152 may be a useful therapeutic strategy to overcome cisplatin-resistance by preventing cyto-protective autophagy in ovarian cancer.

Dual fatty acid synthase and HER2 signaling blockade shows marked antitumor activity against breast cancer models resistant to anti-HER2 drugs

Blocking the enzyme Fatty Acid Synthase (FASN) leads to apoptosis of HER2-positive breast carcinoma cells. The hypothesis is that blocking FASN, in combination with anti-HER2 signaling agents, would be an effective antitumor strategy in preclinical HER2+ breast cancer models of trastuzumab and lapatinib resistance. We developed and molecularly characterized in vitro HER2+ models of resistance to trastuzumab (SKTR), lapatinib (SKLR) and both (SKLTR). The cellular interactions of combining anti-FASN polyphenolic compounds (EGCG and the synthetic G28UCM) with anti-HER2 signaling drugs (trastuzumab plus pertuzumab and temsirolimus) were analyzed. Tumor growth inhibition after treatment with EGCG, pertuzumab, temsirolimus or the combination was evaluated in two in vivo orthoxenopatients: one derived from a HER2+ patient and another from a patient who relapsed on trastuzumab and lapatinib-based therapy. SKTR, SKLR and SKLTR showed hyperactivation of EGFR and p-ERK1/2 and PI3KCA mutations. Dual-resistant cells (SKLTR) also showed hyperactivation of HER4 and recovered levels of p-AKT compared with mono-resistant cells. mTOR, p-mTOR and FASN expression remained stable in SKTR, SKLR and SKLTR. In vitro, anti-FASN compounds plus pertuzumab showed synergistic interactions in lapatinib- and dual- resistant cells and improved the results of pertuzumab plus trastuzumab co-treatment. FASN inhibitors combined with temsirolimus displayed the strongest synergistic interactions in resistant cells. In vivo, both orthoxenopatients showed strong response to the antitumor activity of the combination of EGCG with pertuzumab or temsirolimus, without signs of toxicity. We showed that the simultaneous blockade of FASN and HER2 pathways is effective in cells and in breast cancer models refractory to anti-HER2 therapies.

Hormone Resistance in Two MCF-7 Breast Cancer Cell Lines is Associated with Reduced mTOR Signaling, Decreased Glycolysis, and Increased Sensitivity to Cytotoxic Drugs

The mTOR pathway is a key regulator of multiple cellular signaling pathways and is a potential target for therapy. We have previously developed two hormone-resistant sub-lines of the MCF-7 human breast cancer line, designated TamC3 and TamR3, which were characterized by reduced mTOR signaling, reduced cell volume, and resistance to mTOR inhibition. Here, we show that these lines exhibit increased sensitivity to carboplatin, oxaliplatin, 5-fluorouracil, camptothecin, doxorubicin, paclitaxel, docetaxel, and hydrogen peroxide. The mechanisms underlying these changes have not yet been characterized but may include a shift from glycolysis to mitochondrial respiration. If this phenotype is found in clinical hormone-resistant breast cancers, conventional cytotoxic therapy may be a preferred option for treatment.

Reciprocal regulation of autophagy and dNTP pools in human cancer cells

Ribonucleotide reductase (RNR) plays a critical role in catalyzing the biosynthesis and maintaining the intracellular concentration of 4 deoxyribonucleoside triphosphates (dNTPs). Unbalanced or deficient dNTP pools cause serious genotoxic consequences. Autophagy is the process by which cytoplasmic constituents are degraded in lysosomes to maintain cellular homeostasis and bioenergetics. However, the role of autophagy in regulating dNTP pools is not well understood. Herein, we reported that starvation- or rapamycin-induced autophagy was accompanied by a decrease in RNR activity and dNTP pools in human cancer cells. Furthermore, downregulation of the small subunit of RNR (RRM2) by siRNA or treatment with the RNR inhibitor hydroxyurea substantially induced autophagy. Conversely, cancer cells with abundant endogenous intracellular dNTPs or treated with dNTP precursors were less responsive to autophagy induction by rapamycin, suggesting that autophagy and dNTP pool levels are regulated through a negative feedback loop. Lastly, treatment with si-RRM2 caused an increase in MAP1LC3B, ATG5, BECN1, and ATG12 transcript abundance in xenografted Tu212 tumors in vivo. Together, our results revealed a previously unrecognized reciprocal regulation between dNTP pools and autophagy in cancer cells.

A phase I study of pegylated liposomal doxorubicin and temsirolimus in patients with refractory solid malignancies

This study aimed to determine the maximum-tolerated dose and dose-limiting toxicities of pegylated liposomal doxorubicin (PLD) in combination with temsirolimus (T) in patients with refractory solid tumors. Using a standard “3+3” dose escalation design, 23 patients were enrolled in three dosing cohorts in this phase I study. The starting dose level was PLD at 30 mg/m² every 4 weeks and T at 20 mg weekly. Pharmacokinetics (PK) of doxorubicin were evaluated for patients in the expansion cohort. The most common treatment-related adverse events of all grades were mucositis/stomatitis (69.6 %), anorexia (52.2 %), thrombocytopenia (52.2 %), and fatigue (47.8 %). The recommended doses of this combination for phase II studies are 25 mg/m² PLD and 25 mg T. PK analyses suggested increased exposure of doxorubicin in this combination regimen compared to doxorubicin administered as a single agent, possibly due to PK drug interactions. Out of 18 patients evaluable for a treatment response, two had partial responses (PR) (breast cancer and hepatocellular carcinoma) and six had stable disease (SD). Two patients remained on treatment for more than 1 year. The combination of PLD and T is tolerable, and the treatment resulted in clinical benefit. The combination regimen should be further explored in appropriate tumor types.

Dovitinib synergizes with oxaliplatin in suppressing cell proliferation and inducing apoptosis in colorectal cancer cells regardless of RAS-RAF mutation status

Background

Cancer is the result of a multistep process of genomic alterations, including mutations in key regulatory proteins that result in loss of balanced gene expression and subsequent malignant transformation. Throughout the various stages of colorectal carcinoma (CRC), complex genetic alterations occur, of which over-expression of growth factors, such as vascular endothelial growth factor, fibroblast growth factor and platelet-derive growth factor and their corresponding receptor tyrosine kinases, have been shown to correlate with invasiveness, tumor angiogenesis, metastasis, recurrence, and poor prognosis of colorectal cancer. To evaluate the therapeutic effect, we combined Dovitinib, an orally bioavailable, potent inhibitor of class III-V receptor tyrosine kinases with chemotherapeutic drug, oxaliplatin in preclinical models of colon cancer.

Methods

Human colon cancer cells with different RAS-RAF mutation status (HCT-116, HT-29, SW-480, CaCO2 and LS174T) were treated with a combination of Dovitinib and Oxaliplatin at low dosage followed by assays to investigate the effect of the combination on cell proliferation, cell migration, cell apoptosis and signaling pathways involved in molecular mechanism of drug(s). The antitumor effects of either of the drugs were compared to the combination using human colon carcinoma cell line HT-29 xenograft model. Treated vs untreated tumor sections were also compared for proliferation and angiogenesis markers by immunohistochemistry.

Results

The combination of dovitinib and oxaliplatin showed higher in vitro cytotoxicity in colon cell lines irrespective of their RAS-RAF status as compared to either of the drugs alone. Simultaneous inhibition of MAP kinase and AKT pathways and induction of apoptosis via activation of caspases 9/caspases 3 contributed to the synergistic effect of this combination therapy. In the xenograft model, the combination showed a significantly higher antitumor activity. Immunohistochemistry of post treatment tumors showed a significant decrease in proliferation and angiogenesis as compared to either of the treatments alone.

Conclusions

This study demonstrates the synergistic antitumor activity of combination of dovitinib and oxaliplatin against colon cancer with different RAS-RAF status. The combination also showed its antitumor efficacy in a multidrug resistant phenotype xenograft model. This provides a basis for further investigation for its potential in clinical setting for colorectal cancer.

TIMP-1 increases expression and phosphorylation of proteins associated with drug resistance in breast cancer cells

Tissue inhibitor of metalloproteinase 1 (TIMP-1) is a protein with a potential biological role in drug resistance. To elucidate the unknown molecular mechanisms underlying the association between high TIMP-1 levels and increased chemotherapy resistance, we employed SILAC-based quantitative mass spectrometry to analyze global proteome and phosphoproteome differences of MCF-7 breast cancer cells expressing high or low levels of TIMP-1. In TIMP-1 high expressing cells, 312 proteins and 452 phosphorylation sites were up-regulated. Among these were the cancer drug targets topoisomerase 1, 2A, and 2B, which may explain the resistance phenotype to topoisomerase inhibitors that was observed in cells with high TIMP-1 levels. Pathway analysis showed an enrichment of proteins from functional categories such as apoptosis, cell cycle, DNA repair, transcription factors, drug targets and proteins associated with drug resistance or sensitivity, and drug transportation. The NetworKIN algorithm predicted the protein kinases CK2a, CDK1, PLK1, and ATM as likely candidates involved in the hyperphosphorylation of the topoisomerases. Up-regulation of protein and/or phosphorylation levels of topoisomerases in TIMP-1 high expressing cells may be part of the mechanisms by which TIMP-1 confers resistance to treatment with the widely used topoisomerase inhibitors in breast and colorectal cancer.

Regulation of FANCD2 by the mTOR pathway contributes to the resistance of cancer cells to DNA double-strand breaks

Deregulation of the mTOR pathway is closely associated with tumorigenesis. Accordingly, mTOR inhibitors such as rapamycin and mTOR-selective kinase inhibitors have been tested as cancer therapeutic agents. Inhibition of mTOR results in sensitization to DNA-damaging agents; however, the molecular mechanism is not well understood. We found that an mTOR-selective kinase inhibitor, AZD8055, significantly enhanced sensitivity of a pediatric rhabdomyosarcoma xenograft to radiotherapy and sensitized rhabdomyosarcoma cells to the DNA interstrand cross-linker (ICL) melphalan. Sensitization correlated with drug-induced downregulation of a key component of the Fanconi anemia pathway, FANCD2 through mTOR regulation of FANCD2 gene transcripts via mTORC1-S6K1. Importantly, we show that FANCD2 is required for the proper activation of ATM-Chk2 checkpoint in response to ICL and that mTOR signaling promotes ICL-induced ATM-Chk2 checkpoint activation by sustaining FANCD2. In FANCD2-deficient lymphoblasts, FANCD2 is essential to suppress endogenous and induced DNA damage, and FANCD2-deficient cells showed impaired ATM-Chk2 and ATR-Chk1 activation, which was rescued by reintroduction of wild-type FANCD2. Pharmacologic inhibition of PI3K-mTOR-AKT pathway in Rh30 rhabdomyosarcoma cells attenuated ICL-induced activation of ATM, accompanied with the decrease of FANCD2. These data suggest that the mTOR pathway may promote the repair of DNA double-strand breaks by sustaining FANCD2 and provide a novel mechanism of how the Fanconi anemia pathway modulates DNA damage response and repair.

Cisplatin in combination with zoledronic acid: a synergistic effect in triple-negative breast cancer cell lines

Zoledronic acid (ZA) is the most widely used bisphos-phonate to treat cancer-induced bone disease. There is evidence that bisphosphonates have direct antitumor activity and that their combination with anticancer agents can significantly enhance the effect of treatment. We evaluated whether the combination of ZA with different platinum compounds exerts a synergistic effect in breast cancer cell lines and we investigated the mechanisms of action involved. This study was performed on four breast cancer cell lines, MCF-7, SKBR3, MDA-MB-231 and BRC-230, and confirmed on a primary culture obtained from a breast cancer bone metastasis specimen. ZA (50 µM) was administered for 72 h alone or in combination with cisplatin (Cis) or carboplatin. Drug-induced growth inhibition was detected by sulforhodamine B assay, apoptosis and cell cycle regulation were detected by flow cytometry, and protein expression was evaluated by western blot analysis. MCF-7 and SKBR3 showed very low sensitivity to the three drugs tested. The ZA + Cis combination exerted a high antitumor activity in the two triple-negative lines MDA-MB-231 and BRC-230. An important synergistic effect was obtained in MDA-MB-231 and an additive effect was observed in BRC-230. The p21, pMAPK and m-TOR pathways were regulated by this combined treatment, particularly at lower Cis doses. Carboplatin did not show antitumor activity either alone or in combination with ZA. In conclusion, the potential novel treatment schedule identified for triple-negative breast cancer could prove beneficial in view of the limited therapeutic options available for patients and also since the synergism with ZA would enable lower Cis doses to be used, thus reducing toxicity. Although further research in a clinical setting is warranted, our results on cell lines has been confirmed on a human primary bone metastasis culture.

Everolimus combined with cisplatin has a potential role in treatment of urothelial bladder cancer

Cisplatin (CDDP)-based chemotherapy is a commonly treatment for advanced urothelial carcinoma. However, episodes of cisplatin resistance have been referenced. Recently it has been reported that everolimus (RAD001) could have an important role to play in bladder-cancer treatment and that mTOR inhibitors may restore chemosensitivity in resistant tumours. The aim of this study was to assess RAD001 in vitro ability to enhance CDDP cytotoxicity in three human bladder-cancer cell lines. Over the course of 72h, the cells were exposed to different concentrations of CDDP and RAD001, isolated or combined. Treatment with CDDP statistically (P<0.05) decreased cell proliferation in cell lines in a dose-dependent manner. The anti-proliferative activity of CDDP used in combination with RAD001 was statistically significant (P<0.05) in the cell lines at all concentrations tested. RAD001 had a therapeutic effect when used in combination with CDDP and could therefore be a useful anti-cancer drug combination for patients with bladder cancer.

mTOR Pathway and mTOR Inhibitors in Head and Neck Cancer

Head and neck cancer is the sixth most common type of Cancer worldwide. Since conventional treatment regimens are nonselective and are associated with systemic toxicities, intense investigations focus on molecular targeted therapy with high selectivity and low adverse effects. mTOR signaling pathway has been found to be activated in head and neck cancer, making it attractive for targeted therapy. In addition, expression levels of mTOR and downstream targets eIF4E, 4EBP1, S6K1, and S6 are potential diagnostic and prognostic biomarkers for head and neck cancer. mTOR inhibitors, such as rapamycin and its derivatives temsirolimus and everolimus, exhibit inhibitory effects on head and neck cancer in both in vitro cell line model and in vivo xenograft model. A large number of clinical trials have been initiated to evaluate the therapeutic effects of mTOR inhibitors on patients with head and neck cancer. mTOR inhibitor has potential as a single therapeutic agent or in combination with radiation, chemotherapeutic agents, or other targeted therapeutic agents to obtain synergistic repression on head and neck cancer.

C. elegans AMPKs promote survival and arrest germline development during nutrient stress

Mechanisms controlling development, growth, and metabolism are coordinated in response to changes in environmental conditions, enhancing the likelihood of survival to reproductive maturity. Much remains to be learned about the molecular basis underlying environmental influences on these processes. C. elegans larvae enter a developmentally dormant state called L1 diapause when hatched into nutrient-poor conditions. The nematode pten homologue daf-18 is essential for maintenance of survival and germline stem cell quiescence during this period (Fukuyama et al., 2006; Sigmond et al., 2008), but the details of the signaling network(s) in which it functions remain to be elucidated. Here, we report that animals lacking both aak-1 and aak-2, which encode the two catalytic α subunits of AMP-activated protein kinase (AMPK), show reduced viability and failure to maintain mitotic quiescence in germline stem cells during L1 diapause. Furthermore, failure to arrest germline proliferation has a long term consequence; aak double mutants that have experienced L1 diapause develop into sterile adults when returned to food, whereas their continuously fed siblings are fertile. Both aak and daf-18 appear to maintain germline quiescence by inhibiting activity of the common downstream target, TORC1 (TOR Complex 1). In contrast, rescue of the lethality phenotype indicates that aak-2 acts not only in the intestine, as does daf-18, but also in neurons, likely promoting survival by preventing energy deprivation during L1 diapause. These results not only provide evidence that AMPK contributes to survival during L1 diapause in a manner distinct from that by which it controls dauer diapause, but they also suggest that AMPK suppresses TORC1 activity to maintain stem cell quiescence.

Molecular mechanisms of cisplatin resistance

Platinum-based drugs, and in particular cis-diamminedichloroplatinum(II) (best known as cisplatin), are employed for the treatment of a wide array of solid malignancies, including testicular, ovarian, head and neck, colorectal, bladder and lung cancers. Cisplatin exerts anticancer effects via multiple mechanisms, yet its most prominent (and best understood) mode of action involves the generation of DNA lesions followed by the activation of the DNA damage response and the induction of mitochondrial apoptosis. Despite a consistent rate of initial responses, cisplatin treatment often results in the development of chemoresistance, leading to therapeutic failure. An intense research has been conducted during the past 30 years and several mechanisms that account for the cisplatin-resistant phenotype of tumor cells have been described. Here, we provide a systematic discussion of these mechanism by classifying them in alterations (1) that involve steps preceding the binding of cisplatin to DNA (pre-target resistance), (2) that directly relate to DNA-cisplatin adducts (on-target resistance), (3) concerning the lethal signaling pathway(s) elicited by cisplatin-mediated DNA damage (post-target resistance) and (4) affecting molecular circuitries that do not present obvious links with cisplatin-elicited signals (off-target resistance). As in some clinical settings cisplatin constitutes the major therapeutic option, the development of chemosensitization strategies constitute a goal with important clinical implications.