Rapamycin delays growth of Wnt-1 tumors in spite of suppression of host immunity

Liposomal Formulation of a Melphalan Lipophilic Prodrug: Studies of Acute Toxicity, Tolerability, and Antitumor Efficacy

BACKGROUND

Recently we developed a scalable scheme of synthesis of melphalan ester conjugate with 1,2-dioleoyl-sn-glycerol (MlphDG) and a protocol for the fabrication of its lyophilized liposomal formulation.

OBJECTIVE

Herein we compared this new convenient in use formulation of MlphDG with parent drug Alkeran® in rats concerning several toxicological parameters and evaluated its antitumor efficacy in the model of breast cancer in mice.

METHOD

Liposomes of approximately 100 nm in diameter, consisting of egg phosphatidylcholine, soybean phosphatidylinositol, and MlphDG, or placebo liposomes without the drug were produced by extrusion and lyophilized. Alkeran® or liposomes recovered by the addition of water were injected into the tail vein of animals. Clinical examination of rats consisted of detailed inspection of the behavior, general status, and hematological parameters. Mice with transplanted breast cancer WNT-1 were subjected to multiple treatments with the drugs; tumor growth inhibition was assessed, together with cellular immunity parameters.

RESULTS

Liposomes showed approximately two times lower acute toxicity and better tolerability than Alkeran® in terms of behavioral criteria. The toxic effects of liposomes on hemopoiesis were manifested at higher doses than in the case of Alkeran®, proportionally to the difference in LD50 values. The formulation inhibited tumor growth significantly more effectively than Alkeran®, delaying the start of the exponential growth phase and exhibiting no additional toxic effects toward bone marrow.

CONCLUSION

Lower toxicity of the liposomal formulation of MlphDG promises improved quality of life for cancer patients in need of treatment with melphalan. Presumably, the list of indications for melphalan therapy could be extended.

Obesity-Associated Alterations in Inflammation, Epigenetics, and Mammary Tumor Growth Persist in Formerly Obese Mice

Using a murine model of basal-like breast cancer, we tested the hypothesis that chronic obesity, an established breast cancer risk and progression factor in women, induces mammary gland epigenetic reprogramming and increases mammary tumor growth. Moreover, we assessed whether the obesity-induced epigenetic and protumor effects are reversed by weight normalization. Ovariectomized female C57BL/6 mice were fed a control diet or diet-induced obesity (DIO) regimen for 17 weeks, resulting in a normal weight or obese phenotype, respectively. Mice on the DIO regimen were then randomized to continue the DIO diet or were switched to the control diet, resulting in formerly obese (FOb) mice with weights comparable with control mice. At week 24, all mice were orthotopically injected with MMTV-Wnt-1 mouse mammary tumor cells. Mean tumor volume, serum IL6 levels, expression of proinflammatory genes in the mammary fat pad, and mammary DNA methylation profiles were similar in DIO and FOb mice and higher than in controls. Many of the genes found to have obesity-associated hypermethylation in mice were also found to be hypermethylated in the normal breast tissue of obese versus nonobese human subjects, and nearly all of these concordant genes remained hypermethylated after significant weight loss in the FOb mice. Our findings suggest that weight normalization may not be sufficient to reverse the effects of chronic obesity on epigenetic reprogramming and inflammatory signals in the microenvironment that are associated with breast cancer progression. Cancer Prev Res; 9(5); 339-48. ©2016 AACR.

Adenosine A2A receptors intrinsically regulate CD8+ T cells in the tumor microenvironment

Adenosine A(2A) receptor (A(2A)R) blockade enhances innate and adaptive immune responses. However, mouse genetic studies have shown that A(2A)R deletion does not inhibit the growth of all tumor types. In the current study, we showed that growth rates for ectopic melanoma and bladder tumors are increased in Adora2a(-/-) mice within 2 weeks of tumor inoculation. A(2A)R deletion in the host reduced numbers of CD8(+) T cells and effector-memory differentiation of all T cells. To examine intrinsic functions in T cells, we generated mice harboring a T-cell-specific deletion of A(2A)R. In this host strain, tumor-bearing mice displayed increased growth of ectopic melanomas, decreased numbers of tumor-associated T cells, reduced effector-memory differentiation, and reduced antiapoptotic IL7Rα (CD127) expression on antigen-experienced cells. Intratumoral pharmacologic blockade similarly reduced CD8(+) T-cell density within tumors in wild-type hosts. We found that A(2A)R-proficient CD8(+) T cells specific for melanoma cells displayed a relative survival advantage in tumors. Thus, abrogating A(2A)R signaling appeared to reduce IL7R expression, survival, and differentiation of T cells in the tumor microenvironment. One implication of these results is that the antitumor effects of A(2A)R blockade that can be mediated by activation of cytotoxic T cells may be overcome in some tumor microenvironments as a result of impaired T-cell maintenance and effector-memory differentiation. Thus, our findings imply that the efficacious application of A(2A)R inhibitors for cancer immunotherapy may require careful dose optimization to prevent activation-induced T-cell death in tumors.

Rapamycin-Induced apoptosis in HGF-stimulated lens epithelial cells by AKT/mTOR, ERK and JAK2/STAT3 pathways

Hepatocyte growth factor (HGF) induced the proliferation of lens epithelial cells (LECs) and may be a major cause of posterior capsule opacification (PCO), which is the most frequent postoperative complication of cataract surgery. To date, several agents that can block LECs proliferation have been studied, but none have been used in clinic. Recently, accumulating evidence has suggested rapamycin, the inhibitor of mTOR (mammalian target of Rapamycin), was associated with the induction of apoptosis in LECs. The purpose of our study was to investigate the potential effects of rapamycin on HGF-induced LECs and the underlying mechanisms by which rapamycin exerted its actions. Using cell proliferation, cell viability and flow cytometric apoptosis assays, we found that rapamycin potently not only suppressed proliferation but also induced the apoptosis of LECs in a dose-dependent manner under HGF administration. Further investigation of the underlying mechanism using siRNA transfection revealed that rapamycin could promote apoptosis of LECs via inhibiting HGF-induced phosphorylation of AKT/mTOR, ERK and JAK2/STAT3 signaling molecules. Moreover, the forced expression of AKT, ERK and STAT3 could induce a significant suppression of apoptosis in these cells after treatment of rapamycin. Together, these findings suggested that rapamycin-induced apoptosis in HGF-stimulated LECs is accompanied by inhibition of AKT/mTOR, ERK and JAK2/STAT3 pathways, which supports its use to inhibit PCO in preclinical studies and provides theoretical foundation for future possible practice.

Targeted inhibition of mammalian target of rapamycin (mTOR) enhances radiosensitivity in pancreatic carcinoma cells

The mammalian target of rapamycin (mTOR) is a protein kinase that regulates protein translation, cell growth, and apoptosis. Rapamycin (RPM), a specific inhibitor of mTOR, exhibits potent and broad in vitro and in vivo antitumor activity against leukemia, breast cancer, and melanoma. Recent studies showing that RPM sensitizes cancers to chemotherapy and radiation therapy have attracted considerable attention. This study aimed to examine the radiosensitizing effect of RPM in vitro, as well as its mechanism of action. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and colony formation assay showed that 10 nmol/L to 15 nmol/L of RPM had a radiosensitizing effects on pancreatic carcinoma cells in vitro. Furthermore, a low dose of RPM induced autophagy and reduced the number of S-phase cells. When radiation treatment was combined with RPM, the PC-2 cell cycle arrested in the G2/M phase of the cell cycle. Complementary DNA (cDNA) microarray and reverse transcription polymerase chain reaction (RT-PCR) revealed that the expression of DDB1, RAD51, and XRCC5 were downregulated, whereas the expression of PCNA and ABCC4 were upregulated in PC-2 cells. The results demonstrated that RPM effectively enhanced the radiosensitivity of pancreatic carcinoma cells.

Antitumor effects of rapamycin in pancreatic cancer cells by inducing apoptosis and autophagy

Rapamycin (Rapa), an inhibitor of mammalian target of Rapamycin (mTOR), is an immunosuppressive agent that has anti-proliferative effects on some tumors. This study aims to investigate the effects of Rapa suppressing proliferation of pancreatic carcinoma PC-2 cells in vitro and its molecular mechanism involved in antitumor activities. MTT assays showed that the inhibition of proliferation of PC-2 cells in vitro was in a time- and dose-dependent manner. By using transmission electron microscopy, apoptosis bodies and formation of abundant autophagic vacuoles were observed in PC-2 cells after Rapa treatment. Flow cytometry assays also showed Rapa had a positive effect on apoptosis. MDC staining showed that the fluorescent density was higher and the number of MDC-labeled particles in PC-2 cells was greater in the Rapa treatment group than in the control group. RT-PCR revealed that the expression levels of p53, Bax and Beclin 1 were up-regulated in a dose-dependent manner, indicating that Beclin 1 was involved in Rapa induced autophagy and Rapa induced apoptosis as well as p53 up-regulation in PC-2 cells. The results demonstrated that Rapa could effectively inhibit proliferation and induce apoptosis and autophagy in PC-2 cells.

Prevention of β-amyloid degeneration of microglia by erythropoietin depends on Wnt1, the PI 3-K/mTOR pathway, Bad, and Bcl-xL

Central nervous system microglia promote neuronal regeneration and sequester toxic β-amyloid (Aβ) deposition during Alzheimer's disease. We show that the cytokine erythropoietin (EPO) decreases the toxic effect of Aβ on microgliain vitro. EPO up-regulates the cysteine-rich glycosylated wingless protein Wnt1 and activates the PI 3-K/Akt1/mTOR/ p70S6K pathway. This in turn increases phosphorylation and cytosol trafficking of Bad, reduces the Bad/Bcl-x_L complex and increases the Bcl-x_L/Bax complex, thus preventing caspase 1 and caspase 3 activation and apoptosis. Our data may foster development of novel strategies to use cytoprotectants such as EPO for Alzheimer's disease and other degenerative disorders.

Targeting serous epithelial ovarian cancer with designer zinc finger transcription factors

Ovarian cancer is the leading cause of death among gynecological malignancies. It is detected at late stages when the disease is spread through the abdominal cavity in a condition known as peritoneal carcinomatosis. Thus, there is an urgent need to develop novel therapeutic interventions to target advanced stages of ovarian cancer. Mammary serine protease inhibitor (Maspin) represents an important metastasis suppressor initially identified in breast cancer. Herein we have generated a sequence-specific zinc finger artificial transcription factor (ATF) to up-regulate the Maspin promoter in aggressive ovarian cancer cell lines and to interrogate the therapeutic potential of Maspin in ovarian cancer. We found that although Maspin was expressed in some primary ovarian tumors, the promoter was epigenetically silenced in cell lines derived from ascites. Transduction of the ATF in MOVCAR 5009 cells derived from ascitic cultures of a TgMISIIR-TAg mouse model of ovarian cancer resulted in tumor cell growth inhibition, impaired cell invasion, and severe disruption of actin cytoskeleton. Systemic delivery of lipid-protamine-RNA nanoparticles encapsulating a chemically modified ATF mRNA resulted in inhibition of ovarian cancer cell growth in nude mice accompanied with Maspin re-expression in the treated tumors. Gene expression microarrays of ATF-transduced cells revealed an exceptional specificity for the Maspin promoter. These analyses identified novel targets co-regulated with Maspin in human short-term cultures derived from ascites, such as TSPAN12, that could mediate the anti-metastatic phenotype of the ATF. Our work outlined the first targeted, non-viral delivery of ATFs into tumors with potential clinical applications for metastatic ovarian cancers.

Dietary energy balance modulates epithelial-to-mesenchymal transition and tumor progression in murine claudin-low and basal-like mammary tumor models

Using novel murine models of claudin-low and basal-like breast cancer, we tested the hypothesis that diet-induced obesity (DIO) and calorie restriction (CR) differentially modulate progression of these aggressive breast cancer subtypes. For model development, we characterized two cell lines, "mesenchymal (M)-Wnt" and "epithelial (E)-Wnt," derived from MMTV-Wnt-1 transgenic mouse mammary tumors. M-Wnt, relative to E-Wnt, cells were tumor-initiating cell (TIC)-enriched (62% vs. 2.4% CD44(high)/CD24(low)) and displayed enhanced ALDEFLUOR positivity, epithelial-to-mesenchymal transition (EMT) marker expression, mammosphere-forming ability, migration, invasion, and tumorigenicity (P < 0.001; each parameter). M-Wnt and E-Wnt cells clustered with claudin-low and basal-like breast tumors, respectively, in gene expression profiles and recapitulated these tumors when orthotopically transplanted into ovariectomized C57BL/6 mice. To assess the effects of energy balance interventions on tumor progression and EMT, mice were administered DIO, control, or CR diets for 8 weeks before orthotopic transplantation of M-Wnt or E-Wnt cells (for each cell line, n = 20 mice per diet) and continued on their diets for 6 weeks while tumor growth was monitored. Relative to control, DIO enhanced M-Wnt (P = 0.01), but not E-Wnt, tumor progression; upregulated EMT- and TIC-associated markers including N-cadherin,fibronectin, TGFβ, Snail, FOXC2, and Oct4 (P < 0.05, each); and increased intratumoral adipocytes. Conversely, CR suppressed M-Wnt and E-Wnt tumor progression (P < 0.02, each) and inhibited EMT and intratumoral adipocyte accumulation. Thus, dietary energy balance interventions differentially modulate EMT and progression of claudin-low and basal-like tumors. EMT pathway components may represent targets for breaking the obesity-breast cancer link, particularly for preventing and/or controlling TIC-enriched subtypes such as claudin-low breast cancer.

A systematic study of gene mutations in urothelial carcinoma; inactivating mutations in TSC2 and PIK3R1

Background

Urothelial carcinoma (UC) is characterized by frequent gene mutations of which activating mutations in FGFR3 are the most frequent. Several downstream targets of FGFR3 are also mutated in UC, e.g., PIK3CA, AKT1, and RAS. Most mutation studies of UCs have been focused on single or a few genes at the time or been performed on small sample series. This has limited the possibility to investigate co-occurrence of mutations.

Methodology/Principal Findings

We performed mutation analyses of 16 genes, FGFR3, PIK3CA, PIK3R1 PTEN, AKT1, KRAS, HRAS, NRAS, BRAF, ARAF, RAF1, TSC1, TSC2, APC, CTNNB1, and TP53, in 145 cases of UC. We show that FGFR3 and PIK3CA mutations are positively associated. In addition, we identified PIK3R1 as a target for mutations. We demonstrate a negative association at borderline significance between FGFR3 and RAS mutations, and show that these mutations are not strictly mutually exclusive. We show that mutations in BRAF, ARAF, RAF1 rarely occurs in UC. Our data emphasize the possible importance of APC signaling as 6% of the investigated tumors either showed inactivating APC or activating CTNNB1 mutations. TSC1, as well as TSC2, that constitute the mTOR regulatory tuberous sclerosis complex were found to be mutated at a combined frequency of 15%.

Conclusions/Significance

Our data demonstrate a significant association between FGFR3 and PIK3CA mutations in UC. Moreover, the identification of mutations in PIK3R1 further emphasizes the importance of the PI3-kinase pathway in UC. The presence of TSC2 mutations, in addition to TSC1 mutations, underlines the involvement of mTOR signaling in UC.

Molecular characterisation of side population cells with cancer stem cell-like characteristics in small-cell lung cancer

Background:

Side population (SP) fraction cells, identified by efflux of Hoechst dye, are present in virtually all normal and malignant tissues. The relationship between SP cells, drug resistance and cancer stem cells is poorly understood. Small-cell lung cancer (SCLC) is a highly aggressive human tumour with a 5-year survival rate of <10%. These features suggest enrichment in cancer stem cells.

Methods and results:

We examined several SCLC cell lines and found that they contain a consistent SP fraction that comprises <1% of the bulk population. Side population cells have higher proliferative capacity in vitro, efficient self-renewal and reduced cell surface expression of neuronal differentiation markers, CD56 and CD90, as compared with non-SP cells. Previous reports indicated that several thousand SP cells from non-small-cell lung cancer are required to form tumours in mice. In contrast, as few as 50 SP cells from H146 and H526 SCLC cell lines rapidly reconstituted tumours. Whereas non-SP cells formed fewer and slower-growing tumours, SP cells over-expressed many genes associated with cancer stem cell and drug resistance: ABCG2, FGF1, IGF1, MYC, SOX1/2, WNT1, as well as genes involved in angiogenesis, Notch and Hedgehog pathways.

Conclusions:

Side population cells from SCLC are highly enriched in tumourigenic cells and are characterised by a specific stem cell-associated gene expression signature. This gene signature may be used for development of targeted therapies for this rapidly fatal tumour.

Treating triple-negative breast cancer by a combination of rapamycin and cyclophosphamide: an in vivo bioluminescence imaging study

Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, has been shown to inhibit the growth of oestrogen positive breast cancer. However, triple-negative (TN) breast cancer is resistant to rapamycin treatment in vitro. We set to test a combination treatment of rapamycin with DNA-damage agent, cyclophosphamide, in a TN breast cancer model. By binding to and disrupting cellular DNA, cyclophosphamide kills cells via interfering with their normal functions. We assessed the responses of nude mice bearing tumour xenografts of TN MDA-MB-231 cells to the combination of rapamycin and cyclophosphamide in both orthotopic mammary and lung-metastasis models. We tracked tumour growth and metastasis by bioluminescent imaging and examined the expression of Ki67, CD34 and HIF-1alpha in tumour tissues by immunohistochemistry and apoptosis index with TUNEL assay, and found that MDA-MB-231 cells are sensitive to rapamycin therapy in orthotopic mammary, but not in lung with metastasis. Rapamycin when combined with cyclophosphamide is found to have a more significant effect in reducing tumour volume and metastasis with a much improved survival rate. Our data also show that the sensitivity of TN tumours to rapamycin is associated with the microenvironment of the tumour cells. The data indicate that in a relatively hypoxic environment HIF-1alpha may play a role in mediating the anti-cancer effect of rapamycin and cyclophosphamide may prevent the feedback activation of Akt by rapamycin. Overall our results show that rapamycin plus cyclophosphamide can achieve an improved efficacy in suppressing tumour growth and metastasis, suggesting that the combination therapy can be a promising treatment option for TN cancer.

Antitumor effects of ursolic acid in a mouse model of postmenopausal breast cancer

Over the past two decades, bioactive natural compounds have been shown to be a plausible adjunct to the treatment of breast cancer, the second leading cause of cancer death among American women. This study was designed to investigate the effects of ursolic acid (UA), a pentacyclic triterpene found in many foods and herbs, in a model of postmenopausal breast cancer. Ovariectomized C57BL/6 mice (n = 40) were randomized to receive control diet (AIN-93G) or diet supplemented with UA at 1 of 3 doses (wt/wt): 0.05%, 0.10%, or 0.25% (≈54, 106, or 266 mg/kg body weight/day, respectively). After 3 wk, syngeneic MMTV-Wnt-1 mammary tumor cells were injected in the mammary fat pad, and mice continued on their respective diets for 5 more wk. All UA doses decreased tumor cell proliferation, as assessed by Ki67 immunostaining; nevertheless, UA at 0.10% was most effective in inhibiting tumor take and decreasing tumor final tumor size. Modulation of Akt/mTOR signaling and induction of apoptosis appeared to mediate these effects on tumor growth. UA potently disrupted cell cycle progression and induced necrosis in a clonal MMTV-Wnt-1 mammary tumor cell line in vitro. This study supports the potential of UA as an antitumorigenic agent.