Autophagy suppresses Ras-driven epithelial tumourigenesis by limiting the accumulation of reactive oxygen species.

This corrects the article DOI: 10.1038/onc.2017.175.

Autophagy suppresses Ras-driven epithelial tumourigenesis by limiting the accumulation of reactive oxygen species.

Activation of Ras signalling occurs in ~30% of human cancers; however, activated Ras alone is not sufficient for tumourigenesis. In a screen for tumour suppressors that cooperate with oncogenic Ras (RasV12) in Drosophila, we identified genes involved in the autophagy pathway. Bioinformatic analysis of human tumours revealed that several core autophagy genes, including GABARAP, correlate with oncogenic KRAS mutations and poor prognosis in human pancreatic cancer, supporting a potential tumour-suppressive effect of the pathway in Ras-driven human cancers. In Drosophila, we demonstrate that blocking autophagy at any step of the pathway enhances RasV12-driven epithelial tissue overgrowth via the accumulation of reactive oxygen species and activation of the Jun kinase stress response pathway. Blocking autophagy in RasV12 clones also results in non-cell-autonomous effects with autophagy, cell proliferation and caspase activation induced in adjacent wild-type cells. Our study has implications for understanding the interplay between perturbations in Ras signalling and autophagy in tumourigenesis, which might inform the development of novel therapeutics targeting Ras-driven cancers.

Vorinostat in combination with lenalidomide and dexamethasone in patients with relapsed or refractory multiple myeloma.

The addition of vorinostat to lenalidomide/dexamethasone represents a novel combination therapy in multiple myeloma (MM), informed by laboratory studies suggesting synergy. This was a phase I, multicenter, open-label, non-randomized, dose-escalating study in patients with relapsed or relapsed and refractory MM. Clinical evaluation, electrocardiogram, laboratory studies and adverse events were obtained and assessed. The maximum-tolerated dose was not reached owing to a non-occurrence of two dose-limiting toxicities per six patients tested at any of the dosing levels. Patients tolerated the highest dose tested (Level 5) and this was considered the maximum administered dose: at 400 mg vorinostat on days 1-7 and 15-21, 25 mg lenalidomide on days 1-21 and 40 mg dexamethasone on days 1, 8, 15 and 22, per 28-day cycle. Drug-related adverse events were reported in 90% of patients serious adverse experiences were reported in 45% of the patients and 22% of all patients had adverse experiences considered, possibly related to study drug by the investigators. A confirmed partial response or better was reported for 14/30 patients (47%) evaluable for efficacy, including 31% of patients previously treated with lenalidomide. Vorinostat in combination with lenalidomide and dexamethasone proved tolerable with appropriate supportive care, with encouraging activity observed.

A novel rapid-onset high-penetrance plasmacytoma mouse model driven by deregulation of cMYC cooperating with KRAS12V in BALB/c mice.

Our goal is to develop a rapid and scalable system for functionally evaluating deregulated genes in multiple myeloma (MM). Here, we forcibly expressed human cMYC and KRAS12V in mouse T2 B cells (IgM(+)B220(+)CD38(+)IgD(+)) using retroviral transduction and transplanted these cells into lethally irradiated recipient mice. Recipients developed plasmacytomas with short onset (70 days) and high penetrance, whereas neither cMYC nor KRAS12V alone induced disease in recipient mice. Tumor cell morphology and cell surface biomarkers (CD138(+)B220(-)IgM(-)GFP(+)) indicate a plasma cell neoplasm. Gene set enrichment analysis further confirms that the tumor cells have a plasma cell gene expression signature. Plasmacytoma cells infiltrated multiple loci in the bone marrow, spleen and liver; secreted immunoglobulins; and caused glomerular damage. Our findings therefore demonstrate that deregulated expression of cMYC with KRAS12V in T2 B cells rapidly generates a plasma cell disease in mice, suggesting utility of this model both to elucidate molecular pathogenesis and to validate novel targeted therapies.

Using combination therapy to override stromal-mediated chemoresistance in mutant FLT3-positive AML: synergism between FLT3 inhibitors, dasatinib/multi-targeted inhibitors and JAK inhibitors.

Acute myeloid leukemia (AML) progenitors are frequently characterized by activating mutations in the receptor tyrosine kinase Fms-like tyrosine kinase-3 (FLT3). Protein tyrosine kinases are integral components of signaling cascades that have a role in both FLT3-mediated transformation as well as viability pathways that are advantageous to leukemic cell survival. The bone marrow microenvironment can diminish AML sensitivity to tyrosine kinase inhibitors. We hypothesized that inhibition of protein kinases in addition to FLT3 may be effective in overriding drug resistance in AML. We used a cell-based model mimicking stromal protection as part of an unbiased high-throughput chemical screen to identify kinase inhibitors with the potential to override microenvironment-mediated drug resistance in mutant FLT3-positive AML. Several related multi-targeted kinase inhibitors, including dasatinib, with the capability of reversing microenvironment-induced resistance to FLT3 inhibition were identified and validated. We validated synergy in vitro and demonstrated effective combination potential in vivo. In particular Janus kinase inhibitors were effective in overriding stromal protection and potentiating FLT3 inhibition in primary AML and cell lines. These results hint at a novel concept of using combination therapy to override drug resistance in mutant FLT3-positive AML in the bone marrow niche and suppress or eradicate residual disease.

The use of novel agents in the treatment of relapsed and refractory multiple myeloma.

Although outcomes for patients with multiple myeloma (MM) have improved over the past decade, the disease remains incurable and even patients who respond well to induction therapy ultimately relapse and require additional treatment. Conventional chemotherapy and high-dose therapy with stem cell transplantation (SCT) have historically been utilized in the management of relapsed MM, but in recent years the immunomodulatory drugs (IMiDs) thalidomide and lenalidomide, as well as the proteasome inhibitor bortezomib, have assumed a primary role in this setting. This review focuses on the role of thalidomide, lenalidomide and bortezomib in relapsed and refractory MM, with additional discussion dedicated to emerging drugs in relapsed MM that may prove beneficial to patients with this disease.

Preclinical activity of P276-00, a novel small-molecule cyclin-dependent kinase inhibitor in the therapy of multiple myeloma.

Cyclin D dysregulation and overexpression is noted in the majority of multiple myeloma (MM) patients, suggesting its critical role in MM pathogenesis. Here, we sought to identify the effects of targeting cyclin D in MM. We first confirmed cyclin D mRNA overexpression in 42 of 64 (65%) patient plasma cells. Silencing cyclin D1 resulted in >50% apoptotic cell death suggesting its validity as a potential therapeutic target. We next evaluated P276-00, a clinical-grade small-molecule cyclin-dependent kinase inhibitor as a way to target the cyclins. P276-00 resulted in dose-dependent cytotoxicity in MM cells. Cell-cycle analysis confirmed either growth arrest or caspase-dependent apoptosis; this was preceded by inhibition of Rb-1 phosphorylation with associated downregulation of a range of cyclins suggesting a regulatory role of P276-00 in cell-cycle progression through broad activity. Proliferative stimuli such as interleukin-6, insulin-like growth factor-1 and bone-marrow stromal cell adherence induced cyclins; P276-00 overcame these growth, survival and drug resistance signals. Because the cyclins are substrates of proteasome degradation, combination studies with bortezomib resulted in synergism. Finally, in vivo efficacy of P276-00 was confirmed in an MM xenograft model. These studies form the basis of an ongoing phase I study in the treatment of relapsed/refractory MM.

Lenalidomide inhibits osteoclastogenesis, survival factors and bone-remodeling markers in multiple myeloma.

Osteolytic bone disease in multiple myeloma (MM) is caused by enhanced osteoclast (OCL) activation and inhibition of osteoblast function. Lenalidomide and bortezomib have shown promising response rates in relapsed and newly diagnosed MM, and bortezomib has recently been reported to inhibit OCLs. We here investigated the effect of lenalidomide on OCL formation and osteoclastogenesis in comparison with bortezomib. Both drugs decreased alpha V beta 3-integrin, tartrate-resistant acid phosphatase-positive cells and bone resorption on dentin disks. In addition, both agents decreased receptor activator of nuclear factor-kappaB ligand (RANKL) secretion of bone marrow stromal cells (BMSCs) derived from MM patients. We identified PU.1 and pERK as major targets of lenalidomide, and nuclear factor of activated T cells of bortezomib, resulting in inhibition of osteoclastogenesis. Furthermore, downregulation of cathepsin K, essential for resorption of the bone collagen matrix, was observed. We demonstrated a significant decrease of growth and survival factors including macrophage inflammatory protein-alpha, B-cell activating factor and a proliferation-inducing ligand. Importantly, in serum from MM patients treated with lenalidomide, the essential bone-remodeling factor RANKL, as well as the RANKL/OPG ratio, were significantly reduced, whereas osteoprotegerin (OPG) was increased. We conclude that both agents specifically target key factors in osteoclastogenesis, and could directly affect the MM-OCL-BMSCs activation loop in osteolytic bone disease.

Telomerase inhibitor GRN163L inhibits myeloma cell growth in vitro and in vivo.

Human telomerase, the reverse transcriptase which extends the life span of a cell by adding telomeric repeats to chromosome ends, is expressed in most cancer cells but not in the majority of normal somatic cells. Inhibition of telomerase therefore holds great promise as anticancer therapy. We have synthesized a novel telomerase inhibitor GRN163L, a lipid-attached phosphoramidate oligonucleotide complementary to template region of the RNA subunit of telomerase. Here, we report that GRN163L is efficiently taken up by human myeloma cells without any need of transfection and is resistant to nucleolytic degradation. The exposure of myeloma cells to GRN163L led to an effective inhibition of telomerase activity, reduction of telomere length and apoptotic cell death after a lag period of 2-3 weeks. Mismatch control oligonucleotides had no effect on growth of myeloma cells. The in vivo efficacy of GRN163L was confirmed in two murine models of human multiple myeloma. In three independent experiments, significant reduction in tumor cell growth and better survival than control mice was observed. Furthermore, GRN163L-induced myeloma cell death could be significantly enhanced by Hsp90 inhibitor 17AAG. These data provide the preclinical rationale for clinical evaluation of GRN163L in myeloma and in combination with 17AAG.

2-Methoxyestardiol and bortezomib/proteasome-inhibitor overcome dexamethasone-resistance in multiple myeloma cells by modulating Heat Shock Protein-27.

Multiple myeloma (MM) remains fatal despite all available therapies. Initial treatment with conventional drugs such as, Dexamethasone (Dex) effectively induces MM cell death; however, prolonged drug exposures results in the development of chemoresistance. Our prior study demonstrated that 2-Methoxyestradiol (2ME2) induces apoptosis in multiple myeloma (MM) cells resistant to Dexamethasone (Dex). Here, we show the mechanism whereby 2ME2 overcomes Dex-resistance. The oligonucleotide array analysis demonstrates that Heat Shock Protein-27 (Hsp27) is upregulated in Dex-resistant, but not in Dex-sensitive MM cells. Proteomics analysis of Hsp27-immunocomplexes revealed the presence of actin in Dex-resistant, but not in Dex-sensitive cells. Biochemical interaction between Hsp27 and actin was examined by co-immunoprecipitation with anti-Hsp27 or actin Abs. Far western blot analysis using GST-Hsp27 fusion protein showed a direct association with actin both in vitro and in vivo. Importantly, 2ME2- or Bortezomib/Proteasome inhibitor (PS-341)-induced apoptosis in Dex-resistant MM cell lines and MM patient cells is associated with disruption of the Hsp27-actin complexes. Finally, blockade of Hsp27 by anti-sense strategy enhanced anti-MM activity of both 2ME2 and PS-341. These findings provide the clinical application of novel therapeutics targeting Hsp27 to improve patient outcome in MM.

The role of apoptosis-inducing receptors of the tumor necrosis factor family in thyroid cancer.

The tumor necrosis factor (TNF) family comprises several ligands, such as the prototype TNF-alpha, the Fas ligand (FasL) and TNF-related apoptosis-inducing ligand (TRAIL/Apo2L), which trigger apoptosis in susceptible cells by activating respective cell-surface receptors. The study of these cell death pathways has attracted significant attention in several fields, including that of thyroid cancer, because they participate in immune system function, as an arm of cell-mediated cytotoxicity, and because recombinant ligands are available for pharmacological use. TNF-alpha is a pluripotent cytokine that induces both pro-apoptotic and anti-apoptotic effects on thyroid carcinoma cells. FasL triggers apoptosis in other tumor types, but thyroid carcinoma cells are resistant to this effect. On the other hand, TRAIL potently and selectively kills thyroid carcinoma cells. Consequently, TRAIL is the only member of the family with significant anticancer activity and an acceptable toxicity profile to be used as a novel therapy for thyroid cancer. The caspase inhibitor FLIP plays a significant role in negatively regulating receptor-induced apoptosis. Thelper 1-type cytokines, such as interferon-gamma, TNF-alpha and interleukin-1beta increase the sensitivity of both normal and neoplastic thyrocytes to FasL and TRAIL. On the other hand, IGF-I and other growth/survival factors produced in the local tumor microenvironment activate the phosphatidylinositol 3-kinase/Akt kinase pathway and exert an anti-apoptotic effect by upregulating several apoptosis inhibitors, including FLIP. Pharmacological modulation of apoptosis induced by FasL and TRAIL/Apo2L holds promise of therapeutic applications in human malignancies.

Endocrine/paracrine/autocrine survival factor activity of bone microenvironment participates in the development of androgen ablation and chemotherapy refractoriness of prostate cancer metastasis in skeleton.

Bone is the most frequent site of metastases of prostate cancer and is almost always the first and frequently the only site of metastases where disease will progress to stage D3. In addition, the number of skeletal metastatic foci is the most powerful independent prognostic factor of limited response to hormone ablation therapy and poor survival of patients with advanced prostate cancer. Furthermore, disease progression frequently occurs in the osteoblastic metastases, even though androgen ablation therapy still provides adequate and sustained control of disease at the primary site. Notably, the management of metastatic disease onto bones has traditionally relied on therapeutic modalities, which almost exclusively aim at directly inducing cancer cell death. However, accumulating pieces of evidence, from both the clinical and the basic research front, point to major limitations of this conventional approach. The in vivo response of malignant cells to anticancer therapies is directly influenced by the local microenvironment in which they metastasize. In particular, organ sites frequently involved in metastatic diseases, such as the bones, appear to confer to metastatic cells protection from anticancer drug-induced apoptosis. This protection is mediated by soluble growth factors and cytokines released by the normal cellular constituents of the host tissue microenvironment. The characterization of bone microenvironment-related survival factors has led to the development of a novel hormone manipulation which can re-introduce clinical responses in patients with stage D3 prostate cancer.

A combination therapy of dexamethasone and somatostatin analog reintroduces objective clinical responses to LHRH analog in androgen ablation-refractory prostate cancer patients.

We evaluated whether the combination of triptorelin, a LHRH analog (LHRH-A), with dexamethasone and lanreotide, a somatostatin analog, can produce objective clinical responses in metastatic androgen ablation-refractory prostate cancer (stage D3) patients who have relapsed, after combined androgen blockade (LHRH-A plus antiandrogen) and antiandrogen withdrawal. Eleven stage D3 patients with diffuse bony metastases, who had progressed despite initial responses (lasting <12 months) to combined androgen blockade therapy and subsequently failed antiandrogen withdrawal, received oral dexamethasone (4 mg daily for the first month, tapered down to 2 mg after the first month and 1 mg after the second month, and continued on 1 mg thereafter) and lanreotide (30 mg im every 14 d) in combination with triptorelin (3.75 mg im every 28 d). Serum prostate-specific antigen, alkaline phosphatase, performance status, and bone pain were assessed monthly during therapy. Fasting blood glucose was measured biweekly, and serum IGF-I, T, and dehydroepiandrosterone sulfate levels were assessed at baseline, at response to the combination therapy, and at relapse from it. Ten of 11 stage D3 patients [90.9% of patients; 95% confidence interval (CI), 58.7-99.8%] had durable objective clinical responses (including > or = 50% prostate-specific antigen decline in 8 patients, 72.7%; 95% CI, 39-94%). All patients reported significant and durable improvement of bone pain (for a median duration of 13 months; 95% CI, 12-14 months; range, 6-22 months) and performance status (median duration, 19 months; 95% CI, 13-25 months; range, 7-22 months) without major treatment-related side effects. The median progression-free survival was 7 months (95% CI, 4-10 months; range, 3-17 months), and the median overall survival was 18 months (95% CI, 16-20 months; range, 7-22 months). Five of six total deaths occurred secondary to disease progression. We observed a statistically significant (P = 0.018) reduction in serum IGF-I levels at response to the combination therapy (60% reduction of baseline IGF-I levels). Dehydroepiandrosterone sulfate levels, although already significantly suppressed at baseline, had an additional significant reduction (P < 0.02) at response to therapy. T levels remained suppressed within castration levels (<3 nmol/liter, at baseline and throughout therapy, including relapse). The combination therapy of LHRH-A with dexamethasone plus somatostatin analog produces objective clinical responses and symptomatic improvement in androgen ablation (LHRH-A) refractory prostate cancer patients.

Apoptosis induced by FasL and TRAIL/Apo2L in the pathogenesis of thyroid diseases.

FasL and TRAIL/Apo2L participate in cell-mediated cytotoxicity by inducing apoptosis in susceptible cells via respective cell surface receptors. Normal and neoplastic thyroid tissues are resistant to FasL-induced apoptosis but are sensitized by Th-1-type cytokines. In Hashimoto's thyroiditis, both FasL and its receptor, Fas, are strongly upregulated and their interaction leads to the suicidal/fratricidal death of thyrocytes. In Graves' disease, FasL expression in thyroid follicular cells is induced by thionamides and kills infiltrating lymphocytes. In this condition, Th-2-type cytokines upregulate the anti-apoptotic molecules FLIP and Bcl-x(L) and protect thyrocytes from apoptosis. FasL is expressed by neoplastic thyrocytes and induces apoptosis of infiltrating lymphocytes. TRAIL/Apo2L kills thyroid carcinoma cells but spares normal thyrocytes, thus providing a potential therapy for thyroid cancer.

Vascular endothelial growth factor triggers signaling cascades mediating multiple myeloma cell growth and migration.

Multiple myeloma (MM) remains incurable, with a median survival of 3 to 4 years. This study shows direct effects of vascular endothelial growth factor (VEGF) upon MM and plasma cell leukemia (PCL) cells. The results indicate that VEGF triggers tumor cell proliferation via a protein kinase C (PKC)-independent Raf-1-MEK-extracellular signal-regulated protein kinase pathway, and migration via a PKC-dependent pathway. These observations provide the framework for novel therapeutic strategies targeting VEGF signaling cascades in MM.

TRAIL/Apo2L ligand selectively induces apoptosis and overcomes drug resistance in multiple myeloma: therapeutic applications.

Multiple myeloma (MM) remains incurable and novel treatments are urgently needed. Preclinical in vitro and in vivo evaluations were performed to assess the potential therapeutic applications of human recombinant tumor necrosis factor (TNF)-related apoptosis-inducing ligand/Apo2 ligand (TRAIL/Apo2L) in MM. TRAIL/Apo2L potently induced apoptosis of MM cells from patients and the majority of MM cell lines, including cells sensitive or resistant to dexamethasone (Dex), doxorubicin (Dox), melphalan, and mitoxantrone. TRAIL/Apo2L also overcame the survival effect of interleukin 6 on MM cells and did not affect the survival of peripheral blood and bone marrow mononuclear cells and purified B cells from healthy donors. The status of the TRAIL receptors (assessed by immunoblotting and flow cytometry) could not predict TRAIL sensitivity of MM cells. The anti-MM activity of TRAIL/Apo2L was confirmed in nu/xid/bg mice xenografted with human MM cells; TRAIL (500 microg intraperitoneally daily for 14 days) was well tolerated and significantly suppressed the growth of plasmacytomas. Dox up-regulated the expression of the TRAIL receptor death receptor 5 (DR5) and synergistically enhanced the effect of TRAIL not only against MM cells sensitive to, but also against those resistant to, Dex- or Dox-induced apoptosis. Nuclear factor (NF)-kappaB inhibitors, such as SN50 (a cell-permeable inhibitor of the nuclear translocation and transcriptional activity of NF-kappaB) or the proteasome inhibitor PS-341, enhanced the proapoptotic activity of TRAIL/Apo2L against TRAIL-sensitive MM cells, whereas SN50 reversed the TRAIL resistance of ARH-77 and IM-9 MM cells. Importantly, normal B lymphocytes were not sensitized to TRAIL by either Dox, SN50, or PS-341. These preclinical studies suggest that TRAIL/Apo2L can overcome conventional drug resistance and provide the basis for clinical trials of TRAIL-based treatment regimens to improve outcome in patients with MM. (Blood. 2001;98:795-804)

Tumor cell expression of CD59 is associated with resistance to CD20 serotherapy in patients with B-cell malignancies.

The anti-CD20 chimeric monoclonal antibody rituximab (Rituxan) is used to treat patients with various B-cell tumors, including patients with plasma cell dyscrasias who have CD20+ disease. Many patients with CD20+ disease have either primary unresponsive disease or progress after initially responding to rituximab; therefore, understanding how tumor cells are, or become, resistant to rituximab is of clinical relevance. In this report, we determined whether tumor cells express antigens that block complement-mediated lysis or antibody-dependent cell-mediated cytotoxicity (ADCC) and thereby contribute to rituximab resistance. We demonstrate that expression of the complement regulator CD59 is associated with resistance to rituximab-mediated complement lysis of multiple myeloma (MM) and non-Hodgkin's lymphoma (NHL) cell lines. Moreover, neutralization of CD59 using a blocking monoclonal antibody reversed resistance to rituximab-mediated complement lysis of CD20++ CD59++ ARH-77 MM cells. In addition, we demonstrate the presence of CD59 and rituximab binding on viable tumor cells from patients with MM and Waldenstrom's macroglobulinemia with progressive disease despite rituximab therapy. Last, we also examined MM and NHL B-cell lines, as well as patient tumor cells, for the expression of other antigens that may have a role in blocking ADCC activity, such as Fas ligand (FasL), MUCI, or TRAIL. FasL, MUC1, and/or TRAIL were coexpressed with complement regulators on many of these cells. These studies therefore show that complement regulators, particularly CD59 and antigens that may block ADCC, are present on various B-cell tumors and associated with rituximab resistance in patients. A prospective, clinical study is assessing the role of these antigens in mediating rituximab resistance.

Ewing's sarcoma family tumors are sensitive to tumor necrosis factor-related apoptosis-inducing ligand and express death receptor 4 and death receptor 5.

In this study, we investigated the sensitivity of Ewing's sarcoma family tumors (ESFTs) of children and adolescents to the tumor necrosis factor-related apoptosis-inducing Ligand (TRAIL). TRAIL binds to death receptors (DRs) DR4, DR5, DcR1, and DcR2. Either DR4 or DR5 can induce apoptosis, whereas DcR1 and DcR2 are considered inhibitory receptors. Nine of 10 ESFT cell lines, including several that were Fas resistant, underwent apoptosis with TRAIL through activation of caspase-10, capase-8 (FLICE), caspase-3, and caspase-9. In contrast to the Fas signaling pathway, caspase-10, but not caspase-8 or the Fas-associated death domain-containing molecule, was recruited to the TRAIL receptor-associated signaling complex. We found that 9 of 10 ESFT cell lines expressed both DR4 and DR5 by Western blotting, whereas the TRAIL-resistant line expressed only DR4. However, DR4 was absent from the cell surface in the resistant and two additional lines (three of five tested lines), suggesting that it may have been nonfunctional. On the contrary, DR5 was located on the cell surface in all four sensitive lines tested, being absent only from the cell surface of the resistant line that was also DR5-negative by Western blotting. In agreement with these findings, the resistance of the line was overcome by restoration of DR5 levels by transfection. Levels of DcR1 and DcR2 or levels of the FLICE-inhibitory protein (FLIP) did not correlate with TRAIL resistance, and protein synthesis inhibition did not sensitize the TRAIL-resistant line to TRAIL. Because these data suggested that sensitivity of ESFTs to TRAIL was mainly based on the presence of DR4/DR5, we investigated the presence of these receptors in 32 ESFT tissue sections by immunohistochemistry. We found that 23 of 32 tumor tissues (72%) expressed both receptors, 8 of 32 (25%) expressed one receptor only, and 1 was negative for both. Our finding of wide expression of DR4/DR5 in ESFT in vivo, in combination with their high sensitivity to TRAIL in vitro and the reported lack of toxicity of TRAIL in mice and monkeys, suggests that TRAIL may be a novel effective agent in the treatment of ESFTs.