Immune Pharmacodynamic Responses of the Novel Cancer Immunotherapeutic Imprime PGG in Healthy Volunteers.

Imprime PGG (Imprime) is an i.v. administered, yeast ß-1,3/1,6 glucan in clinical development with checkpoint inhibitors. Imprime-mediated innate immune activation requires immune complex formation with naturally occurring IgG anti-ß glucan Abs (ABA). We administered Imprime to healthy human volunteers to assess the necessity of ABA for Imprime-mediated immunopharmacodynamic (IPD) changes. Imprime (4 mg/kg) was administered i.v. in single and multiple infusions. Subsets of subjects were premedicated with antihistamine and corticosteroid. Peripheral blood was measured before, during and after Imprime administration for IPD changes (e.g., ABA, circulating immune complexes, complement activation, complete blood counts, cytokine/chemokine, and gene expression changes). IPD changes were analyzed based on pretreatment serum ABA levels: low-ABA (<20 µg/ml), mid-ABA (≥20-50 µg/ml), and high-ABA (≥50 µg/ml). At the end of infusion, free serum ABA levels decreased, circulating immune complex levels increased, and complement activation was observed. At ∼1-4 h after end of infusion, increased expression of cytokines/chemokines, a 1.5-4-fold increase in neutrophil and monocyte counts and a broad activation of innate immune genes were observed. Low-ABA subjects typically showed minimal IPD changes except when ABA levels rose above 20 µg/ml after repeated Imprime dosing. Mild-to-moderate infusion-related reactions occurred in subjects with ABA ≥20 µg/ml. Premedications alleviated some of the infusion-related reactions, but also inhibited cytokine responses. In conclusion, ABA levels, being critical for Imprime-mediated immune activation may provide a plausible, mechanism-based biomarker to identify patients most likely to respond to Imprime-based anticancer immunotherapy.

Phosphorylation of eIF4E serine 209 is associated with tumour progression and reduced survival in malignant melanoma.

BACKGROUND: Melanoma is a disease that primarily arises in the skin but is a derivative of the neural crest. Eukaryotic translation initiation factor 4E (eIF4E) regulates translation of multiple malignancy-associated mRNAs and is overexpressed in many epithelial tumours. However, expression in human tumours derived from the neural crest is unknown. Here, we determined the association of eIF4E and phospho-eIF4E expression in melanocytic lesions with malignant conversion, metastatic potential and patient survival. METHODS: Archived formalin-fixed, paraffin-embedded surgical specimens from 114 patients with melanocytic lesions were stained immunohistochemically for eIF4E and phospho-eIF4E and evaluated semiquantitatively. The relationship between cytoplasmic and nuclear eIF4E and phospho-eIF4E protein expression, melanocytic lesion subtype and tumour progression was determined. Kaplan-Meier survival analyses and Cox proportional hazard regression were performed. RESULTS: Increased eIF4E and phospho-eIF4E expression was highly associated with malignancy (P<0.0001). High nuclear phospho-eIF4E was associated with synchronous or future metastasis (P=0.0059). Kaplan-Meier analyses demonstrated highly significant associations between high histoscores for cytoplasmic and nuclear phospho-eIF4E and reduced survival in all patients (P=0.0003 and 0.0009, respectively). CONCLUSIONS: Increased melanoma expression of eIF4E and phospho-eIF4E is associated with metastatic potential, reduced survival and increased risk of death.

Inhibition of Mnk kinase activity by cercosporamide and suppressive effects on acute myeloid leukemia precursors.

Mnk kinases regulate the phosphorylation and activation of the eukaryotic initiation factor 4E (eIF4E), a protein that plays key roles in the initiation of messenger RNA translation and whose activity is critical for various cellular functions. eIF4E is deregulated in acute myeloid leukemia (AML), and its aberrant activity contributes to leukemogenesis. We determined whether cercosporamide, an antifungal agent that was recently shown to act as a unique Mnk inhibitor, exhibits antileukemic properties. Treatment of AML cells with cercosporamide resulted in a dose-dependent suppression of eIF4E phosphorylation. Such suppression of Mnk kinase activity and eIF4E phosphorylation by cercosporamide resulted in dose-dependent suppressive effects on primitive leukemic progenitors (CFU-L) from AML patients and enhanced the antileukemic properties of cytarabine (Ara-C) or mammalian target of rapamycin (mTOR) complex 1 inhibition. Similarly, the combination of cercosporamide with cytarabine resulted in enhanced antileukemic responses in a xenograft mouse model in vivo. Altogether, this work demonstrates that the unique Mnk inhibitor cercosporamide suppresses phosphorylation of eIF4E and exhibits antileukemic effects, in support of future clinical-translational efforts involving combinations of Mnk inhibitors with cytarabine and/or mTOR inhibitors for the treatment of AML.

LY2801653 is an orally bioavailable multi-kinase inhibitor with potent activity against MET, MST1R, and other oncoproteins, and displays anti-tumor activities in mouse xenograft models.

The HGF/MET signaling pathway regulates a wide variety of normal cellular functions that can be subverted to support neoplasia, including cell proliferation, survival, apoptosis, scattering and motility, invasion, and angiogenesis. MET over-expression (with or without gene amplification), aberrant autocrine or paracrine ligand production, and missense MET mutations are mechanisms that lead to activation of the MET pathway in tumors and are associated with poor prognostic outcome. We report here preclinical development of a potent, orally bioavailable, small-molecule inhibitor LY2801653 targeting MET kinase. LY2801653 is a type-II ATP competitive, slow-off inhibitor of MET tyrosine kinase with a dissociation constant (Ki) of 2 nM, a pharmacodynamic residence time (Koff) of 0.00132 min(-1) and t1/2 of 525 min. LY2801653 demonstrated in vitro effects on MET pathway-dependent cell scattering and cell proliferation; in vivo anti-tumor effects in MET amplified (MKN45), MET autocrine (U-87MG, and KP4) and MET over-expressed (H441) xenograft models; and in vivo vessel normalization effects. LY2801653 also maintained potency against 13 MET variants, each bearing a single-point mutation. In subsequent nonclinical characterization, LY2801653 was found to have potent activity against several other receptor tyrosine oncokinases including MST1R, FLT3, AXL, MERTK, TEK, ROS1, DDR1/2 and against the serine/threonine kinases MKNK1/2. The potential value of MET and other inhibited targets within a number of malignancies (such as colon, bile ducts, and lung) is discussed. LY2801653 is currently in phase 1 clinical testing in patients with advanced cancer (trial I3O-MC-JSBA, NCT01285037).

Imprime PGG Enhances Anti-Tumor Effects of Tumor-Targeting, Anti-Angiogenic, and Immune Checkpoint Inhibitor Antibodies.

Imprime PGG (Imprime) is in late-stage clinical development as a combinatorial agent with several therapeutic modalities. Here we present pre-clinical mechanistic data supportive of Imprime, a soluble yeast ß-1,3/1,6-glucan pathogen-associated molecular pattern able to prime innate immune cells in a Dectin-1dependent manner. In tumor-free mice, Imprime evoked broad innate immune responses (type I interferon signature, mobilization of myeloid cells, dendritic cell and monocyte/macrophage expression of co-stimulatory ligands like CD86, and activation of natural killer cells). Imprime-mediated activation of myeloid cells also resulted in functional priming of antigen-specific CD8 T cell response. In tumor-bearing mice, Imprime monotherapy further resulted in activation of systemic and tumor infiltrating macrophages and enhanced cytotoxic CD8 T cell trafficking. Imprime enhanced the anti-tumor activity of several combinatorial agents in mouse cancer models; anti-tyrosinase-related protein 1 antibody in B16F10 melanoma experimental lung metastasis model, anti-vascular endothelial growth factor receptor 2 antibody in H1299 and H441 lung cancer, and anti-programmed cell death protein 1 antibody in MC38 colon cancer models. Mechanistically, combining Imprime with these combinatorial therapeutic agents elicited enhanced innate immune activation, supporting immunological synergy. Finally, Imprime treatment induced similar in vitro phenotypic and functional activation of human innate immune cells. Collectively, these data demonstrate Imprime's potential to orchestrate a broad, yet coordinated, anti-cancer immune response and complement existing cancer immunotherapies.

Therapeutic suppression of translation initiation factor eIF4E expression reduces tumor growth without toxicity.

Expression of eukaryotic translation initiation factor 4E (eIF4E) is commonly elevated in human and experimental cancers, promoting angiogenesis and tumor growth. Elevated eIF4E levels selectively increase translation of growth factors important in malignancy (e.g., VEGF, cyclin D1) and is thereby an attractive anticancer therapeutic target. Yet to date, no eIF4E-specific therapy has been developed. Herein we report development of eIF4E-specific antisense oligonucleotides (ASOs) designed to have the necessary tissue stability and nuclease resistance required for systemic anticancer therapy. In mammalian cultured cells, these ASOs specifically targeted the eIF4E mRNA for destruction, repressing expression of eIF4E-regulated proteins (e.g., VEGF, cyclin D1, survivin, c-myc, Bcl-2), inducing apoptosis, and preventing endothelial cells from forming vessel-like structures. Most importantly, intravenous ASO administration selectively and significantly reduced eIF4E expression in human tumor xenografts, significantly suppressing tumor growth. Because these ASOs also target murine eIF4E, we assessed the impact of eIF4E reduction in normal tissues. Despite reducing eIF4E levels by 80% in mouse liver, eIF4E-specific ASO administration did not affect body weight, organ weight, or liver transaminase levels, thereby providing the first in vivo evidence that cancers may be more susceptible to eIF4E inhibition than normal tissues. These data have prompted eIF4E-specific ASO clinical trials for the treatment of human cancers.

Preclinical assessment of galunisertib (LY2157299 monohydrate), a first-in-class transforming growth factor-ß receptor type I inhibitor.

Transforming growth factor-ß (TGFß) is an important driver of tumor growth via intrinsic and extrinsic mechanisms, and is therefore an attractive target for developing cancer therapeutics. Using preclinical models, we characterized the anti-tumor activity of a small molecule inhibitor of TGFß receptor I (TGFßRI), galunisertib (LY2157299 monohydrate). Galunisertib demonstrated potent and selective inhibition of TGFßRI with corresponding inhibition of downstream signaling via inhibition of SMAD phosphorylation (pSMAD). Galunisertib also inhibited TGFß-induced pSMAD in vivo, which enabled a pharmacokinetic/pharmacodynamic profile in Calu6 and EMT6-LM2 tumors. Galunisertib demonstrated anti-tumor activity including inhibition of tumor cell migration and mesenchymal phenotype, reversal of TGFß-mediated immune-suppression, and tumor growth delay. A concentration-effect relationship was established with a dosing schedule to achieve the optimal level of target modulation. Finally, a rat model demonstrated a correlation between galunisertib-dependent inhibition of pSMAD in tumor tissues and in PBMCs, supporting the use of PBMCs for assessing pharmacodynamic effects. Galunisertib has been tested in several clinical studies with evidence of anti-tumor activity observed in subsets of patients. Here, we demonstrate that galunisertib inhibits a number of TGFß-dependent functions leading to anti-tumor activity. The enhanced understanding of galunisertib provides rationale for further informed clinical development of TGFß pathway inhibitors.

Int7G24A variant of transforming growth factor-beta receptor type I is associated with invasive breast cancer.

PURPOSE: The transforming growth factor-beta (TGF-beta) signaling pathway has been frequently implicated in breast cancer. An intronic variant (Int7G24A) of TGF-beta receptor type I (TGFBR1) is associated with kidney and bladder cancers in our recent study. We hypothesize that this germline variant may be involved in development and progression of breast cancer. EXPERIMENTAL DESIGN: Case-control studies were designed from archived paraffin-embedded tissue specimens from the same geographic area with a homogenous ethnic population. We analyzed 223 patients (25 with preinvasive tumors and 198 with invasive and metastatic breast cancers) and 153 noncancer controls. The Int7G24A was identified by PCR-RFLP. Another germline deletion (TGFBR1*6A) and somatic mutations in the TGFBR1 were also analyzed by PCR and single-strand conformational polymorphism. RESULTS: The Int7G24A allele was evident in 32% of patients with preinvasive neoplasms and 48% of patients with invasive breast cancers compared with 26% controls (P = 0.00008). In addition, 11 (5.6%) homozygous Int7G24A carriers were found in patients with invasive breast cancers, whereas only 3 (2%) homozygous carriers were found in the control group. The TGFBR1*6A allele was not significantly associated with breast cancer patients and only one somatic mutation was found in 71 breast cancers. CONCLUSION: These data suggest that the germline Int7G24A variant may represent a risk factor for invasive breast cancer and a marker for breast cancer progression. A separate study with a larger sample size is warranted to validate the association of the Int7G24A with human breast cancer.

The protein kinase Cbeta-selective inhibitor, Enzastaurin (LY317615.HCl), suppresses signaling through the AKT pathway, induces apoptosis, and suppresses growth of human colon cancer and glioblastoma xenografts.

Activation of protein kinase Cbeta (PKCbeta) has been repeatedly implicated in tumor-induced angiogenesis. The PKCbeta-selective inhibitor, Enzastaurin (LY317615.HCl), suppresses angiogenesis and was advanced for clinical development based upon this antiangiogenic activity. Activation of PKCbeta has now also been implicated in tumor cell proliferation, apoptosis, and tumor invasiveness. Herein, we show that Enzastaurin has a direct effect on human tumor cells, inducing apoptosis and suppressing the proliferation of cultured tumor cells. Enzastaurin treatment also suppresses the phosphorylation of GSK3betaser9, ribosomal protein S6(S240/244), and AKT(Thr308). Oral dosing with Enzastaurin to yield plasma concentrations similar to those achieved in clinical trials significantly suppresses the growth of human glioblastoma and colon carcinoma xenografts. As in cultured tumor cells, Enzastaurin treatment suppresses the phosphorylation of GSK3beta in these xenograft tumor tissues. Enzastaurin treatment also suppresses GSK3beta phosphorylation to a similar extent in peripheral blood mononuclear cells (PBMCs) from these treated mice. These data show that Enzastaurin has a direct antitumor effect and that Enzastaurin treatment suppresses GSK3beta phosphorylation in both tumor tissue and in PBMCs, suggesting that GSK3beta phosphorylation may serve as a reliable pharmacodynamic marker for Enzastaurin activity. With previously published reports, these data support the notion that Enzastaurin suppresses tumor growth through multiple mechanisms: direct suppression of tumor cell proliferation and the induction of tumor cell death coupled to the indirect effect of suppressing tumor-induced angiogenesis.

The progression of LNCaP human prostate cancer cells to androgen independence involves decreased FOXO3a expression and reduced p27KIP1 promoter transactivation.

The progression of human prostate cancer from the initial androgen-dependent phase to androgen independence involves diminished apoptosis and a release from the cell cycle block triggered by androgen ablation therapy. FOXO transcription factors play a central role in promoting expression of proapoptotic and cell cycle regulatory genes (e.g., FasL and p27KIP1). Reduced FOXO function might, therefore, play a role in androgen-independent progression of human prostate cancer. Herein, we show that FOXO function is compromised in androgen-independent prostate cancer cells (LNAI) versus androgen-dependent LNCaP cells. The FOXO3a protein, the most highly expressed FOXO family member in prostate cancer cells, is hyperphosphorylated in LNAI cells. FOXO3a expression is also markedly reduced in these androgen-independent LNAI cells when compared with parental LNCaP cells. Together, reduced FOXO3a expression coupled to FOXO3a hyperphosphorylation would suppress FOXO transcriptional activity. Accordingly, activity of the FOXO-responsive p27KIP1 promoter is reduced 60% in these LNAI cells when compared with LNCaP cells. Moreover, mutation of a conserved FOXO response element suppresses p27KIP1 promoter activity, substantiating a regulatory role for this FOXO response element in p27KIP1 promoter transactivation. Finally, we show that the activity of a distinct FOXO-responsive promoter, the 3X-IRS promoter, is also reduced in LNAI cells. Collectively, these data show that reduced FOXO3a expression coupled to increased FOXO3a phosphorylation coincide with reduced FOXO-responsive promoter activity in androgen-independent LNAI cells when compared with androgen-dependent LNCaP cells. To the extent that this model reflects human disease, these data suggest that FOXO function may be compromised with androgen-independent progression of human prostate cancer.

The selective estrogen receptor modulator trioxifene (LY133314) inhibits metastasis and extends survival in the PAIII rat prostatic carcinoma model.

Trioxifene (LY133314) is a selective estrogen receptor modulator (SERM) with competitive binding activity against estradiol for estrogen receptor alpha (ERalpha) and antagonistic activity against ERalpha-mediated gene expression. The PAIII rat prostatic adenocarcinoma (PCa) is an androgen receptor-negative, ERalpha- and ERbeta-positive, spontaneously metastatic rodent tumor cell line. After s.c. implantation of 10(6) PAIII cells in the tail, s.c. administration of trioxifene (2.0, 4.0, 20.0, or 40.0 mg/kg-day) for 30 days produced significant (P < 0.05) inhibition of PAIII metastasis from the primary tumor in the tail to the gluteal and iliac lymph nodes (maximum nodal weight decreases, 86% and 88% from control values, respectively). PAIII metastasis to the lungs was significantly inhibited by trioxifene treatment. Numbers of pulmonary foci in PAIII-bearing rats were significantly (P < 0.05) reduced by trioxifene administration in a dose-related manner (maximal reduction, 98% from control values). Continual administration of the compound significantly (P < 0.05) extended survival of PAIII-bearing rats. Trioxifene inhibited the proliferation of PAIII cells at micromolar levels in vitro but did not slow growth of the primary tumor growth in the tail. Trioxifene administration also produced regression of male accessory sex organs. In PAIII-tumor-bearing animals, trioxifene administration produced a maximal regression of 76% for ventral prostate and 64% for seminal vesicle (P < 0.05 for both). SERMs may be preferable to estrogens given their efficacy in experimental PCa models and relative lack of side effects observed in clinical trials. Our data support the contention that trioxifene represents a SERM with potential antimetastatic efficacy for the treatment of androgen-independent, metastatic PCa.

Cotargeting MNK and MEK kinases induces the regression of NF1-mutant cancers.

Neurofibromin 1-mutant (NF1-mutant) cancers are driven by excessive Ras signaling; however, there are currently no effective therapies for these or other Ras-dependent tumors. While combined MEK and mTORC1 suppression causes regression of NF1-deficient malignancies in animal models, the potential toxicity of cotargeting these 2 major signaling pathways in humans may necessitate the identification of more refined, cancer-specific signaling nodes. Here, we have provided evidence that MAPK-interacting kinases (MNKs), which converge on the mTORC1 effector eIF4E, are therapeutic targets in NF1-deficient malignancies. Specifically, we evaluated primary human NF1-deficient peripheral nervous system tumors and found that MNKs are activated in the majority of tumors tested. Genetic and chemical suppression of MNKs in NF1-deficient murine tumor models and human cell lines potently cooperated with MEK inhibitors to kill these cancers through effects on eIF4E. We also demonstrated that MNK kinases are important and direct targets of cabozantinib. Accordingly, coadministration of cabozantinib and MEK inhibitors triggered dramatic regression in an aggressive genetically engineered tumor model. The cytotoxicity of this combination required the suppression of MNK-induced eIF4E phosphorylation and was not recapitulated by suppressing other cabozantinib targets. Collectively, these studies demonstrate that combined MNK and MEK suppression represents a promising therapeutic strategy for these incurable Ras-driven tumors and highlight the utility of developing selective MNK inhibitors for these and possibly other malignancies.

Imprime PGG-Mediated Anti-Cancer Immune Activation Requires Immune Complex Formation.

Imprime PGG (Imprime), an intravenously-administered, soluble ß-glucan, has shown compelling efficacy in multiple phase 2 clinical trials with tumor targeting or anti-angiogenic antibodies. Mechanistically, Imprime acts as pathogen-associated molecular pattern (PAMP) directly activating innate immune effector cells, triggering a coordinated anti-cancer immune response. Herein, using whole blood from healthy human subjects, we show that Imprime-induced anti-cancer functionality is dependent on immune complex formation with naturally-occurring, anti-ß glucan antibodies (ABA). The formation of Imprime-ABA complexes activates complement, primarily via the classical complement pathway, and is opsonized by iC3b. Immune complex binding depends upon Complement Receptor 3 and Fcg Receptor IIa, eliciting phenotypic activation of, and enhanced chemokine production by, neutrophils and monocytes, enabling these effector cells to kill antibody-opsonized tumor cells via the generation of reactive oxygen species and antibody-dependent cellular phagocytosis. Importantly, these innate immune cell changes were not evident in subjects with low ABA levels but could be rescued with exogenous ABA supplementation. Together, these data indicate that pre-existing ABA are essential for Imprime-mediated anti-cancer immune activation and suggest that pre-treatment ABA levels may provide a plausible patient selection biomarker to delineate patients most likely to benefit from Imprime-based therapy.

eIF-4E expression and its role in malignancies and metastases.

The contribution of the mRNA cap-binding protein, eIF-4E, to malignant transformation and progression has been illuminated over the past decade. eIF-4E overexpression has been demonstrated in human tumors of the breast, head and neck, colon, prostate, bladder, cervix and lung, and has been related to disease progression. Overexpression of eIF-4E in experimental models dramatically alters cellular morphology, enhances proliferation and induces cellular transformation, tumorigenesis and metastasis. Conversely, blocking eIF-4E function by expression of antisense RNA, or overexpression of the inhibitory eIF-4E binding proteins (4E-BPs), suppresses cellular transformation, tumor growth, tumor invasiveness and metastasis. Although eIF-4E regulates the recruitment of mRNA to ribosomes, and thereby globally regulates cap-dependent protein synthesis, eIF-4E contributes to malignancy by selectively enabling the translation of a limited pool of mRNAs--those that generally encode key proteins involved in cellular growth, angiogenesis, survival and malignancy (e.g. cyclin D1, c-myc, vascular endothelial growth factor, matrix metalloprotease 9). A deeper understanding of the role of eIF-4E in regulating the translation of the diverse gene products involved in all aspects of malignancy will improve the capacity to exploit eIF-4E as a therapeutic target and as a marker for human cancer progression.

Pak-1 expression increases with progression of colorectal carcinomas to metastasis.

PURPOSE: The p21-activated kinase-1 (Pak-1) promotes cell motility and invasiveness. Pak-1 is activated by the Rac, Rho, and Cdc42 small GTPases in response to a variety of stimuli including ras and phosphatidylinositol 3'-kinase/AKT pathway activation. Because Pak-1 plays a central role in regulating cell motility and invasiveness, we sought to determine whether Pak-1 may be involved in the malignant progression of colorectal carcinoma. EXPERIMENTAL DESIGN: Pak-1 expression was examined by immunohistochemistry in archived tissues from normal human colons, tubular and tubulovillous adenomas, invasive adenocarcinomas (stages I-III/IV), and lymph node metastases (184 total specimens from 38 patients). Specific cytoplasmic immunostaining was evaluated for overall intensity and uniformity to derive a combined histoscore (stain intensity x percentage of epithelium stained). RESULTS: Pak-1 expression was increased significantly with colorectal cancer progression from normal tissue to lymph node metastases (P < 0.0001). Furthermore, Pak-1 expression was increased significantly in adenomas, invasive carcinomas, and lymph node metastases compared with normal colon (P < 0.0001). Strikingly, Pak-1 expression was significantly higher in lymph node metastases than in invasive cancers, adenomas, or normal colon (P < 0.0001). Moreover, in patients with multiple lesions representing different stages of disease, Pak-1 expression was increased specifically in the most advanced lesions. CONCLUSIONS: This study demonstrates that Pak-1 expression is increased significantly with malignant progression of human colorectal carcinoma. These data, along with numerous functional studies demonstrating a central role for Pak-1 activity in tumor invasiveness and motility, implicate Pak-1 as an exciting target for therapy of colorectal carcinoma.

Targeting the eIF4F translation initiation complex: a critical nexus for cancer development.

Elevated protein synthesis is an important feature of many cancer cells and often arises as a consequence of increased signaling flux channeled to eukaryotic initiation factor 4F (eIF4F), the key regulator of the mRNA-ribosome recruitment phase of translation initiation. In many cellular and preclinical models of cancer, eIF4F deregulation results in changes in translational efficiency of specific mRNA classes. Importantly, many of these mRNAs code for proteins that potently regulate critical cellular processes, such as cell growth and proliferation, enhanced cell survival and cell migration that ultimately impinge on several hallmarks of cancer, including increased angiogenesis, deregulated growth control, enhanced cellular survival, epithelial-to-mesenchymal transition, invasion, and metastasis. By being positioned as the molecular nexus downstream of key oncogenic signaling pathways (e.g., Ras, PI3K/AKT/TOR, and MYC), eIF4F serves as a direct link between important steps in cancer development and translation initiation. Identification of mRNAs particularly responsive to elevated eIF4F activity that typifies tumorigenesis underscores the critical role of eIF4F in cancer and raises the exciting possibility of developing new-in-class small molecules targeting translation initiation as antineoplastic agents.

Translational control and metastatic progression: enhanced activity of the mRNA cap-binding protein eIF-4E selectively enhances translation of metastasis-related mRNAs.

To form metastases, tumors must break from the primary tumor site, invade surrounding tissues, enter and survive within the circulation and ultimately colonize a distal tissue. Each of these steps requires the cooperative function of numerous proteins--proteins that facilitate angiogenesis (e.g., VEGF), cell survival (e.g., Bcl-2), invasion (e.g., MMPs), and autocrine growth stimulation (e.g., c-myc, cyclin D1). Although expression of these proteins is regulated at many levels by disparate stimuli, translation of these key malignancy-related proteins is regulated primarily by the activity of the mRNA cap-binding protein eIF-4E, the rate-limiting member of the eIF-4F translation initiation complex. By binding the cap structure at the 5' terminus of cellular mRNAs, eIF-4E recruits mRNAs to the eIF-4F complex, which then scans from the 5' cap through the untranslated region (5'UTR), unwinding secondary structure to reveal the translation initiation codon and to enable ribosome loading. Messenger RNAs with short unstructured 5' UTRs are more easily translated than mRNAs harboring lengthy, highly structured 5' UTRs, as these prohibit efficient scanning and start codon recognition. As such, the translation of these mRNAs, which typically encode proteins involved in angiogenesis (e.g., VEGF), tumor growth (cyclin D1) and survival (Bcl-2), is suppressed except when eIF-4E is engaged with the eIF-4F complex--a common event in many human and experimental cancers. This review focuses on the hypothesis that enhanced eIF-4E function contributes to metastatic progression by selectively upregulating the translation of key malignancy-related proteins that together conspire to drive the metastatic process.

Emerging targets in the AKT pathway for treatment of androgen-independent prostatic adenocarcinoma.

Prostatic adenocarcinoma (CaP) is the most common, non-cutaneous malignancy and the second-leading cause of cancer death in men. The disease has two distinct phases: the androgen-dependent phase, which can be treated effectively with androgen ablation therapies, and the androgen-independent phase, for which there is no effective life-prolonging therapy. An estimated 32,000 men will die this year from androgen-independent, metastatic CaP. Efforts to understand the metastatic progression of CaP and the emergence of androgen-independent disease have begun to illuminate the molecular events involved. Recent work suggests that CaP progression to androgen-independent, metastatic disease involves a dampened apoptotic response, a release from the cell cycle block that initially follows androgen withdrawal and a shift from dependence on paracrine-derived growth and survival factors to autonomous production of these key proteins. Functional loss of the tumour suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) and subsequent activation of the AKT pathway, have been prominently implicated in the progression of CaP to androgen-independence. Activation of the AKT pathway can suppress the apoptotic response, undermine cell cycle control and selectively enhance the production of key growth and survival factors. Though many proteins and intracellular signalling pathways can influence these biological processes, activation of the AKT pathway may be a particularly potent signal involved in CaP progression to androgen-independence and therefore presents a series of potential targets for therapy of advanced androgen-independent CaP.

Expression levels of protein kinase C-alpha in non-small-cell lung cancer.

Current treatments of non-small-cell lung cancer (NSCLC) are inadequate and new therapies are being developed that target specific cellular signaling proteins associated with tumor growth. One potential target is protein kinase C (PKC)-alpha, a signaling molecule with an important role in cell regulation and proliferation. The present study examines the expression levels of PKC-alpha in NSCLC to better understand the distribution of PKC-alpha in NSCLC. We analyzed tumor specimens from an independent tumor tissue bank to determine PKC-alpha protein and messenger RNA gene expression in NSCLC. In addition, we used publicly available gene expression array data to further understand PKC-a-associated gene expression profiles in NSCLC. We found that PKC-alpha is highly expressed in < or = 20% of patients with NSCLC. We also found that PKC-alpha was preferentially expressed in adenocarcinoma compared with squamous cell carcinoma of the lung.

Pharmacogenetic inhibition of eIF4E-dependent Mmp9 mRNA translation reverses fragile X syndrome-like phenotypes.

Fragile X syndrome (FXS) is the leading genetic cause of autism. Mutations in Fmr1 (fragile X mental retardation 1 gene) engender exaggerated translation resulting in dendritic spine dysmorphogenesis, synaptic plasticity alterations, and behavioral deficits in mice, which are reminiscent of FXS phenotypes. Using postmortem brains from FXS patients and Fmr1 knockout mice (Fmr1(-/y)), we show that phosphorylation of the mRNA 5' cap binding protein, eukaryotic initiation factor 4E (eIF4E), is elevated concomitant with increased expression of matrix metalloproteinase 9 (MMP-9) protein. Genetic or pharmacological reduction of eIF4E phosphorylation rescued core behavioral deficits, synaptic plasticity alterations, and dendritic spine morphology defects via reducing exaggerated translation of Mmp9 mRNA in Fmr1(-/y) mice, whereas MMP-9 overexpression produced several FXS-like phenotypes. These results uncover a mechanism of regulation of synaptic function by translational control of Mmp-9 in FXS, which opens the possibility of new treatment avenues for the diverse neurological and psychiatric aspects of FXS.