Synthetic sulfoglycolipids targeting the serine-threonine protein kinase Akt

The serine-threonine protein kinase Akt, also known as protein kinase B, is a key component of the phosphoinositide 3-kinase (PI3K)-Akt-mTOR axis. Deregulated activation of this pathway is frequent in human tumors and Akt-dependent signaling appears to be critical in cell survival. PI3K activation generates 3-phosphorylated phosphatidylinositols that bind Akt pleckstrin homology (PH) domain. The blockage of Akt PH domain/phosphoinositides interaction represents a promising approach to interfere with the oncogenic potential of over-activated Akt. In the present study, phosphatidyl inositol mimics based on a β-glucoside scaffold have been synthesized as Akt inhibitors. The compounds possessed one or two lipophilic moieties of different length at the anomeric position of glucose, and an acidic or basic group at C-6. Docking studies, ELISA Akt inhibition assays, and cellular assays on different cell models highlighted 1-O-octadecanoyl-2-O-β-d-sulfoquinovopyranosyl-sn-glycerol as the best Akt inhibitor among the synthesized compounds, which could be considered as a lead for further optimization in the design of Akt inhibitors.

Design, synthesis and biological evaluation of novel dimeric and tetrameric cRGD-paclitaxel conjugates for integrin-assisted drug delivery

Integrins are associated with tumour cell survival and progression, and their expression has been shown to be increased in tumours. Thus, four novel conjugates of the tripeptide integrin ligand Arg-Gly-Asp (RGD) and the cytotoxic agent paclitaxel (cRGD-PTX) were prepared to investigate the potential of the multivalent presentation of the RGD moiety in improving the antitumor efficacy of PTX by tumour targeting. PTX was conjugated to two or four integrin recognizing ligands. The influence of multivalent presentation on in vitro αvβ3-receptor affinity was confirmed. For all the conjugates compared to the previously synthesized monovalent counterparts, an enhancement of the binding strength was observed; this behaviour was more pronounced when considering the tetravalent presented RGD-conjugate. Cell growth inhibition assays on a panel of human tumour cell lines showed remarkable cytotoxic activity for all conjugates with IC50 values in a nanomolar range. Among the four conjugates, the bivalent derivative 3b was selected for in vivo studies in an ovarian carcinoma cell model xenografted in immunodeficient mice. A marked antitumor activity was observed, similar to that of PTX, but with a much more favourable toxicity profile. Overall, the novel cRGD-PTX conjugates disclosed here represent promising candidates for further advancement in the domain of targeted anti-tumour therapy.

Global metabolic profile identifies choline kinase alpha as a key regulator of glutathione-dependent antioxidant cell defense in ovarian carcinoma

Epithelial Ovarian Cancer (EOC) "cholinic phenotype", characterized by increased intracellular phosphocholine content sustained by over-expression/activity of choline kinase-alpha (ChoKα/CHKA), is a metabolic cellular reprogramming involved in chemoresistance with still unknown mechanisms.By stable CHKA silencing and global metabolic profiling here we demonstrate that CHKA knockdown hampers growth capability of EOC cell lines both in vitro and in xenotransplant in vivo models. It also affected antioxidant cellular defenses, decreasing glutathione and cysteine content while increasing intracellular levels of reactive oxygen species, overall sensitizing EOC cells to current chemotherapeutic regimens. Natural recovering of ChoKα expression after its transient silencing rescued the wild-type phenotype, restoring intracellular glutathione content and drug resistance. Rescue and phenocopy of siCHKA-related effects were also obtained by artificial modulation of glutathione levels. The direct relationship among CHKA expression, glutathione intracellular content and drug sensitivity was overall demonstrated in six different EOC cell lines but notably, siCHKA did not affect growth capability, glutathione metabolism and/or drug sensitivity of non-tumoral immortalized ovarian cells. The "cholinic phenotype", by recapitulating EOC addiction to glutathione content for the maintenance of the antioxidant defense, can be therefore considered a unique feature of cancer cells and a suitable target to improve chemotherapeutics efficacy.

Abstract B18: Association between apoptotic response and KiSS1 modulation in NSCLC preclinical models treated with SAHA and cisplatin

Non-Small-Cell Lung Cancer (NSCLC) is an aggressive disease with low responsiveness to chemotherapy. Platinum-based therapy is the standard of care for NSCLC with limited benefits due to the occurrence of resistance. Since histone deacetylases (HDAC) have been implicated in silencing of apoptotic pathways and failure to undergo apoptosis in response to antitumor agents may result in drug resistance, in the present study we examined the capability of SAHA (vorinostat), a pan-HDAC inhibitor to improve cisplatin-induced apoptosis in NSCLC models, focusing on the possible role of KiSS1, a well-known metastasis suppressor, which could be involved in apoptosis regulation.

Preclinical pharmacology approaches were employed including growth inhibition assays, western blot analyses, ELISA and antitumor activity tests in murine xenografts. The drug interaction was examined using the Bliss method.

We examined the effect of the combination of SAHA and cisplatin in the NSCLC H460 and A549 cell lines, including the cisplatin-resistant variants (H460/Pt, A549/Pt), which were found to exhibit enhanced invasive potential as compared to parental cells, besides reduced susceptibility to cisplatin-induced apoptosis. We observed that a synergistic interaction between SAHA and cisplatin occurred in cisplatin-sensitive H460 cells and in cisplatin-resistant H460/Pt cells, where it was less marked. The synergism was schedule-dependent because it was not observed following a simultaneous drug exposure, but when cells were pre-treated with SAHA for 24 h, a circumstance that we previously showed to up-regulate KiSS1 mRNA level. Under such a condition, increased levels of the pro-apoptotic protein Bax were detected by western blot analysis in cells exposed to the drug combination as compared to untreated and singly treated cells in both H460 and H460/Pt cells. Such a behaviour was associated with increased levels of apoptotic cells. Moreover, intracellular and extracellular levels of the KiSS1 protein tended to increase upon SAHA and combined treatment. In the A549 and A549/Pt cells an additive interaction was mainly observed. The efficacy of the combination was tested in vivo after subcutaneous inoculum of H460/Pt cells in immunodeficient mice. A significant tumor volume inhibition was found when mice bearing advanced tumors were treated with the combination of SAHA and cisplatin according to the best schedule identified in cellular studies.

Our findings indicate that the efficacy of the drug combination is schedule-dependent and may be influenced by the molecular background of the experimental models. The evidence of increased apoptosis in relation to KiSS1 up-modulation, together with previous findings of the involvement of KiSS1 in counteracting the invasive ability of NSCLC cells suggest a multi-tasking role for this factor.

Citation Format: Laura Gatti, Michelandrea De Cesare, Cristina Corno, Nives Carenini, Elisabetta Corna, Nadia Zaffaroni, Emilio Ciusani, Paola Perego. Association between apoptotic response and KiSS1 modulation in NSCLC preclinical models treated with SAHA and cisplatin. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B18.

Oxaliplatin in the era of personalized medicine: from mechanistic studies to clinical efficacy

Oxaliplatin is a third-generation platinum compound approved for clinical use relatively recently as compared to other drugs of the same class. Its main cellular target is DNA, where similarly to cisplatin and carboplatin it forms cross-links. However, due to a unique indication for colorectal cancer, synergistic interaction with fluoropyrimidines and peculiar toxicity profile, oxaliplatin is different from those compounds. Multiple lines of evidence indicate differences in transport and metabolism, consequences of DNA platination, as well as DNA repair and transduction of DNA damage. Here, we explore the preclinical features that may explain the unique properties of oxaliplatin in the clinics. Among them, the capability to accumulate in tumor cells via organic cation transporters, to kill KRAS mutant cells and to activate immunogenic cell death appears helpful to explain in part its clinical behavior. The continuous investigation of the molecular pharmacology of oxaliplatin is expected to provide clues to the definitions of predictors of drug activity and toxicity to translate to the clinical setting.

Microenvironment-Modulated Metastatic CD133+/CXCR4+/EpCAM- Lung Cancer-Initiating Cells Sustain Tumor Dissemination and Correlate with Poor Prognosis

Metastasis is the main reason for lung cancer-related mortality, but little is known about specific determinants of successful dissemination from primary tumors and metastasis initiation. Here, we show that CD133(+)/CXCR4(+) cancer-initiating cells (CIC) directly isolated from patient-derived xenografts (PDX) of non-small cell lung cancer are endowed with superior ability to seed and initiate metastasis at distant organs. We additionally report that CXCR4 inhibition successfully prevents the increase of cisplatin-resistant CD133(+)/CXCR4(+) cells in residual tumors and their metastatization. Immunophenotypic analysis of lung tumor cells intravenously injected or spontaneously disseminated to murine lungs demonstrated the survival advantage and increased colonization ability of a specific subset of CD133(+)/CXCR4(+) with reduced expression of epithelial cell adhesion molecule (EpCAM(-)), which also shows the greatest in vitro invasive potential. We next prove that recovered disseminated cells from lungs of PDX-bearing mice enriched for CD133(+)/CXCR4(+)/EpCAM(-) CICs are highly tumorigenic and metastatic. Importantly, microenvironment stimuli eliciting epithelial-to-mesenchymal transition, including signals from cancer-associated fibroblasts, are able to increase the dissemination potential of lung cancer cells through the generation of the CD133(+)/CXCR4(+)/EpCAM(-) subset. These findings also have correlates in patient samples where disseminating CICs are enriched in metastatic lymph nodes (20-fold, P = 0.006) and their detection in primary tumors is correlated with poor clinical outcome (disease-free survival: P = 0.03; overall survival: P = 0.05). Overall, these results highlight the importance of specific cellular subsets in the metastatic process, the need for in-depth characterization of disseminating tumor cells, and the potential of therapeutic strategies targeting both primary tumor and tumor-microenvironment interactions.

New mechanisms for old drugs: Insights into DNA-unrelated effects of platinum compounds and drug resistance determinants

Platinum drugs have been widely used for the treatment of several solid tumors. Although DNA has been recognized as the primary cellular target for these agents, there are unresolved issues concerning their effects and the molecular mechanisms underlying the antitumor efficacy. These cytotoxic agents interact with sub-cellular compartments other than the nucleus. Here, we review how such emerging phenomena contribute to the pharmacologic activity as well as to drug resistance phenotypes. DNA-unrelated effects of platinum drugs involve alterations at the plasma membrane and in endo-lysosomal compartments. A direct interaction with the mitochondria also appears to be implicated in drug-induced cell death. Moreover, the pioneering work of a few groups has shown that platinum drugs can act on the tumor microenvironment as well, and potentiate antitumor activity of the immune system. These poorly understood aspects of platinum drug activity sites may be harnessed to enhance their antitumor efficacy. A complete understanding of DNA-unrelated effects of platinum compounds might reveal new aspects of drug resistance allowing the implementation of the antitumor therapeutic efficacy of platinum compound-based regimens and minimization of their toxic side effects.

Histone deacetylase inhibitor-temozolomide co-treatment inhibits melanoma growth through suppression of Chemokine (C-C motif) ligand 2-driven signals

Target-specific agents used in melanoma are not curative, and chemokines are being implicated in drug-resistance to target-specific agents. Thus, the use of conventional agents in rationale combinations may result in optimization of therapy. Because histone deacetylases participate in tumor development and progression, the combination of the pan-inhibitor SAHA and temozolomide might provide a therapeutic advantage. Here, we show synergism between the two drugs in mutant BRAF cell lines, in association with decreased phosphorylation of cell survival proteins (e.g., C-Jun-N-terminal-kinase, JNK). In the spontaneous ret transgenic mouse melanoma model, combination therapy produced a significant disease onset delay and down-regulation of Chemokine (C-C motif) ligand 2 (CCL2), JNK, and of Myeloid-derived suppressor cell recruitment. Co-incubation with a CCL2-blocking-antibody enhanced in vitro cell sensitivity to temozolomide. Conversely, recombinant CCL2 activated JNK in human tumor melanoma cells. In keeping with these results, the combination of a JNK-inhibitor with temozolomide was synergistic. By showing that down-regulation of CCL2-driven signals by SAHA and temozolomide via JNK contributes to reduce melanoma growth, we provide a rationale for the therapeutic advantage of the drug combination. This combination strategy may be effective because of interference both with tumor cell and tumor microenvironment.

Profiling cancer gene mutations in longitudinal epithelial ovarian cancer biopsies by targeted next-generation sequencing: a retrospective study

BACKGROUND

The majority of patients with stage III-IV epithelial ovarian cancer (EOC) relapse after initially responding to platinum-based chemotherapy, and develop resistance. The genomic features involved in drug resistance are unknown. To unravel some of these features, we investigated the mutational profile of genes involved in pathways related to drug sensitivity in a cohort of matched tumors obtained at first surgery (Ft-S) and second surgery (Sd-S).

PATIENTS AND METHODS

Matched biopsies (33) taken at Ft-S and Sd-S were selected from the 'Pandora' tumor tissue collection. DNA libraries for 65 genes were generated using the TruSeq Custom Amplicon kit and sequenced on MiSeq (Illumina). Data were analyzed using a high-performance cluster computing platform (Cloud4CARE project) and independently validated.

RESULTS

A total of 2270 somatic mutations were identified (89.85% base substitutions 8.19% indels, and 1.92% unknown). Homologous recombination (HR) genes and TP53 were mutated in the majority of Ft-S, while ATM, ATR, TOP2A and TOP2B were mutated in the entire dataset. Only 2% of mutations were conserved between matched Ft-S and Sd-S. Mutations detected at second surgery clustered patients in two groups characterized by different mutational profiles in genes associated with HR, PI3K, miRNA biogenesis and signal transduction.

CONCLUSIONS

There was a low level of concordance between Ft-S and Sd-S in terms of mutations in genes involved in key processes of tumor growth and drug resistance. This result suggests the importance of future longitudinal analyses to improve the clinical management of relapsed EOC.

Anionic glycolipids related to glucuronosyldiacylglycerol inhibit protein kinase Akt

Long chain GlcADG analogues synthesized as PI3P mimics inhibited isolated Akt and proliferation of human ovarian carcinoma IGROV-1 cells.

p53-dependent activation of microRNA-34a in response to etoposide-induced DNA damage in osteosarcoma cell lines not impaired by dominant negative p53 expression

Osteosarcoma (OS) is the most common primary malignant bone tumor and prevalently occurs in the second decade of life. Etoposide, a chemotherapeutic agent used in combined treatments of recurrent human OS, belongs to the topoisomerase inhibitor family and causes DNA breakage. In this study we evaluated the cascade of events determined by etoposide-induced DNA damage in OS cell lines with different p53 status focusing on methylation status and expression of miR-34a that modulate tumor cell growth and cell cycle progression. Wild-type p53 U2-OS cells and U2-OS cells expressing dominant-negative form of p53 (U2- OS175) were more sensitive to etoposide than p53-deficient MG63 and Saos-2 cells, showing increased levels of unmethylated miR-34a, reduced expression of CDK4 and cell cycle arrest in G1 phase. In contrast, MG63 and Saos-2 cell lines presented aberrant methylation of miR-34a promoter gene with no miR-34a induction after etoposide treatment, underlining the close connection between p53 expression and miR-34a methylation status. Consistently, in p53siRNA transfected U2-OS cells we observed loss of miR-34a induction after etoposide exposure associated with a partial gain of gene methylation and cell cycle progress towards G2/M phase. Our results suggest that the open and unmethylated conformation of the miR-34a gene may be regulated by p53 able to bind the gene promoter. In conclusion, cell response to etoposide-induced DNA damage was not compromised in cells with dominant-negative p53 expression.

Nucleolar targeting by platinum: p53-independent apoptosis follows rRNA inhibition, cell-cycle arrest, and DNA compaction

TriplatinNC is a highly positively charged, substitution-inert derivative of the phase II clinical anticancer drug, BBR3464. Such substitution-inert complexes form a distinct subset of polynuclear platinum complexes (PPCs) interacting with DNA and other biomolecules through noncovalent interactions. Rapid cellular entry is facilitated via interaction with cell surface glycosoaminoglycans and is a mechanism unique to PPCs. Nanoscale secondary ion mass spectrometry (nanoSIMS) showed rapid distribution within cytoplasmic and nucleolar compartments, but not the nucleus. In this article, the downstream effects of nucleolar localization are described. In human colon carcinoma cells, HCT116, the production rate of 47S rRNA precursor transcripts was dramatically reduced as an early event after drug treatment. Transcriptional inhibition of rRNA was followed by a robust G₁ arrest, and activation of apoptotic proteins caspase-8, -9, and -3 and PARP-1 in a p53-independent manner. Using cell synchronization and flow cytometry, it was determined that cells treated while in G₁ arrest immediately, but cells treated in S or G₂ successfully complete mitosis. Twenty-four hours after treatment, the majority of cells finally arrest in G₁, but nearly one-third contained highly compacted DNA; a distinct biological feature that cannot be associated with mitosis, senescence, or apoptosis. This unique effect mirrored the efficient condensation of tRNA and DNA in cell-free systems. The combination of DNA compaction and apoptosis by TriplatinNC treatment conferred striking activity in platinum-resistant and/or p53 mutant or null cell lines. Taken together, our results support that the biological activity of TriplatinNC reflects reduced metabolic deactivation (substitution-inert compound not reactive to sulfur nucleophiles), high cellular accumulation, and novel consequences of high-affinity noncovalent DNA binding, producing a new profile and a further shift in the structure–activity paradigms for antitumor complexes.

Synergistic cooperation between sunitinib and cisplatin promotes apoptotic cell death in human medullary thyroid cancer

CONTEXT

Tyrosine kinase inhibitors represent a new treatment option for patients with advanced medullary thyroid cancer (MTC). However, cures have not been achieved with current available agents used in monotherapy.

OBJECTIVE

Because RET has been shown to negatively regulate CD95 death receptor activation in preclinical models of RET-dependent MTC, we investigated the potential of the combination approach with the RET-targeting tyrosine kinase inhibitor sunitinib and cisplatin to enhance apoptosis activation through the extrinsic pathway.

DESIGN

The effects of sunitinib and cisplatin were examined in human MTC cell lines harboring oncogenic RET mutations. Experiments were designed to determine drug effects on RET signaling, cell growth, apoptosis, autophagy, and tumor growth in mice and to investigate the mechanisms of the drug interaction.

RESULTS

Sunitinib and cisplatin synergistically inhibited the growth of MZ-CRC-1 cells harboring the RET M918T activating mutation. The combination enhanced apoptosis activation through CD95-mediated, caspase-8-dependent pathway. Moreover, sunitinib induced a severe perturbation of the autophagic flux characterized by autophagosome accumulation and a remarkable lysosomal dysfunction, which was further enhanced, with lysosomal leakage induction, by cisplatin. Administration of the drug combination to mice xenografted with MZ-CRC-1 cells improved the antitumor efficacy, as compared with single-agent treatments, inducing complete responses in 30% of the treated mice, a significant increase in caspase-3 activation (P < .01 vs cisplatin, and P < .0005 vs sunitinib) and apoptosis in tumor cells.

CONCLUSIONS

Addition of cisplatin to sunitinib potentiates apoptotic cell death and has promising preclinical activity in MTCs harboring the RET M918T oncogene.