Pazopanib in advanced germ cell tumors after chemotherapy failure: results of the open-label, single-arm, phase 2 Pazotest trial.

Background: Therapeutic options for patients with chemoresistant germ cell tumors (GCTs) are limited. Pazopanib is a selective tyrosine kinase inhibitor with distinct antiangiogenic activity. We aimed to evaluate pazopanib activity in patients with refractory GCT. Patients and methods: In the open-label, single-arm, phase 2 Pazotest study (NCT01743482), patient eligibility included failure of ≥2 platinum-based regimens, and allowed prior high-dose chemotherapy administration. Patients were given pazopanib 800 mg/day until disease progression (PD) or onset of unacceptable toxicity. Measurements of serum tumor markers (STM), computed tomography and FDG-PET were carried out at baseline, after 4 weeks of pazopanib treatment, and every 8 weeks thereafter. PD was defined as increasing levels of STM, increasing size of non-teratomatous masses, or appearance of new lesions. The study primary endpoint was progression-free survival (PFS, H0: 3-month PFS ≤ 10%, H1: ≥25%, α = 5%, ß = 20%). Results: Forty-three patients were enrolled from May 2013 to July 2016. The number of prior chemotherapy regimens was: 2 (11.6%), 3 (51.2%), >3 (37.2%). Grade 3 adverse events were observed in six patients (13.9%). Overall, 70.3% of patients had reduced levels of STM after 4 weeks. There were 2 partial responses (4.7%), 19 cases of stable disease, and 16 cases of PD (6 not evaluable by RECIST). The median follow-up duration was 29.6 months. The 3-month PFS probability was 12.8% [95% confidence interval (CI): 5.7%-28.9%]. The 24-month OS probability was 14.2% (95% CI: 6.0%-33.7%). In patients with a >50% decline in STM, the 24-month OS probability was 24.1% (95% CI: 8.3%-69.6%). The small sample size was the major limitation. Conclusions: Despite pazopanib showed potent but short-lived activity in refractory GCT, long-term survival was obtained in a proportion of treated patients. According to the kinetics of pazopanib activity, this drug may be investigated in less pre-treated patients as an optimal bridging therapy preceding and/or combined with salvage chemotherapy.

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 αvß3-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.

Analysis of plasma cytokines and angiogenic factors in patients with pretreated urothelial cancer receiving Pazopanib: the role of circulating interleukin-8 to enhance the prognostic accuracy.

BACKGROUND: Pazopanib achieved the end point of clinical activity in pretreated patients with urothelial cancer in a single-group, phase 2 trial. The objective was to identify biological predictors of clinical benefit to pazopanib in these patients. METHODS: EDTA blood samples were collected at baseline (T0) and after 4 weeks (T1) of treatment, together with radiological imaging in all 41 patients to analyse plasma circulating angiogenic factor levels by multiplex ELISA plates. Changes from T0 to T1 in marker levels were matched with response with the covariance analysis. Univariable and multivariable analyses evaluated the association with overall survival (OS), adjusted for prespecified clinical variables. Net reclassification improvement (NRI) tested the performance of the recognised Cox model. RESULTS: Increasing IL8(T1) level associated with lower response probability at covariance analysis (P=0.010). Both IL8(T0) (P=0.019) and IL8(T1) (P=0.004) associated with OS and the prognostic model, including clinical variables and IL8(T1) best-predicted OS after backward selection. The NRI for this model was 39%.When analysed as a time-varying covariate, IL8(T1) level<80 pg ml(-1) portended significantly greater response (∼80%) and 6-month OS (∼60%) probability than level ≥ 80. CONCLUSION: IL8-level changes during pazopanib allowed for a prognostic improvement and were associated with response probability.

Improved apoptotic cell death in drug-resistant non-small-cell lung cancer cells by tumor necrosis factor-related apoptosis-inducing ligand-based treatment.

Since response to platinum-based therapy in non-small-cell lung cancer (NSCLC) is poor, the present study was designed to rationally identify novel drug combinations in cell models including the A549 cell line and the cisplatin-resistant subline A549/Pt, characterized by reduced sensitivity to cisplatin-induced apoptosis and by upregulation of efflux transporters of the ATP binding cassette (ABC) superfamily. Given the molecular features of these cells, we focused on compounds triggering apoptosis through different mechanisms, such as the mitochondria-targeting drug arsenic trioxide and the phenanthridine analog sanguinarine, which induce apoptosis through the extrinsic pathway. Sanguinarine, not recognized by ABC transporters, could overcome cisplatin resistance and, when used in combination with arsenic trioxide, was synergistic in A549 and A549/Pt cells. The arsenic trioxide/sanguinarine cotreatment upregulated genes implicated in apoptosis activation through the extrinsic pathway. Drug combination experiments indicated that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) treatment improved arsenic trioxide/sanguinarine efficacy, a feature associated with a striking apoptosis induction, particularly in the cisplatin-resistant variant. Thus, a synergistic interaction between sanguinarine and arsenic trioxide could be obtained independent of relative cell sensitivity to arsenic trioxide, and an enhanced apoptosis induction could be achieved in combination with TRAIL through modulation of the extrinsic apoptotic pathway. Antitumor activity studies supported the interest of drug combinations including TRAIL in NSCLC, indicating that drug-resistant NSCLC cells can efficiently be killed by the combination of proapoptotic agents. Our results suggest that the molecular changes occurring in treated cells may be exploited to rationally hit surviving cells.

PF-03446962, a fully-human monoclonal antibody against transforming growth-factor ß (TGFß) receptor ALK1, in pre-treated patients with urothelial cancer: an open label, single-group, phase 2 trial.

Despite a compelling preclinical rationale for the use of anti-angiogenic drugs in urothelial cancer (UC), short-living responses have been observed in clinical trials. PF-03446962 is a novel monoclonal antibody against Activin Receptor-Like Kinase-1 (ALK1), a type I subclass of the TGFß receptor, with dose-dependent anti-angiogenic activity. An open label, single-group, phase 2 trial of PF-03446962 was conducted in salvage setting. Patients failing at least one chemotherapy regimen were eligible. Design provided PF-03446962 10 mg/Kg intravenously fortnightly until disease progression (PD) or unacceptable toxicity. Two-month progression-free survival (PFS) was the primary endpoint. The trial was registered with ClinicalTrials.gov, number NCT01620970. Fourteen patients were enrolled from October 2012 to July 2013. Median age was 64 years (interquartile range [IQR]: 58.2-69.5), 9 patients had a Bellmunt score of 1-2, median number of prior drugs was 3. One stable disease and 13 PD were recorded and the study met the futility stopping rule of interim analysis. Median PFS was 1.8 months (95 %CI, 1.4-2.0). After a median follow up of 7.4 months (IQR 4.5-10.9), 8 patients are alive. Median overall survival (OS) was 8 months (95 %CI, 2.9-not estimable). Most common toxicities were thrombocytopenia (G1-2 in 5 cases, persistent G3 in one, with 3 dose delays and 1 dose interruption), fatigue and abdominal pain (G1-2 in 4 cases each). Impairment of quality of life (ESAS score) was observed as well as an increase from baseline to +2 month median levels of vascular endothelial growth factor (VEGF) and interleukin-8. PF-03446962 had no activity as single drug in refractory UC and we do not recommend further investigation outside of the combination with agents targeting the VEGF receptor axis.

Sunitinib in advanced alveolar soft part sarcoma: evidence of a direct antitumor effect.

BACKGROUND: The purpose of this study was to confirm sunitinib activity in alveolar soft part sarcoma (ASPS) and to report on new insights into the molecular bases thereof. PATIENTS AND METHODS: From July 2007, nine patients with progressive metastatic ASPS received sunitinib 37.5 mg/day, within a named use program. Cryopreserved material was available for five naive patients, among whom three received sunitinib. Immunofluorescence (IF)/confocal microscopy, biochemical, and molecular/cytogenetic analyses were carried out, complemented by antiproliferative and activation assays in a short-term culture derived from one case. RESULTS: All patients were eligible for response. Best RECIST response was partial response in five cases, stable disease in three, and progression in one. The median progression-free survival was 17 months. Positron emission tomography results were consistent. Two cases of interval progressions were recorded. Antiproliferative assays and biochemistry on short-term culture showed that sunitinib is able to markedly impair ASPS cells growth and switch-off PDGFRB. IF/confocal microscopy demonstrated coexpression and physical association between PDGFRB/vascular endothelial growth factor receptor 2 (VEGFR2) and RET/VEGFR2 in ASPS cells, which was validated by biochemistry. PDGFRB, RET, and MET ligand-dependent activation was confirmed. CONCLUSIONS: We confirm the clinical efficacy of sunitinib in ASPS, mediated by PDGFRB, VEGFR2, and RET, which are all expressed in tumor cells. A direct antitumor effect was shown in a short-term cell culture.

Clinical prognostic factors in advanced epithelioid haemangioendothelioma: a retrospective case series analysis within the Italian Rare Cancers Network.

BACKGROUND: This multicentric, retrospective study conducted within the Italian Rare Cancer Network describes clinical features and explores their possible prognostic relevance in patients with advanced epithelioid haemangioendothelioma (EHE) started on surveillance. PATIENTS AND METHODS: We collected data on adult patients with molecularly confirmed, advanced EHE consecutively referred at five sarcoma reference centres between January 2010 and June 2018, with no evidence of progressive disease (PD) and started on surveillance. Overall survival (OS) and progression-free survival (PFS) univariable and multivariable Cox analyses were performed. In the latter, due to the low number of cases and events, penalized likelihood was applied, and variable selection was performed using a random forest model. RESULTS: Sixty-seven patients were included. With a median follow-up of 50.2 months, 51 (76%) patients developed PD and 16 (24%) remained stable. PD at treatment start did not meet RECIST version 1.1 in 15/51 (29%) patients. The 3-year PFS and OS were 25.4% and 71.1%, respectively, in the whole population. Tumour-related pain (TRP) was the most common baseline symptom (32.8%), followed by temperature (20.9%), fatigue (17.9%), and weight loss (16.4%). Baseline TRP (P = 0.0002), development of TRP during follow-up (P = 0.005), baseline temperature (P = 0.002), and development of fatigue during follow-up (P = 0.007) were associated with a significantly worst PFS. An association between baseline TRP (P < 0.0001), development of TRP during follow-up (P = 0.0009), evidence of baseline serosal effusion (P = 0.121), and OS was recorded. CONCLUSION: Because of the poor outcome observed in EHE patients presenting with serosal effusion, TRP, temperature, or serosal effusion, upfront treatment in this subgroup could be considered.

Apollon gene silencing induces apoptosis in breast cancer cells through p53 stabilisation and caspase-3 activation.

We analysed the effects of small interfering RNA (siRNA)-mediated silencing of Apollon, a member of the inhibitors of apoptosis protein family, on the proliferative potential and ability of human breast cancer cell lines to undergo apoptosis. In wild-type p53 ZR75.1 cells, Apollon knockdown resulted in a marked, time-dependent decline of cell growth and an increased rate of apoptosis, which was associated with p53 stabilisation and activation of the mitochondrial-dependent apoptotic pathway. Pre-incubation of cells with a p53-specific siRNA resulted in a partial rescue of cell growth inhibition, as well as in a marked reduction of the apoptotic response, indicating p53 as a major player in cell growth impairment consequent on Apollon silencing. Apollon knockdown induced consistently less pronounced anti-proliferative and pro-apoptotic effects in mutant p53 MDA-MB-231 cells than in ZR75.1 cells. Furthermore, the activation of caspase-3 seemed to be essential for the induction of apoptosis after Apollon knockdown, as the Apollon-specific siRNA had no effect on the viability of caspase-3-deficient, wild-type p53 MCF-7 cells or the ZR75.1 cells after RNA interference-mediated caspase-3 silencing. Our results indicate that p53 stabilisation and caspase-3 activation concur to determine the apoptotic response mediated by Apollon knockdown in breast cancer cells, and suggest Apollon to be a potential new therapeutic target for this malignancy.

Activity of axitinib in progressive advanced solitary fibrous tumour: Results from an exploratory, investigator-driven phase 2 clinical study.

BACKGROUND: To explore the activity of axitinib in advanced solitary fibrous tumour (SFT). PATIENTS AND METHODS: In this investigator-driven phase II study on axitinib in advanced and progressive SFT, patients received axitinib, 5 mg bis in day (BID), until progression or limiting toxicity. Pathologic diagnosis was centrally reviewed, distinguishing malignant SFT (M-SFT) and high-grade/dedifferentiated SFT (HG/D-SFT) subtypes. The primary end-point was the overall response rate (ORR) by Choi criteria (Choi). Secondary end-points were response by Response Evaluation Criteria in Solid Tumours (RECIST), progression-free survival (PFS) and overall survival (OS). RESULTS: From April 2015 and October 2017, 17 eligible patients entered the study (metastatic: 17; SFT subtype: 13 M-SFT, 4 HG/D-SFT; prior treatment: 9 antiangiogenics, 5 cytotoxics). All patients were evaluable for response. The best Choi response was seven partial response (PR) (ORR, 41.2%), six stable disease (SD) and four progressions. Choi-ORR was 54% (7/13) when only M-SFTs were considered. Four of seven responsive patients were pretreated with pazopanib. No responses were detected in HG/D-SFT. Best RECIST response was one PR (5.9%), 14 SD and two progressions. Toxicity was as expected. Median Choi-PFS was 5.1 (interquartile range [IQR]: 2.5-14.8) months. Median Choi-PFS was 14.8 (IQR: 5.1-18.0) and 2.8 (IQR: 2.0-5.9) months for patients responsive and non-responsive by Choi, respectively (p = 0.0416). At a 14.4-month median follow-up, median OS was 25.3 months. CONCLUSION: This study showed that axitinib is active in progressive advanced SFT. One-half of patients carrying the malignant variant of the disease responded, with a >12-month median progression arrest. Responses were better detected with Choi and seen even in patients resistant to other antiangiogenics. Tolerability was good.

High level of telomerase RNA gene expression is associated with chromatin modification, the ALT phenotype and poor prognosis in liposarcoma.

Telomere length is maintained by two known mechanisms, activation of telomerase or alternative lengthening of telomeres (ALT). The ALT pathway is more commonly activated in tumours of mesenchymal origin, although the mechanisms involved in the decision of a cell to activate either telomerase or ALT are unknown at present and no molecular markers exist to define the ALT phenotype. We have previously shown an association between chromatin remodelling, telomerase gene expression and ALT in cell line models. Here, we evaluate these findings and investigate their prognostic significance in a panel of liposarcoma tissue samples to understand the biology underlying the ALT phenotype. Liposarcoma samples were split into three groups: telomerase positive (Tel+); ALT positive; ALT-/Tel-. Differences in telomerase gene expression were evident between the groups with increased expression of hTR in ALT and Tel+ compared to ALT-/Tel- samples and increased hTERT in Tel+ samples only. Investigation of a small panel of chromatin modifications revealed significantly increased binding of acetyl H3 in association with hTR expression. We confirm that the presence of the ALT phenotype is associated with poor prognosis and in addition, for the first time, we show a direct association between hTR expression and poor prognosis in liposarcoma patients.

Patient-derived solitary fibrous tumour xenografts predict high sensitivity to doxorubicin/dacarbazine combination confirmed in the clinic and highlight the potential effectiveness of trabectedin or eribulin against this tumour.

BACKGROUND: Preclinical models that mimic pathological and molecular features of solitary fibrous tumour (SFT) represent an important tool to select effective regimes and novel compounds to be tested in the clinic. This study was aimed at developing two preclinical models of SFT, assessing their predictive value in the clinic and selecting potential novel effective treatments. MATERIAL AND METHODS: Two dedifferentiated-SFT (D-SFT) models obtained from patients' biopsies were grown in immunodeficient mice. The antitumour activity on these models of doxorubicin, dacarbazine (DTIC), ifosfamide (monotherapy or combination), trabectedin and eribulin was tested. Twelve SFT patients were treated with doxorubicin and DTIC. Response by RECIST, progression-free survival and overall survival were retrospectively evaluated, distinguishing malignant-SFT (M-SFT) and D-SFT. RESULTS: Two D-SFT patient-derived xenografts (PDXs) that represent the first available preclinical in vivo models of SFT were developed and characterised. Doxorubicin/DTIC, DTIC/ifosfamide, doxorubicin/ifosfamide combinations consistently induced better antitumour activity than the single-agents. Particularly, doxorubicin/DTIC combination caused a max tumour volume inhibition >80% in both models. Doxorubicin/DTIC combo showed activity also in the case-series. Best RECIST responses were: 6 responses (M-SFT = 2 of 7, D-SFT = 4 of 5), 1 stable disease, 5 progressions, with a 6-month median progression-free survival (M-SFT = 6, D-SFT = 10 months). The PDXs were very sensitive to trabectedin and eribulin. CONCLUSION: Doxorubicin plus DTIC combination was effective in our two D-SFT mice models and appeared to be active also in the clinic, especially in high-grade D-SFT patients. Among additional drugs tested in the PDXs, trabectedin and eribulin were highly effective, providing a rational to test these drugs in D-SFT patients.

Targeting telomerase by antisense-based approaches: perspectives for new anti-cancer therapies.

Oligonucleotide-based therapies have been under investigation for many years, and different antisense oligomers are being tested in clinical trials on patients with cancer and other diseases. Since telomerase reactivation has been defined as one of the six hallmarks of cancer because of the enzyme's ability to provide tumor cells with unlimited proliferative potential, antisense-based approaches, aimed to inhibit the core enzyme components, could represent innovative anticancer therapies. Overall, available information indicates antisense-based strategies as powerful tools to inhibit telomerase and interfere with tumor cell proliferative potential. Specifically, cancer cell growth arrest was observed in several tumor models as a consequence of telomere shortening in the presence of prolonged telomerase inhibition. However, in other studies, antisense-based treatments caused rapid loss of tumor cell viability and induced apoptosis independently of telomere attrition. The results would suggest that telomerase inhibition affects tumor cell growth by mechanisms that are dependent as well as independent of the enzyme telomere elongating activity. However, the role of telomerase in tumorigenesis and tumor progression, beyond the classical mechanism of telomere lengthening, needs to be further investigated to provide a better rationale for the design and development of antitelomerase-based therapies in clinical oncology.

Inhibition of telomerase activity by a hammerhead ribozyme targeting the RNA component of telomerase in human melanoma cells.

Reactivation of telomerase, an RNA-dependent DNA polymerase that synthesizes new telomeric repeats at the end of chromosomes, is a very common feature in human cancers. Telomerase is thought to be essential in maintaining the proliferative capacity of tumor cells and, as a consequence, it could represent an attractive target for new anti-cancer therapies. In this study, we generated a hammerhead ribozyme composed of a catalytic domain with flanking sequences complementary to the RNA component of human telomerase and designed to cleave specifically a site located at the end of the telomerase template sequence. In vitro the ribozyme induced cleavage of a synthetic RNA substrate obtained by cloning a portion of the RNA component of human telomerase. The extent of cleavage was dependent on the ribozyme/substrate ratio as well as the Mg2+ concentration. Moreover, when added to cell extracts from two human melanoma cell lines (JR8 and M14), or three melanoma surgical specimens, the ribozyme inhibited telomerase activity in a concentration- and time-dependent manner. When the ribozyme was delivered to growing JR8 melanoma cells by (N-(1-(2,3 dioleoxyloxy)propil)-N,N,N trimethylammonium methylsulfate-mediated transfer, a marked inhibition of telomerase activity was observed. Next, the ribozyme sequence was cloned in an expression vector and JR8 cells were transfected with it. The cell clones obtained showed a reduced telomerase activity and telomerase RNA levels and expressed the ribozyme. Moreover, ribozyme transfectants had significantly longer doubling times than control cells and showed a dendritic appearance in monolayer culture. No telomere shortening, however, was observed in these clones. Overall, our results indicate that the hammerhead ribozyme is a potentially useful tool for the inactivation of telomerase in human tumors.

Possible regulation of telomerase activity by transcription and alternative splicing of telomerase reverse transcriptase in human melanoma.

To investigate the regulatory mechanisms of telomerase activity in human melanoma cells, we assessed the enzyme's catalytic activity and the expression of the telomerase subunits, the human telomerase RNA, the human telomerase-associated protein, and the human telomerase reverse transcriptase, in 52 melanoma lesions. Eight normal skin specimens were also studied. Telomerase activity was detected in 84.6% of melanomas, whereas all skin specimens were telomerase negative. Human telomerase-associated protein mRNA and human telomerase RNA were constitutively expressed in all melanoma and skin specimens. Although at a variable level of expression, human telomerase reverse transcriptase mRNA was detected in all but one melanomas, whereas it was never present in skin samples. Reverse transcriptase-polymerase chain reaction experiments were performed using primers within the reverse transcriptase domain of human telomerase reverse transcriptase and revealed the presence of multiple alternatively spliced transcripts in melanoma specimens. Among the 44 telomerase-positive melanomas, one showed the full-length transcript alone whereas in all other specimens a full-length message was present with different combinations of alternatively spliced variants. In these tumors the expression of the full-length transcript was generally equal to or higher than that of the alternatively spliced variants. The ratio full-length transcript to alternatively spliced species ranged from 0.6 to 5.26, with a median value of 1.18. Among the seven telomerase-negative melanomas, one displayed the beta deletion transcript alone, whereas in the remaining six tumors weak expression of the full-length transcript and a more abundant level of alternatively spliced transcripts were found. In these cases human telomerase reverse transcriptase ratio ranged from 0.09 to 1.1, with a median value of 0.40. The results suggest that transcription and alternative splicing of human telomerase reverse transcriptase are regulatory mechanisms controlling telomerase activity in melanoma.

Effect of melphalan and hyperthermia on cell cycle progression and cyclin B1 expression in human melanoma cells.

We have investigated the effect of mild hyperthermia (42 degrees C) on the cytotoxic activity of a 1 h melphalan exposure in human melanoma cell lines. Hyperthermia did not affect cell growth of any culture, but it increased, to a different extent, melphalan cytotoxicity in all cell lines, with a reduction in the IC50 of 1.7 to 2.6-fold. Flow cytometric analysis showed that in normal temperature conditions melphalan caused S phase cell accumulation, which was evident only at 24 h in JR8, M14 and 2/21 cell lines and was still persistent at 72 h in 2/60 cells. Moreover, in all cell lines, the delay in S phase was paralleled, or followed, by an accumulation of cells in G2+M, which was transient in JR8 and M14 cells and persisted until 72 h in 2/21 and 2/60 melanoma clones. Hyperthermia caused a stabilization and prolongation of melphalan induced G2+M accumulation in JR8 and M14 cells. Conversely, in 2/21 and 2/60 clones, cell cycle perturbations induced by the drug were similar under normothermic or hyperthermic conditions. Specifically, in JR8, for which the maximum enhancement by hyperthermia on melphalan cytotoxicity was observed, cell accumulation in G2+M was still present 120 h after treatment. The accumulation was accompanied by an inhibition in the G2-M transition, as demonstrated by the significant reduction in the mitotic index of cells exposed to combined treatment compared to controls. Moreover, a bivariate distribution of cells stained for DNA and cyclin B1 showed that, following melphalan and hyperthermia treatment, the fraction of cyclin B1-expressing cells paralleled the fraction of G2+M phase cells, thus indicating that the inability of cells to enter mitosis was not ascribable to a reduction of cyclin B1 expression. On the whole, our results indicate that hyperthermia can stabilize the G2 accumulation induced by melphalan in human melanoma cells. Such a stabilization could contribute to the enhancement of melphalan cytotoxicity by heat, even though a strict correlation was not observed between the magnitude and persistence of the cell cycle perturbations and the extent of melphalan activity.

Inhibition of telomerase activity by a cell-penetrating peptide nucleic acid construct in human melanoma cells.

We investigated the effect of two peptide nucleic acids (PNAs), which are complementary to the RNA component of human telomerase, on the catalytic activity of the enzyme. PNAs induced a dose-dependent reduction of telomerase activity in cell extracts from human melanoma cell lines and surgical specimens. To down-regulate telomerase in intact cells, we generated a chimeric molecule synthesized by coupling the 13-mer PNA to the Antennapedia peptide. The PNA construct induced a dose- and time-dependent inhibition of telomerase activity. However, a 20-day exposure to the PNA construct only caused a slight increase in melanoma cell doubling time and failed to induce any telomere shortening.

Targeting human telomerase by antisense oligonucleotides and ribozymes.

Human telomerase is a ribonucleoprotein enzyme complex that enables cells to maintain telomere length, allowing indefinite replicative capacity. The notion that telomerase is reactivated in 80-90% of human cancers has led to the proposal of telomerase as a promising therapeutic target for novel anticancer interventions. Due to its inherent accessibility to nucleic acids, telomerase appears an ideal target for strategies based on the use of antisense oligonucleotides and ribozymes that target its RNA template. In this review a summary of the different antisense- and ribozyme-based approaches used thus far to inhibit telomerase activity in human cancer cells is provided. All these strategies significantly inhibited the enzyme's catalytic activity in in vitro and in vivo tumor models. However, while in some studies tumor cell growth arrest was observed as a consequence of telomere shortening after prolonged telomerase inhibition, other studies have shown that antisense- and ribozyme-based treatments targeting telomerase induced rapid loss (i.e. within a few days) of tumor cell viability with concomitant apoptosis. In the latter case it is unlikely that cell death was related to telomere erosion since the cells would not have undergone enough divisions to significantly shorten their telomeres. A possible explanation is that telomerase inhibitors may induce apoptosis in cancer cells directly by interfering with the capping function of the enzyme. Overall, the available results indicate antisense oligonucleotides and ribozymes as good tools to inhibit telomerase and suggest that abrogation of telomerase activity may affect tumor cell proliferation also through pathways that are not dependent on telomere erosion.

Attenuation of telomerase activity does not increase sensitivity of human melanoma cells to anticancer agents.

In tumour cells, replicative immortality is attained through stabilisation of telomeres by telomerase. Recent evidence suggests that telomerase plays an anti-apoptotic role. Since apoptosis is the primary mode of cell death induced by several drugs, telomerase could be involved in determining the chemosensitivity profile of tumour cells. We investigated whether inhibition of telomerase activity through a hammerhead ribozyme targeting the RNA template of telomerase influences the susceptibility of human melanoma cells to a variety of anticancer agents (platinum compounds, taxanes, topoisomerase I inhibitors). The ribozyme sequence was inserted into an expression vector and the JR8 human melanoma cell line was transfected with it. The cell clones obtained showed a reduced telomerase activity. Growth inhibition curves generated after exposure of ribozyme-transfectant clones to individual drugs were superimposable to those obtained from parental cells. Moreover, telomerase inhibition did not promote apoptosis as a cellular response to drug treatment. Overall, our results indicate that downregulation of telomerase activity does not increase the sensitivity of melanoma cells to anticancer drugs.

In vitro effect of lonidamine on the cytotoxicity of mitomycin C and BCNU in human colon adenocarcinoma cells.

The ability of lonidamine (LND), an energolytic derivative of indazole carboxylic acid, to modulate the cytotoxic activity of mitomycin C (MMC) and 1,3,bis(2-chloroethyl)-1-nitrosourea (BCNU) was investigated in two human adenocarcinoma cell lines (LoVo and HT29) expressing different sensitivity profiles to the drugs. After a 1-h treatment with MMC or BCNU, cells were postincubated for 24 h with 150-225 microM LND. In the LoVo cells, a synergistic interaction between LND and MMC or BCNU was observed at both LND concentrations. In HT29 cells, only additive effects of the drugs given in sequence were seen. Flow cytometric analysis indicated that LND was generally able to stabilise the cell cycle perturbations induced by MMC and BCNU in the two cell lines. The ability of LND to potentiate anticancer drug activity, and the consideration that LND causes side-effects different from those of conventional antitumour drugs, make this compound an attractive candidate for multidrug combination therapy in colon cancer.

Fludarabine as a modulator of cisplatin activity in human tumour primary cultures and established cell lines.

The potential of the purine analogue fludarabine (9-beta-D-arabinofuranosyl-2-fluoroadenine-5' monophosphate) as a modulator of cisplatin cytotoxicity was investigated in four established cell lines and 20 primary cultures of human melanoma and ovarian cancer. Tumour cells were exposed to fludarabine and cisplatin, alone or in combination, for 4 h. Fludarabine did not affect the growth of ovarian cancer cell lines, whereas it induced a marked and dose-dependent inhibition of proliferation in melanoma cell lines. In primary cultures of both histotypes, the purine analogue did not induce appreciable antiproliferative effects. Combined cisplatin-fludarabine treatment caused additive effects in all established cell lines. Conversely, a synergistic effect of the combination was seen in 5 of 10 melanoma and 4 of 10 ovarian cancer primary cultures, with a dose-modifying factor ranging from 2.1 to 3.9 for melanomas and from 4.0 to 7.5 for ovarian cancers, respectively. In the remaining cultures, the interaction between fludarabine and cisplatin was additive. The alkaline filter elution analysis performed on primary cultures showed that the synergistic interaction between the two drugs was paralleled by an increase in the extent and persistence of the cisplatin-induced DNA interstrand crosslinks. Our results indicate that fludarabine can enhance cisplatin cytotoxic activity in human tumour primary cultures from ovarian cancer and malignant melanoma. Such an effect may be partially due to an interference by fludarabine on cisplatin-induced DNA adduct metabolism and repair.