Pharmacological inhibition of HSP90 and ras activity as a new strategy in the treatment of HNSCC.

Advanced head and neck squamous cell cancer (HNSCC) is currently treated with taxane-based chemotherapy. We have previously shown that docetaxel (DTX) induces a ras-dependent survival signal that can be antagonized by farnesyl transferase inhibitors (FTI) such as tipifarnib (TIP). Here we show that the synergistic TIP/DTX combination determines synergistic apoptotic conditions but, at the same time, it modulates the expression of the components of the multichaperone complex that is, in turn, involved in the regulation of the stability of members of the ras-mediated pathway. Therefore, we have stably transfected HNSCC KB and Hep-2 cells with a plasmid encoding for HSP90. The expression of the protein was increased in both transfected cell lines but its activation status was increased in Hep-2 clones and decreased in KB clones. On the basis of these results, we have treated both parental and HSP90-transfected cells with a HSP90 inhibitor geldanamycin (GA). We have found that the antiproliferative activity of GA is dependent upon the activation status of HSP90 and that it is strongly synergistic when added in combination with TIP but not with DTX in cells overexpressing HSP90 and even more in cells with increased HSP90 activity. These data were paralleled by the decreased expression and activity of the components belonging to the ras→mediated signal transduction pathway. The present results suggest that multichaperone complex activation could be a resistance mechanism to the anti-proliferative and apoptotic effects induced by TIP and that the combination of FTIs such as TIP with GA could be a suitable therapeutic strategy in the treatment of HSP90-overexpressing HNSCC.

Transglutaminases: key regulators of cancer metastasis.

The ability to metastasize represents the most important characteristic of malignant tumors. The biological details of the metastatic process remain somewhat unknown, due to difficulties in studying tumor cell behaviour with high spatial and temporal resolution in vivo. Several lines of evidence involve transglutaminases (TGs) in the key stages of tumor progression cascade, even though the molecular mechanisms remain controversial. TG expression and activity display a different role in the primary tumor or in metastatic cells. In fact, TG expression is low in the primary tumor mass, but augmented when cells acquire the metastatic phenotype. Nevertheless, in other cases, the use of inducers of TG transamidating activity seems to contrast tumor cell plasticity, migration and invasion. In the following review, the function of TGs in cancer cell migration into the extracellular matrix, adhesion to the capillary endothelium and its basement membrane, invasion and angiogenesis is discussed.

Role of endothelial nitric oxide synthase (eNOS) in chronic stress-promoted tumour growth.

Accumulating evidence suggests that chronic stress can be a cofactor for the initiation and progression of cancer. Here we evaluated the role of endothelial nitric oxide synthase (eNOS) in stress-promoted tumour growth of murine B16F10 melanoma cell line in C57BL/6 mice. Animals subjected to restraint stress showed increased levels adrenocorticotropic hormone, enlarged adrenal glands, reduced thymus weight and a 3.61-fold increase in tumour growth in respect to no-stressed animals. Tumour growth was significantly reduced in mice treated with the ß-antagonist propranolol. Tumour samples obtained from stressed mice displayed high levels of vascular endothelial growth factor (VEGF) protein in immunohistochemistry. Because VEGF can induce eNOS increase, and nitric oxide is a relevant factor in angiogenesis, we assessed the levels of eNOS protein by Western blot analysis. We found a significant increase in eNOS levels in tumour samples from stressed mice, indicating an involvement of this enzyme in stress-induced tumour growth. Accordingly, chronic stress did not promote tumour growth in eNOS(-/-) mice. These results disclose for the first time a pivotal role for eNOS in chronic stress-induced initiation and promotion of tumour growth.

Core-shell biodegradable nanoassemblies for the passive targeting of docetaxel: features, antiproliferative activity and in vivo toxicity.

Amphiphilic block copolymers of poly(ɛ-caprolactone) and poly(ethylene oxide) were assembled in core-shell nanoparticles (NPs) by a melting-sonication technique (MeSo). The entrapment of the poorly water-soluble anticancer drug docetaxel (DTX), nanocarrier cytotoxicity toward different cells and toxicity in mice were investigated. The encapsulation mechanism was rationalized and related to copolymer properties such as crystallinity and drug solubility in the copolymer phase. DTX release from NPs occurred in 2 drug pulses over 30 days. DTX entrapment in NPs strongly decreased haemolysis of erythrocytes in comparison with a commercial DTX formulation. In comparison with free DTX, NPs were both more efficient in inhibiting cell growth of breast and prostate cancer cells and less toxic in experimental animal models. The results of this study indicate that MeSo is an interesting technique for the achievement of peculiar core-shell nanocarriers for the passive targeting and sustained release of poorly water-soluble anticancer drugs. FROM THE CLINICAL EDITOR: In this study, stealth nanoparticles of PEO/PCL block copolymers for passive targeting of docetaxel to solid tumors were developed using a novel technique. The studied properties of NPs suggest strong potential as anticancer drug-delivery system.

Molecular targets and oxidative stress biomarkers in hepatocellular carcinoma: an overview.

Hepatocellular carcinoma (HCC) is a complex and heterogeneous tumor with multiple genetic aberrations. Several molecular pathways involved in the regulation of proliferation and cell death are implicated in the hepatocarcinogenesis. The major etiological factors for HCC are both hepatitis B virus (HBV) and hepatitis C virus infection (HCV). Continuous oxidative stress, which results from the generation of reactive oxygen species (ROS) by environmental factors or cellular mitochondrial dysfunction, has recently been associated with hepatocarcinogenesis. On the other hand, a distinctive pathological hallmark of HCC is a dramatic down-regulation of oxido-reductive enzymes that constitute the most important free radical scavenger systems represented by catalase, superoxide dismutase and glutathione peroxidase. The multikinase inhibitor sorafenib represents the most promising target agent that has undergone extensive investigation up to phase III clinical trials in patients with advanced HCC. The combination with other target-based agents could potentiate the clinical benefits obtained by sorafenib alone. In fact, a phase II multicenter study has demonstrated that the combination between sorafenib and octreotide LAR (So.LAR protocol) was active and well tolerated in advanced HCC patients. The detection of molecular factors predictive of response to anti-cancer agents such as sorafenib and the identification of mechanisms of resistance to anti-cancer agents may probably represent the direction to improve the treatment of HCC.

A new schedule of fotemustine in temozolomide-pretreated patients with relapsing glioblastoma.

In the present study we investigated the feasibility and effectiveness of a new biweekly schedule of fotemustine (FTM) in patients with recurrent glioblastoma, after at least one previous treatment. The primary endpoint was progression-free survival at 6 months; secondary objectives were clinical response, overall survival, disease-free survival, and toxicity. Forty patients (median age 52.8 years; median Karnofsky Performance Status at progression 90) underwent second-line chemotherapy with FTM. Selected patients were previously treated with a standard radiotherapy course with concomitant temozolomide (TMZ). After tumor relapse or progression proven by magnetic resonance imaging (MRI), all patients underwent chemotherapy with FTM, given intravenously at dose of 80 mg/m(2) every 2 weeks for five consecutive administrations (induction phase), and then every 4 weeks at 80 [DOSAGE ERROR CORRECTED] mg/m(2) as maintenance. A total of 329 infusions were administered; the median number of cycles administered was 8. All patients completed the induction phase, and 29 patients received at least one maintenance infusion. Response to treatment was assessed using MacDonald criteria. One complete response [2.5%, 95% confidence interval (CI): 0-10%], 9 partial responses (22.5%, 95% CI: 15-37%), and 16 stable diseases (40%, 95% CI: 32-51%) were observed. Median time to progression was 6.7 months (95% CI: 3.9-9.1 months). Progression-free survival at 6 months was 61%. Median survival from beginning of FTM chemotherapy was 11.1 months. The schedule was generally well tolerated; the main toxicities were hematologic (grade 3 thrombocytopenia in two cases). To the best of our knowledge, this is the first report specifically dealing with the use of a biweekly induction schedule of FTM. The study demonstrates that FTM has therapeutic efficacy as single-drug second-line chemotherapy with a favorable safety profile.

Nanotechnologies to use bisphosphonates as potent anticancer agents: the effects of zoledronic acid encapsulated into liposomes.

Zoledronic acid (ZOL) is a potent amino-bisphosphonate used for the treatment of bone metastases with recently reported antitumor activity. However, the short plasma half-life and rapid accumulation in bone limits the use of ZOL as an antitumor agent in extraskeletal tissues. Therefore, we developed stealth liposomes encapsulating ZOL (LipoZOL) to increase extraskeletal drug availability. Compared to free ZOL, LipoZOL induced a stronger inhibition of growth of a range of different cancer cell lines in vitro. LipoZOL also caused significantly larger inhibition of tumor growth and increased the overall survival in murine models of human prostate cancer and multiple myeloma, in comparison with ZOL. Moreover, a strong inhibition of vasculogenetic events without evidence of necrosis in the tumor xenografts from prostate cancer was recorded after treatment with LipoZOL. We demonstrated both antitumor activity and tolerability of LipoZOL in preclinical animal models of both solid and hematopoietic malignancies, providing a rationale for early exploration of use of LipoZOL as a potential anticancer agent in cancer patients. FROM THE CLINICAL EDITOR: The short plasma half-life and rapid accumulation in bone limits the use of zoledronic acid as an antitumor agent in extraskeletal tissues. Therefore, stealth liposomes encapsulating ZOL (LipoZOL) have been developed to increase extraskeletal drug availability.

Gamma-glutamyl 16-diaminopropane derivative of vasoactive intestinal peptide: a potent anti-oxidative agent for human epidermoid cancer cells.

We previously demonstrated that the gamma-glutamyl 16 amine derivative of vasoactive intestinal peptide (VIP) acts as structural VIP agonist with affinity and potency higher than VIP. Herein, we have evaluated the effects of VIP and gamma-Gln16-diaminopropane derivative of VIP (VIP-DAP3) on the proliferation and protection from oxidative stress induced by hydrogen peroxide (H2O2) on epidermoid carcinoma cell lines. We have found that 10(-11) M VIP-DAP3 completely antagonized the inhibition induced by H2O2 on both cell proliferation and S-phase distribution while these effects were only partially antagonized by equimolar concentrations of VIP. Moreover, both oxidative stress and intracellular lipid oxidation induced by H2O2 were reduced by VIP and completely antagonized by VIP-DAP3. Thereafter, we have found that H2O2 increased p38 kinase activity and both HSP70 and HSP27 expression. VIP and VIP-DAP3 again antagonized these effects partially or totally, respectively. H2O2 reduced the activity of extracellular signal-regulated kinases Erk-1/2 and Akt, signalling proteins involved in proliferation/survival pathways. Again VIP restored the activity of both kinases while VIP-DAP3 caused indeed an increase of their activity as compared to untreated cells. These data suggest that VIP-DAP3 has a stronger anti-oxidative activity as compared to VIP likely based on its super-agonistic binding on the putative receptor.

W7FW14F apomyoglobin amyloid aggregates-mediated apoptosis is due to oxidative stress and AKT inactivation caused by Ras and Rac.

We have previously reported that addition of prefibrillar aggregates (PFAs) derived from W7FW14F apomyoglobin mutant to NIH-3T3 cells affects their viability. In this article, we have found that cytotoxicity induced by PFAs in NIH 3T3 and SH-SY5Y human neuroblastoma cells was due to early activation of apoptotic cell death dependent from a caspase-3- and -9-mediated mitochondrial pathway. A time-dependent increase of intracellular ROS and an about twofold decrease of mitochondrial localization of scavenger protein MnSOD was found. The use of the anti-oxidant agent N-acetyl-cysteine (NAC) antagonized both the increase of intracellular ROS and apoptosis induced by PFAs. PFAs caused an about 60% increase of the activity of both Ras and Erk-1/2 at 30 and 45 min while they were restored to basal levels at later time points. This effect was paralleled by a time-dependent decrease of the activity of the survival enzyme Akt. Effects similar to those on Ras activity were also recorded on the activity of the stress involved small GTP binding protein Rac that was about 75% increased after 30 min but resumed to basal levels at later time points. This effect was paralleled by a time-dependent activation of p38 kinase activity and HSP-70 expression. The use of both the ras farnesyltransferase inhibitor tipifarnib and the Rac geranyl-geranyltransferase GGTI-298, but not of the MEK-1 inhibitor U0126 partially antagonized the effects of PFAs on apoptosis occurrence. On the other hand, the PI3K/Akt inhibitor LY 294002 potentiated apoptosis induced by PFAs. Our results indicate a role for Ras and Rac in the induction of both intracellular ROS increased levels and apoptosis mediated by PFAs and disclose a new scenario of intervention in neurodegenerative diseases.

Cyr61 downmodulation potentiates the anticancer effects of zoledronic acid in androgen-independent prostate cancer cells.

We have analyzed the gene modulation induced by zoledronic acid (ZOL) in androgen-resistant prostate cancer PC3 cells with cDNA microarray platform to identify new molecular targets of ZOL in prostate cancer. The gene coding for cysteine-rich, angiogenic inducer, 61 (CYR61) resulted highly downregulated with a fold change of 5.58. Therefore, we have studied the effects of ZOL on CYR61 protein product, and we have found that CYR61 protein expression was decreased significantly after exposure to ZOL. The effect of ZOL on CYR61 expression was dose and time dependent was due to a reduced transcriptional activity of CYR61 promoter. Moreover, the effects induced by ZOL were paralleled by decreased activation of Ras-Raf-1- and Akt-dependent pathways that was dependent from isoprenylation inhibition, since it was antagonized by the addition of geranylgeraniol. Finally, we have investigated the role of CYR61 in the regulation of growth inhibition and invasion/motility of PC3 cells using a shRNA for CYR61 to downregulate the expression of CYR61 protein. The enhanced inhibition of proliferation and motility/invasion induced by ZOL by S-phase accumulation. In the same experimental conditions, CYR61 protein downregulation potentiated the inactivation of the Ras-dependent proliferation pathway and cell cycle inhibitors p21 and p27 expression.

The farnesyltransferase inhibitor R115777 (ZARNESTRA) enhances the pro-apoptotic activity of interferon-alpha through the inhibition of multiple survival pathways.

Interferon alpha (IFNalpha) induces an EGF-Ras-->Raf-1-->Erk dependent survival pathway counteracting apoptosis induced by the cytokine. In this paper we have evaluated the effects of the combination between farnesyl-transferase inhibitor (FTI) R115777 and IFNalpha on the growth inhibition and apoptosis of cancer cells. Simultaneous exposure to R115777 and IFNalpha produced synergistic both antiproliferative and proapoptotic effects. In these experimental conditions, IFNalpha and R115777 completely antagonized the increased activity of both Ras and Erk-1/2 induced by IFNalpha and strongly reduced Akt activity. Furthermore, treatment with R115777 in combination with IFNalpha regimen induced tumor growth delay on established KB cell xenografts in nude mice, while the single agents were almost inactive. R115777 was again able to antagonize the Ras-dependent survival pathway induced by IFNalpha also in vivo. Raf-1, one of the downstream targets of Ras, has been reported to activate bcl-2 through displacement and/or phosphorylation of Bad. We have found that IFNalpha induced mitochondrial localization of Raf-1 that was antagonized by R115777. Moreover, IFNalpha increased Raf-1/bcl-2 immuno-conjugate formation and intracellular co-localization and enhanced phosphorylation of Bad at Ser 112 and again R115777 counteracted all these effects. Moreover, the use of plasmids encoding for dominant negative or dominant positive Raf-1 antagonized and potentiated, respectively, the co-immunoprecipitation between Raf-1 and bcl-2. In conclusion, FTI R115777 strongly potentiates the antitumor activity of IFNalpha both in vitro and in vivo through the inhibition of different survival pathways that are dependent from isoprenylation of intracellular proteins such as ras.

Change in TNF-alpha receptor expression is a relevant event in doxorubicin-induced H9c2 cardiomyocyte cell death.

Doxorubicin (Doxo) is a widely used anticancer drug given for the treatment of leukemias, lymphomas, and solid tumors. Despite its potent antitumor effects, the cardiotoxicity of this drug limits its clinical use. The biochemical mechanisms of Doxo-induced cardiotoxicity remain unclear. Doxo has been shown to induce apoptosis in cardiomyocytes that seems to be responsible, at least in part, for Doxo cardiotoxicity. In this study, we investigated tumor necrosis factor-alpha (TNF-alpha) receptor-mediated signaling to better understand the causes of Doxo-induced cardiotoxicity. Here, we report that Doxo is a potent inducer of apoptosis in both H9c2 cardiomyocytes and U2OS osteosarcoma tumor cells, with significant differences in terms of kinetics and caspase activation between the two cell lines. Interestingly, Doxo-induced apoptosis is accompanied by relevant changes in TNF-alpha receptor levels in H9c2 cardiomyocytes but not in U2OS cells. Moreover, treatment with exogenous TNF-alpha strongly potentiates the apoptotic effect of Doxo in H9c2 cardiomyocytes but not in U2OS cells. Our findings show that the function of TNF receptors I and II is affected by Doxo to ultimately modulate apoptosis and cell survival in H9c2 cardiomyocytes, reinforcing the recent evidence of the relevant role of TNF-alpha receptor-mediated signaling in cardiotoxicity induced by anthracyclines.

Effects of VIP and VIP-DAP on proliferation and lipid peroxidation metabolism in human KB cells.

In the present study, we have utilized the transglutaminase (TGase) enzyme to modify the primary structure of VIP with diaminopropane (DAP) at the level of the Gln16. We have investigated the conformational stability of VIP and VIP-DAP in solution by limited proteolysis experiments. The VIP-DAP appears to be more resistant to the proteolytic attack of trypsin, thus indicating that the derivatization in position 16 is able to stabilize the structure of the peptide. However, we have studied their role in cell cycle modulation and antioxidant activity in the oropharyngeal epidermoid carcinoma KB cells.

Phase II study of temozolomide plus pegylated liposomal doxorubicin in the treatment of brain metastases from solid tumours.

OBJECTIVE: A combination regimen of temozolomide (TMZ) and pegylated liposomal doxorubicin has been evaluated in the treatment of brain metastases from solid tumours. STUDY DESIGN: Nineteen consecutive patients (pts) have been enrolled in a prospective phase II trial and treated with TMZ 200 mg/m2 (days 1-5) and pegylated liposomal doxorubicin 35 mg/m2 (day 1) every 28 days. The study was prospectively projected according to the Simon's two-stage optimal design. RESULTS: Major toxicities have been grade III neutropenia and thrombocytopenia in one patient (pt) and grade III erythrodisesthesia in two pts. Three pts achieved a complete response (CR) and four a partial response (PR), for an overall response rate of 36.8% (95% CI: 19.1-59.2), which exceeded the target activity in the study design. A significant improvement in quality of life was demonstrated by FACT-G analysis. The median Progression Free Survival (PFS) was 5.5 (95% CI: 2.7-8.2) months while the median Overall Survival (OS) was 10.0 months (95% CI: 6.3-13.7). CONCLUSIONS: The TMZ/pegylated liposomal doxorubicin regimen was well tolerated with an encouraging activity in brain metastases from solid tumours.

The farnesyl transferase inhibitor R115777 (Zarnestra) synergistically enhances growth inhibition and apoptosis induced on epidermoid cancer cells by Zoledronic acid (Zometa) and Pamidronate.

Pamidronate (PAM) and zoledronic acid (ZOL) are aminobisphosphonates (BPs) able to affect the isoprenylation of intracellular small G proteins. We have investigated the antitumor activity of BPs and R115777 farnesyl transferase inhibitor (FTI) against epidermoid cancer cells. In human epidermoid head and neck KB and lung H1355 cancer cells, 48 h exposure to PAM and ZOL induced growth inhibition (IC(50) 25 and 10 microM, respectively) and apoptosis and abolished the proliferative and antiapoptotic stimuli induced by epidermal growth factor (EGF). In these experimental conditions, ZOL induced apoptosis through the activation of caspase 3 and a clear fragmentation of PARP was also demonstrated. A strong decrease of basal ras activity and an antagonism on its stimulation by EGF was recorded in the tumor cells exposed to BPs. These effects were paralleled by impaired activation of the survival enzymes extracellular signal regulated kinase 1 and 2 (Erk-1/2) and Akt that were not restored by EGF. Conversely, farnesol induced a recovery of ras activity and antagonized the proapoptotic effects induced by BPs. The combined treatment with BPs and R115777 resulted in a strong synergism both in growth inhibition and apoptosis in KB and H1355 cells. The synergistic activity between the drugs allowed BPs to produce tumor cell growth inhibition and apoptosis at in vivo achievable concentrations (0.1 micromolar for both drugs). Moreover, the combination was highly effective in the inhibition of ras, Erk and Akt activity, while farnesol again antagonized these effects. In conclusion, the combination of BPs and FTI leads to enhanced antitumor activity at clinically achievable drug concentrations that resides in the inhibition of farnesylation-dependent survival pathways and warrants further studies for clinical translation.

Chemotherapy regimen GOLF induces apoptosis in colon cancer cells through multi-chaperone complex inactivation and increased Raf-1 ubiquitin-dependent degradation.

The multi-drug combination of oxaliplatin (OXA), 5-Fluorouracil (5-FU) and leucovorin (LF) is currently considered as the gold standard treatment for metastatic colorectal carcinoma. In previous studies, we have studied a chemotherapy regimen containing gemcitabine (GEM), OXA, LF, and 5-FU (named GOLF regimen) that has shown a good safety profile and highly significant anti-tumor activity. In the present study, we have investigated on the anti-tumour mechanisms of GOLF in human colon cancer HT-29 and WiDr cell lines. We have found that GOLF induced growth inhibition that was largely caused by apoptosis differently from other combinations. Moreover, the different drugs composing GOLF were highly synergistic in inducing growth inhibition. Apoptosis induced by GOLF combination was paralleled by PARP cleavage and caspase 9 and 3 activation that were not recorded in the other combinations. An about 85% decrease of the activity of Erk and Akt was found in GOLF-treated cells. These effects were likely due to decreased expression of the upstream activator Raf-1 and of Akt itself, respectively. The intracellular levels of these signalling components can be post-translationally regulated by ubiquitin-dependent degradation through proteasome. Therefore, we have evaluated the expression of some chaperone components and we have found that GOLF did not affect the expression of both heat shock protein (HSP) 90 and 27 but induced an about 90% increase of HSP70 levels suggesting the inactivation of the multi-chaperone complex. Moreover, an about 4-fold increase of the ubiquitination of Raf-1 was also found and the addition for 12 h of 10 microM proteasome inhibitor lactacystin caused an accumulation of the ubiquitinated isoforms of Raf-1. In conclusions, GOLF was a combination highly synergistic in inducing both growth inhibition and apoptosis of colon cancer cells. These effects likely occurred through the disruption of critical survival pathways and the inactivation of multi-chaperone complex.

Prognostic role of bcl-xL and p53 in childhood acute lymphoblastic leukemia (ALL).

Molecular parameters involved in the prediction of response of childhood acute lymphoblastic leukemia (ALL) are still unclear. We have evaluated the expression and mutational status of p53 and the expression of bcl-x(L) and bax in a series of 62 consecutive children (median age: 4 years; 38 males and 24 females) affected by de novo ALL. Alterations and overexpression of p53 were uncommon events (9/62, 14.5%) while bcl-x(L) and bax overexpression were frequent (about 70%). EFS was directly correlated to age<6 years (p=0.0178), nonT phenotype (p=0.0470), WBC at diagnosis

Alpha-interferon and its effects on signalling pathways within cells.

Interferon-alpha (IFNalpha) is a recombinant protein widely used in the therapy of several neoplasms such as myeloma, renal cell carcinoma, epidermoid cervical and head and neck tumours and melanoma. IFNalpha, the first cytokine to be produced by recombinant DNA technology, has emerged as an important regulator of cancer cell growth and differentiation, affecting cellular communication and signal transduction pathways. However, the way by which tumour cell growth is directly suppressed by IFNalpha is not well known. Wide evidence exists on the possibility that cancer cells undergo apoptosis after the exposure to the cytokine. Here we will review the consolidate Signal transducer and activator of transcription (STAT)-dependent mechanism of action of IFNalpha and the supposed mechanism of apoptosis induction by IFNalpha. We will discuss data obtained by us and others on the triggering of the stress-dependent kinase pathway and on the modulation of protein synthesis machinery induced by IFNalpha and their correlations with the apoptotic process. Until today, inconsistent data have been obtained regarding the clinical effectiveness of IFNalpha in the therapy of solid tumours. In fact, the benefit of IFNalpha treatment is limited to some neoplasms while others are completely or partially resistant. The mechanisms of tumour resistance to IFNalpha have been studied in vitro. The alteration of JAK- Signal transducer and activator of transcription components of the IFNalpha-induced signalling, can be indeed a mechanism of resistance to IFN and cross talks between IFNalpha and survival signals has been also described. However, we have recently described a reactive mechanism of protection of tumour cells from the apoptosis induced by IFNalpha dependent on the epidermal growth factor (EGF)-mediated Ras/extracellular signal regulated kinase (Erk) signalling. The involvement of the Ras->Erk pathway in the protection of tumour cells from the apoptosis induced by IFNalpha is further demonstrated by both Ras inactivation by RASN17 transfection and mitogen extracellular signal regulated kinase 1 (Mek-1) inhibition by exposure to PD098059. These data strongly suggest that the specific disruption of the latter could be a useful approach to potentiate the antitumour activity of IFNalpha against human tumours based on the new mechanistic insights achieved in the last years.

Glucocorticoids induce G1 arrest of lymphoblastic cells through retinoblastoma protein Rb1 dephosphorylation in childhood acute lymphoblastic leukemia in vivo.

Childhood Acute Lymphoblastic Leukemia (ALL) represents approximately 40% of pediatric cancers, but molecular mechanisms involved in the therapeutic resistance of ALL are still unclear. The disregulation of cell cycle could be a mechanism of progression of leukemic blasts and glucocorticoids (GCs), the main pharmacological agent in the treatment of ALL, could affect cell cycle distribution. In our study we have evaluated cell cycle distribution and the expression of several molecules involved in cell cycle regulation in blasts collected from 32 patients with ALL before and 48 h after treatment with GCs. A significant increase of the percentage of ALL blasts in G(0)/G(1) phase was recorded after treatment with GCs in 22 (69%) out of 32 patients and 18 of these patients were also good responders to GC therapy. In these patients an increase of the expression of at least one of the 4 evaluated CDKIs (p15, p16, p21 and p27) was found in 29 out of 32 patients (90.6%) without any change in CDK2 and 4 expression. All patients expressed detectable levels of Rb-1 phosphorylation at the diagnosis. Twenty (63%) patients showed a decrease, while two patients showed an increase of p110 Rb-1 phosphorylation and no changes were detected in the remaining 10 patients after GC therapy. The univariate analysis showed that the reduction of pRb-1 phosphorylation was significantly higher in B-cell lineage patients and in good responders. In conclusion, this is the first report that evaluate the Rb-1 function as predictor of response in childhood ALL and our data suggest that its hypophosphorylation and, consequently, reduced activity correlates with a statistical significance with the responsiveness to GC therapy. These results suggest that Rb-1 can be a useful molecular target for the therapy of this subset of patients.