Reducing MYC's transcriptional footprint unveils a good prognostic gene signature in melanoma

MYC's key role in oncogenesis and tumor progression has long been established for most human cancers. In melanoma, its deregulated activity by amplification of 8q24 chromosome or by upstream signaling coming from activating mutations in the RAS/RAF/MAPK pathway-the most predominantly mutated pathway in this disease-turns MYC into not only a driver but also a facilitator of melanoma progression, with documented effects leading to an aggressive clinical course and resistance to targeted therapy. Here, by making use of Omomyc, the most characterized MYC inhibitor to date that has just successfully completed a phase I clinical trial, we show for the first time that MYC inhibition in melanoma induces remarkable transcriptional modulation, resulting in severely compromised tumor growth and a clear abrogation of metastatic capacity independently of the driver mutation. By reducing MYC's transcriptional footprint in melanoma, Omomyc elicits gene expression profiles remarkably similar to those of patients with good prognosis, underlining the therapeutic potential that such an approach could eventually have in the clinic in this dismal disease.

Abstract 3435: Identification of potential biomarkers of response to OMO-103, a first-in-modality pan-MYC inhibitor, in patients with advanced solid tumors

Background: MYC is a key transcription factor driving and maintaining human tumors. Since MYC has long been perceived as an “undruggable” target, to date, there is still no MYC inhibitor approved for clinical use. However, we designed and validated Omomyc, a MYC dominant negative mini-protein, demonstrating its potent therapeutic impact in various mouse models of cancer. Importantly, a Phase 1 study testing OMO-103, an Omomyc-based mini-protein developed by Peptomyc S.L., was successfully completed in 2022. Here, we present the main findings of the study and associated biomarker program.

Material and Methods: A phase I dose escalation study was performed in all-comers solid tumor patients, with a 3+3 design of 6 dose levels ranging from 0.48 to 9.72mg/kg, as a weekly 30-min i.v. infusion. Tumor and liquid biopsies were collected at screening, upon and at the end of treatment, to assess different biomarkers of drug activity.

Results: 22 patients with advanced solid tumors were included and 18 patients were considered evaluable for response by CT scan. Of these, 9 achieved SD. The PK analysis revealed a plasma half-life of >40h. No ADAs were detected in any of the patients. Drug pharmacodynamics supported target engagement, as demonstrated by Digital Spatial Profiling analysis showing shut down of MYC transcriptional signature in patients’ tumor biopsies. In addition, a distinctive pharmacodynamic cytokine signature that correlated with stable disease was found through liquid biopsies already 3 to 4 weeks before CT scan. Importantly, a cytokine signature was also identified as being predictive of disease stabilization at baseline and could help stratify patients in upcoming additional clinical studies. Finally, several anti-tumor immune related markers were also found modulated upon OMO-103 treatment.

Conclusion: OMO-103 demonstrates a favorable safety profile, with encouraging signs of activity supported by predictive and pharmacodynamic biomarkers worthy of further investigation.

Citation Format: Marie-Eve Beaulieu, Elena Garralda, Sílvia Casacuberta-Serra, Sandra Sandra Martínez-Martín, Emiliano Calvo, Víctor Moreno, Sergio López-Estévez, Laia Foradada, Guzman Alonso, Elena Corral, Bernard Doger, Tatiana Hernández, Judit Grueso, Íñigo Íñigo González-Larreategui, Erika Serrano del Pozo, Hugo Thabussot, Virginia Castillo Cano, Mariano F. Mariano F. Zacarías-Fluck, Jastrinjan Kaur, Fabio Giuntini, Jonathan R. Whitfield, Josefa Morales, Manuela Niewel, Laura Soucek. Identification of potential biomarkers of response to OMO-103, a first-in-modality pan-MYC inhibitor, in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3435.

Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance

PURPOSE

PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR)-deficient tumors and are used to treat breast, ovarian, pancreatic, and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor (WEE1i) combination demonstrated enhanced antitumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance.

EXPERIMENTAL DESIGN

We analyzed breast and ovarian patient-derived xenoimplant models resistant to PARPi to quantify WEE1i and ATR inhibitor (ATRi) responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models.

RESULTS

Although WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress.

CONCLUSIONS

Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.

High p16 expression and heterozygous RB1 loss are biomarkers for CDK4/6 inhibitor resistance in ER+ breast cancer

CDK4/6 inhibitors combined with endocrine therapy have demonstrated higher antitumor activity than endocrine therapy alone for the treatment of advanced estrogen receptor-positive breast cancer. Some of these tumors are de novo resistant to CDK4/6 inhibitors and others develop acquired resistance. Here, we show that p16 overexpression is associated with reduced antitumor activity of CDK4/6 inhibitors in patient-derived xenografts (n = 37) and estrogen receptor-positive breast cancer cell lines, as well as reduced response of early and advanced breast cancer patients to CDK4/6 inhibitors (n = 89). We also identified heterozygous RB1 loss as biomarker of acquired resistance and poor clinical outcome. Combination of the CDK4/6 inhibitor ribociclib with the PI3K inhibitor alpelisib showed antitumor activity in estrogen receptor-positive non-basal-like breast cancer patient-derived xenografts, independently of PIK3CA, ESR1 or RB1 mutation, also in drug de-escalation experiments or omitting endocrine therapy. Our results offer insights into predicting primary/acquired resistance to CDK4/6 inhibitors and post-progression therapeutic strategies.

Preclinical In Vivo Validation of the RAD51 Test for Identification of Homologous Recombination-Deficient Tumors and Patient Stratification

PARP inhibitors (PARPi) are approved drugs for platinum-sensitive, high-grade serous ovarian cancer (HGSOC) and for breast, prostate, and pancreatic cancers (PaC) harboring genetic alterations impairing homologous recombination repair (HRR). Detection of nuclear RAD51 foci in tumor cells is a marker of HRR functionality, and we previously established a test to detect RAD51 nuclear foci. Here, we aimed to validate the RAD51 score cut off and compare the performance of this test to other HRR deficiency (HRD) detection methods. Laboratory models from BRCA1/BRCA2-associated breast cancer, HGSOC, and PaC were developed and evaluated for their response to PARPi and cisplatin. HRD in these models and patient samples was evaluated by DNA sequencing of HRR genes, genomic HRD tests, and RAD51 foci detection. We established patient-derived xenograft models from breast cancer (n = 103), HGSOC (n = 4), and PaC (n = 2) that recapitulated patient HRD status and treatment response. The RAD51 test showed higher accuracy than HRR gene mutations and genomic HRD analysis for predicting PARPi response (95%, 67%, and 71%, respectively). RAD51 detection captured dynamic changes in HRR status upon acquisition of PARPi resistance. The accuracy of the RAD51 test was similar to HRR gene mutations for predicting platinum response. The predefined RAD51 score cut off was validated, and the high predictive value of the RAD51 test in preclinical models was confirmed. These results collectively support pursuing clinical assessment of the RAD51 test in patient samples from randomized trials testing PARPi or platinum-based therapies.

SIGNIFICANCE

This work demonstrates the high accuracy of a histopathology-based test based on the detection of RAD51 nuclear foci in predicting response to PARPi and cisplatin.

High FGFR1-4 mRNA expression levels correlate with response to selective FGFR inhibitors in breast cancer

PURPOSE

FGFR1 amplification (FGFR1amp) is recurrent in metastatic breast cancer (BC) and is associated with resistance to endocrine therapy (ET) and CDK4/6 inhibitors (CDK4/6i). Multi-tyrosine kinase inhibitors (MTKI) and selective pan-FGFR inhibitors (FGFRi) are being developed for FGFR1amp BC. High-level FGFR amplification and protein expression by IHC have identified BC responders to FGFRi or MTKI, respectively.

EXPERIMENTAL DESIGN

Here, we used preclinical models and patient samples to identify predictive biomarkers to these drugs. We evaluated the antitumor activity of an FGFRi and an MTKI in a collection of seventeen BC patient-derived xenografts (PDXs) harboring amplification in FGFR1/2/3/4 and in ten patients receiving either an FGFRi/MTKI. mRNA levels were measured on FFPE tumor samples using two commercial strategies. Proliferation and angiogenesis were evaluated by detecting Ki-67 and CD31 in viable areas by immunofluorescence.

RESULTS

High FGFR1-4 mRNA levels but not copy number alteration (CNA) associated with FGFRi response. Treatment with MTKI showed higher response rates than with FGFRi (86% vs 53%), regardless of the FGFR1-4 mRNA levels. FGFR-addicted PDXs exhibited an antiproliferative response to either FGFRi or MTKI, and PDXs exclusively sensitive to MTKI exhibited an additional anti-angiogenic response. Consistently, clinical benefit of MTKI was not associated with high FGFR1-4 mRNA levels and it was observed in patients previously treated with anti-angiogenic drugs.

CONCLUSION

Tailored therapy with FGFRi in molecularly-selected metastatic BC based on high FGFR1-4 mRNA levels warrants prospective validation in luminal BC CDK4/6i-resistant patients and in TNBC patients without targeted therapeutic options.

PI3K activation promotes resistance to eribulin in HER2-negative breast cancer

BACKGROUND

Eribulin is a microtubule-targeting agent approved for the treatment of advanced or metastatic breast cancer (BC) previously treated with anthracycline- and taxane-based regimens. PIK3CA mutation is associated with worse response to chemotherapy in oestrogen receptor-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic BC. We aimed to evaluate the role of phosphoinositide 3-kinase (PI3K)/AKT pathway mutations in eribulin resistance.

METHODS

Resistance to eribulin was evaluated in HER2- BC cell lines and patient-derived tumour xenografts, and correlated with a mutation in the PI3K/AKT pathway.

RESULTS

Eleven out of 23 HER2- BC xenografts treated with eribulin exhibited disease progression. No correlation with ER status was detected. Among the resistant models, 64% carried mutations in PIK3CA, PIK3R1 or AKT1, but only 17% among the sensitive xenografts (P = 0.036). We observed that eribulin treatment induced AKT phosphorylation in vitro and in patient tumours. In agreement, the addition of PI3K inhibitors reversed primary and acquired resistance to eribulin in xenograft models, regardless of the genetic alterations in PI3K/AKT pathway or ER status. Mechanistically, PI3K blockade reduced p21 levels likely enabling apoptosis, thus sensitising to eribulin treatment.

CONCLUSIONS

PI3K pathway activation induces primary resistance or early adaptation to eribulin, supporting the combination of PI3K inhibitors and eribulin for the treatment of HER2- BC patients.

Genetic Alterations in the PI3K/AKT Pathway and Baseline AKT Activity Define AKT Inhibitor Sensitivity in Breast Cancer Patient-derived Xenografts

PURPOSE

AZD5363/capivasertib is a pan-AKT catalytic inhibitor with promising activity in combination with paclitaxel in triple-negative metastatic breast cancer harboring PI3K/AKT-pathway alterations and in estrogen receptor-positive breast cancer in combination with fulvestrant. Here, we aimed to identify response biomarkers and uncover mechanisms of resistance to AZD5363 and its combination with paclitaxel.

EXPERIMENTAL DESIGN

Genetic and proteomic markers were analyzed in 28 HER2-negative patient-derived xenografts (PDXs) and in patient samples, and correlated to AZD5363 sensitivity as single agent and in combination with paclitaxel.

RESULTS

Four PDX were derived from patients receiving AZD5363 in the clinic which exhibited concordant treatment response. Mutations in PIK3CA/AKT1 and absence of mTOR complex 1 (mTORC1)-activating alterations, for example, in MTOR or TSC1, were associated with sensitivity to AZD5363 monotherapy. Interestingly, excluding PTEN from the composite biomarker increased its accuracy from 64% to 89%. Moreover, resistant PDXs exhibited low baseline pAKT S473 and residual pS6 S235 upon treatment, suggesting that parallel pathways bypass AKT/S6K1 signaling in these models. We identified two mechanisms of acquired resistance to AZD5363: cyclin D1 overexpression and loss of AKT1 p.E17K.

CONCLUSIONS

This study provides insight into putative predictive biomarkers of response and acquired resistance to AZD5363 in HER2-negative metastatic breast cancer.

STK11 (LKB1) missense somatic mutant isoforms promote tumor growth, motility and inflammation

Elucidating the contribution of somatic mutations to cancer is essential for personalized medicine. STK11 (LKB1) appears to be inactivated in human cancer. However, somatic missense mutations also occur, and the role/s of these alterations to this disease remain unknown. Here, we investigated the contribution of four missense LKB1 somatic mutations in tumor biology. Three out of the four mutants lost their tumor suppressor capabilities and showed deficient kinase activity. The remaining mutant retained the enzymatic activity of wild type LKB1, but induced increased cell motility. Mechanistically, LKB1 mutants resulted in differential gene expression of genes encoding vesicle trafficking regulating molecules, adhesion molecules and cytokines. The differentially regulated genes correlated with protein networks identified through comparative secretome analysis. Notably, three mutant isoforms promoted tumor growth, and one induced inflammation-like features together with dysregulated levels of cytokines. These findings uncover oncogenic roles of LKB1 somatic mutations, and will aid in further understanding their contributions to cancer development and progression.

Paula Granado-Martínez, Sara Ortega, Elena González-Sánchez et al. report a functional analysis of four cancer-associated mutant isoforms of the gene STK11 using cell-based and animal models. They find the mutant isoforms no longer show tumor suppressor activity, promote tumor growth, and affect the regulation of cytokines and genes involved in vesicle trafficking.

A RAD51 assay feasible in routine tumor samples calls PARP inhibitor response beyond BRCA mutation

Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) are effective in cancers with defective homologous recombination DNA repair (HRR), including BRCA1/2-related cancers. A test to identify additional HRR-deficient tumors will help to extend their use in new indications. We evaluated the activity of the PARPi olaparib in patient-derived tumor xenografts (PDXs) from breast cancer (BC) patients and investigated mechanisms of sensitivity through exome sequencing, BRCA1 promoter methylation analysis, and immunostaining of HRR proteins, including RAD51 nuclear foci. In an independent BC PDX panel, the predictive capacity of the RAD51 score and the homologous recombination deficiency (HRD) score were compared. To examine the clinical feasibility of the RAD51 assay, we scored archival breast tumor samples, including PALB2-related hereditary cancers. The RAD51 score was highly discriminative of PARPi sensitivity versus PARPi resistance in BC PDXs and outperformed the genomic test. In clinical samples, all PALB2-related tumors were classified as HRR-deficient by the RAD51 score. The functional biomarker RAD51 enables the identification of PARPi-sensitive BC and broadens the population who may benefit from this therapy beyond BRCA1/2-related cancers.

Abstract 3596: Biomarkers of response to CDK4/6 inhibitor (CDK4/6i) in hormone receptor (HR) positive and HER2-positive breast cancer (BC) patient-derived xenografts (PDX)

The cell cycle G1-restriction point is frequently deregulated in HR+ BC by alterations of cyclin D1 (CCND1), p16 (CDKN2A) or pRb (RB1). CDK4/6i (ribociclib, abemaciclib and palbociclib) have shown clinical activity in metastatic HR+ BC, both as single agents and in combination with endocrine therapy. Currently, no biomarkers of response to CDK4/6i have been identified beyond HR expression and little is known about mechanisms of acquired resistance.

Twenty-one PDXs were established from HR+, HER2+ or HR+/HER2+ BC patient biopsies and their response to ribociclib was evaluated in vivo and ex vivo in matrigel cultures. Acquired-resistance was generated in vivo by isolating tumors that escaped therapy overtime. In order to identify response biomarkers, genetic and proteomic analysis of PDXs were performed and correlated with ribociclib antitumor activity. Candidates were validated in a cohort of 8 tumor samples from patients treated with abemaciclib monotherapy and in vitro. Combination with the PI3K-alpha inhibitor (PI3Ki) BYL719 was explored in vivo.

In vivo, ribociclib exhibited antitumor activity in five out of 21 PDXs (24%), two of which acquired resistance after continuous dosage (75mg/kg, 6IW). Ex vivo matrigel cultures recapitulated the in vivo response with 75% sensitivity and 92% specificity (p=0.01), providing a novel approach for high throughput screening. Baseline levels of ER, PR and Ki67 protein or PIK3CA/ESR1 mutations did not discriminate between ribociclib-resistant/sensitive PDXs, whereas CCND1/D2-amplification/overexpression were only found in ribociclib-resistant models. Importantly, sensitive PDXs exhibited significant Ki67 reduction upon ribociclib treatment, higher baseline pRb- and lower p16-staining compared to ribociclib-resistant PDXs (p=0.004, 0.02 and 0.03, respectively). Three out of 8 acquired-resistant tumors (37.5%) exhibited pRb loss. In vitro, RB1 knockdown and cyclin D1/D2-overexpression resulted in higher BrdU incorporation and higher IC50 than control cells upon ribociclib treatment. p16 expression was significantly lower in samples of patients exhibiting clinical benefit with abemaciclib monotherapy (p=0.04). Remarkably, combination of ribociclib with a PI3Ki resulted in appreciable antitumor activity in 18 out of 20 PDXs (90%), including two models resistant to fulvestrant given in combination with ribociclib.

In conclusion, HR+, HER2+ and HR+/HER2+ BC PDXs expressing both high Rb- and low p16-protein levels are sensitive to CDK4/6i whereas deregulation of the G1-restriction point due to low pRb or high cyclin D1/D2 protein levels is associated with resistance to ribociclib monotherapy. Addition of a PI3Ki markedly improves the antitumor response of ribociclib in most of PDXs, suggesting that the PI3K pathway may play a pivotal role in limiting the efficacy of CDK4/6 inhibition.

Citation Format: Marta Palafox, María Teresa Herrera-Abreu, Meritxell Bellet, Mafalda Oliveira, Alejandra Bruna, Olga Rodriguez, Marta Guzmán, Judit Grueso, Cristina Vilaplana, Joaquín Arribas, Emmanuelle di Tomaso, Faye Su, Carlos Caldas, Nicholas C. Turner, Rodrigo Dienstmann, José Baselga, Maurizio Scaltriti, Javier Cortés, Cristina Saura, Violeta Serra. Biomarkers of response to CDK4/6 inhibitor (CDK4/6i) in hormone receptor (HR) positive and HER2-positive breast cancer (BC) patient-derived xenografts (PDX) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3596.

RAD51 foci as a functional biomarker of homologous recombination repair and PARP inhibitor resistance in germline BRCA-mutated breast cancer

Background

BRCA1 and BRCA2 (BRCA1/2)-deficient tumors display impaired homologous recombination repair (HRR) and enhanced sensitivity to DNA damaging agents or to poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi). Their efficacy in germline BRCA1/2 (gBRCA1/2)-mutated metastatic breast cancers has been recently confirmed in clinical trials. Numerous mechanisms of PARPi resistance have been described, whose clinical relevance in gBRCA-mutated breast cancer is unknown. This highlights the need to identify functional biomarkers to better predict PARPi sensitivity.

Patients and methods

We investigated the in vivo mechanisms of PARPi resistance in gBRCA1 patient-derived tumor xenografts (PDXs) exhibiting differential response to PARPi. Analysis included exome sequencing and immunostaining of DNA damage response proteins to functionally evaluate HRR. Findings were validated in a retrospective sample set from gBRCA1/2-cancer patients treated with PARPi.

Results

RAD51 nuclear foci, a surrogate marker of HRR functionality, were the only common feature in PDX and patient samples with primary or acquired PARPi resistance. Consistently, low RAD51 was associated with objective response to PARPi. Evaluation of the RAD51 biomarker in untreated tumors was feasible due to endogenous DNA damage. In PARPi-resistant gBRCA1 PDXs, genetic analysis found no in-frame secondary mutations, but BRCA1 hypomorphic proteins in 60% of the models, TP53BP1-loss in 20% and RAD51-amplification in one sample, none mutually exclusive. Conversely, one of three PARPi-resistant gBRCA2 tumors displayed BRCA2 restoration by exome sequencing. In PDXs, PARPi resistance could be reverted upon combination of a PARPi with an ataxia-telangiectasia mutated (ATM) inhibitor.

Conclusion

Detection of RAD51 foci in gBRCA tumors correlates with PARPi resistance regardless of the underlying mechanism restoring HRR function. This is a promising biomarker to be used in the clinic to better select patients for PARPi therapy. Our study also supports the clinical development of PARPi combinations such as those with ATM inhibitors.

Abstract 150: Identification of determinants of sensitivity to AKT inhibition using breast cancer (BC) patient-derived tumor xenografts (PDX)

The antitumor activity of AKT inhibitors is being investigated for the treatment of BC with activation of the PI3K/AKT pathway. Putative predictive biomarkers that are being tested in ongoing trials are PTEN loss/mutation (mut) (around 40% of triple negative BC) and AKT1 mutation (4-5% ER+/HER2- BC). The BEECH trial is evaluating the activity of the pan-AKT1/2/3 inhibitor (AKTi) AZD5363 in combination with the antimicrotubule agent paclitaxel in HER2-negative (HER2-) metastatic BC. We aimed to identify response biomarkers to the single agent AKTi and its degree of synergy in combination with paclitaxel, using HER2- patient-derived tumor xenografts (PDX).

Fifteen PDX have been established from BC patients receiving standard treatment at our Hospital, as well as from those participating in the BEECH trial, when sample was available, by implanting their tumor biopsies at baseline, on-treatment and at progression. The antitumor activity of AZD5363 as single agent and in combination with paclitaxel has been measured in these PDX. Genotyping and protein levels have been analyzed by exome sequencing, capture-based sequencing, Western blot and immunohistochemistry (IHC).

AZD5363 monotherapy results in disease stabilization or tumor regression in 3 out of 15 PDX (2/9 ER-/HER2- and 1/6 ER+/HER2-). We found a positive association between high levels of pAKT S473 by Western blot and antitumor response. Interestingly, the two ER-/HER2- responding PDX harbor a PTEN frameshift mutation or gene loss concomitant with an activating mutation within the PI3K pathway (PIK3CA or PIK3R1). The ER+/HER2- PDX responder harbors an AKT1-p.E17K mutation. AZD5363 plus paclitaxel, at a clinically relevant dose, results in disease stabilization in 2/11 PDX that progress to either single agent (1/7 ER-/HER2- and 1/4 ER+/HER2-); the latter PDX being derived from the baseline tumor biopsy of a BEECH trial patient who benefited from this combination for one year.

Altogether these results suggest that double-altering events in the PI3K pathway, including PTEN loss/mut and a second PI3K-pathway alteration in ER-/HER2- tumors, or AKT1-p.E17K in ER+/HER2- tumors, and consequent high pAkt S473 levels could be associated with intrinsic sensitivity to AKT inhibition. The predictive value of these alterations as determinants of response to AKTi deserves further investigation.

Citation Format: Albert Gris-Oliver, Mafalda Oliveira, Marta Guzman, Olga Rodríguez, Judit Grueso, Maurizio Scaltriti, William J. Howat, J Carl Barrett, Javier Cortés, José Baselga, Gaia Schiavon, Barry R. Davies, Cristina Saura, Violeta Serra. Identification of determinants of sensitivity to AKT inhibition using breast cancer (BC) patient-derived tumor xenografts (PDX) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 150. doi:10.1158/1538-7445.AM2017-150

Resolution of hydrops fetalis caused by atrioventricular block: good postnatal evolution with terbutaline treatment

INTRODUCTION

Complete atrioventricular block (CAVB) is rarely seen, as it occurs in only 1:11 000 to 1:20 000 newborns. There is a serious risk of mortality in CAVB, mainly in those cases associated with hydrops, fetal cardiac frequency ≤ 55 beats/minute, and premature delivery.

CASE REPORT

Case of complete atrioventricular block with a poor prognosis (hydrops fetalis and foetal cardiac frequency < 5 beats/minute) caused by anti-La and anti-Ro antibodies. Intrauterine symptoms improved after treatment with terbutaline, permit- ting foetal viability and successful postnatal treatment with a cardiac pacemaker.

DISCUSSION

In case of complete atrioventricular block of cause autoimmune with poor prognosis should be treated with positive inotropic drugs, anticholinergics or b-mimetic in the attempt to maintain adequate ventricular frequency, and thus prevent hydrops fetalis from occurring.

Cancer network activity associated with therapeutic response and synergism

Background

Cancer patients often show no or only modest benefit from a given therapy. This major problem in oncology is generally attributed to the lack of specific predictive biomarkers, yet a global measure of cancer cell activity may support a comprehensive mechanistic understanding of therapy efficacy. We reasoned that network analysis of omic data could help to achieve this goal.

Methods

A measure of “cancer network activity” (CNA) was implemented based on a previously defined network feature of communicability. The network nodes and edges corresponded to human proteins and experimentally identified interactions, respectively. The edges were weighted proportionally to the expression of the genes encoding for the corresponding proteins and relative to the number of direct interactors. The gene expression data corresponded to the basal conditions of 595 human cancer cell lines. Therapeutic responses corresponded to the impairment of cell viability measured by the half maximal inhibitory concentration (IC₅₀) of 130 drugs approved or under clinical development. Gene ontology, signaling pathway, and transcription factor-binding annotations were taken from public repositories. Predicted synergies were assessed by determining the viability of four breast cancer cell lines and by applying two different analytical methods.

Results

The effects of drug classes were associated with CNAs formed by different cell lines. CNAs also differentiate target families and effector pathways. Proteins that occupy a central position in the network largely contribute to CNA. Known key cancer-associated biological processes, signaling pathways, and master regulators also contribute to CNA. Moreover, the major cancer drivers frequently mediate CNA and therapeutic differences. Cell-based assays centered on these differences and using uncorrelated drug effects reveals novel synergistic combinations for the treatment of breast cancer dependent on PI3K-mTOR signaling.

Conclusions

Cancer therapeutic responses can be predicted on the basis of a systems-level analysis of molecular interactions and gene expression. Fundamental cancer processes, pathways, and drivers contribute to this feature, which can also be exploited to predict precise synergistic drug combinations.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0340-x) contains supplementary material, which is available to authorized users.

Abstract 2825: Identification of CDK4/6-response biomarkers using estrogen receptor-positive breast cancer patient-derived xenografts (PDX)

Endocrine resistance is a clinical challenge for the treatment of estrogen receptor positive (ER+) breast cancer (BC). CDK4/6 blockade in combination with endocrine therapy has shown clinical activity in metastatic ER+ BC refractory to anti-hormonal treatment. However, there is a need for biomarkers that can predict the response to this treatment and improve patient stratification. We aimed to address this issue using xenograft models established from samples of ER+ BC patients.

Six ER+ PDXs were treated with continuous doses of a CDK4/6 inhibitor (LEE011, 75mg/kg, 6IW) and a PI3K-alpha inhibitor (BYL719, 35mg/kg, 6IW) as single agents and in combination, and intrinsic sensitivity to these agents was evaluated. The models were then genomically characterized using a capture-based sequencing panel and by digital PCR.

One PDX model was intrinsically sensitive to single-agent CDK4/6 inhibition and experienced tumor regression, but all individual tumors eventually escaped therapy after 50 days of treatment. This particular model harbored an ESR1-mutation and concomitant losses of CDKN2A/B. At relapse, we identified the acquisition of an RB1 frameshift mutation. Interestingly, upfront combined treatment with a PI3K-alpha inhibitor delayed the onset of tumor progression. Two out of the remaining five CDK4/6-resistant PDXs harbored either a frameshift mutation in RB1 (plus loss of heterozygosity) or had low pRb protein expression. Two other resistant models harbored CCND1 and MYC amplifications. The remaining one harbored a TSC1 loss. In all the CDK4/6-resistant PDX, however, the combination of CDK4/6 and PI3K-alpha inhibition resulted in tumor regression.

From our results, we conclude that loss of G1-cell cycle checkpoint control, such as mutation/loss of RB1 and CCND1-amplification, is associated with lack of response to CDK4/6 blockade in ER+ BC PDX. The addition of a PI3K-alpha inhibitor results in improvement of disease control in all experimental models tested.

Citation Format: Violeta Serra, Marta Palafox, Maria-Teresa Herrera, Martin A Rivas, Marta Guzmán, Olga Rodriguez, Judit Grueso, Meritxell Bellet, Mafalda Oliveira, Cristina Saura, Emmanuelle di Tomaso, Giordi Camponigro, Nicholas C. Turner, Javier Cortés, José Baselga. Identification of CDK4/6-response biomarkers using estrogen receptor-positive breast cancer patient-derived xenografts (PDX). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2825.

Early Adaptation and Acquired Resistance to CDK4/6 Inhibition in Estrogen Receptor-Positive Breast Cancer

Small-molecule inhibitors of the CDK4/6 cell-cycle kinases have shown clinical efficacy in estrogen receptor (ER)-positive metastatic breast cancer, although their cytostatic effects are limited by primary and acquired resistance. Here we report that ER-positive breast cancer cells can adapt quickly to CDK4/6 inhibition and evade cytostasis, in part, via noncanonical cyclin D1-CDK2-mediated S-phase entry. This adaptation was prevented by cotreatment with hormone therapies or PI3K inhibitors, which reduced the levels of cyclin D1 (CCND1) and other G1-S cyclins, abolished pRb phosphorylation, and inhibited activation of S-phase transcriptional programs. Combined targeting of both CDK4/6 and PI3K triggered cancer cell apoptosis in vitro and in patient-derived tumor xenograft (PDX) models, resulting in tumor regression and improved disease control. Furthermore, a triple combination of endocrine therapy, CDK4/6, and PI3K inhibition was more effective than paired combinations, provoking rapid tumor regressions in a PDX model. Mechanistic investigations showed that acquired resistance to CDK4/6 inhibition resulted from bypass of cyclin D1-CDK4/6 dependency through selection of CCNE1 amplification or RB1 loss. Notably, although PI3K inhibitors could prevent resistance to CDK4/6 inhibitors, they failed to resensitize cells once resistance had been acquired. However, we found that cells acquiring resistance to CDK4/6 inhibitors due to CCNE1 amplification could be resensitized by targeting CDK2. Overall, our results illustrate convergent mechanisms of early adaptation and acquired resistance to CDK4/6 inhibitors that enable alternate means of S-phase entry, highlighting strategies to prevent the acquisition of therapeutic resistance to these agents. Cancer Res; 76(8); 2301-13. ©2016 AACR.

PI3K inhibition results in enhanced estrogen receptor function and dependence in hormone receptor-positive breast cancer

Activating mutations of PIK3CA are the most frequent genomic alterations in estrogen receptor (ER)-positive breast tumors, and selective phosphatidylinositol 3-kinase α (PI3Kα) inhibitors are in clinical development. The activity of these agents, however, is not homogeneous, and only a fraction of patients bearing PIK3CA-mutant ER-positive tumors benefit from single-agent administration. Searching for mechanisms of resistance, we observed that suppression of PI3K signaling results in induction of ER-dependent transcriptional activity, as demonstrated by changes in expression of genes containing ER-binding sites and increased occupancy by the ER of promoter regions of up-regulated genes. Furthermore, expression of ESR1 mRNA and ER protein were also increased upon PI3K inhibition. These changes in gene expression were confirmed in vivo in xenografts and patient-derived models and in tumors from patients undergoing treatment with the PI3Kα inhibitor BYL719. The observed effects on transcription were enhanced by the addition of estradiol and suppressed by the anti-ER therapies fulvestrant and tamoxifen. Fulvestrant markedly sensitized ER-positive tumors to PI3Kα inhibition, resulting in major tumor regressions in vivo. We propose that increased ER transcriptional activity may be a reactive mechanism that limits the activity of PI3K inhibitors and that combined PI3K and ER inhibition is a rational approach to target these tumors.

MEK plus PI3K/mTORC1/2 Therapeutic Efficacy Is Impacted by TP53 Mutation in Preclinical Models of Colorectal Cancer

PURPOSE

PI3K pathway activation occurs in concomitance with RAS/BRAF mutations in colorectal cancer, limiting the sensitivity to targeted therapies. Several clinical studies are being conducted to test the tolerability and clinical activity of dual MEK and PI3K pathway blockade in solid tumors.

EXPERIMENTAL DESIGN

In the present study, we explored the efficacy of dual pathway blockade in colorectal cancer preclinical models harboring concomitant activation of the ERK and PI3K pathways. Moreover, we investigated if TP53 mutation affects the response to this therapy.

RESULTS

Dual MEK and mTORC1/2 blockade resulted in synergistic antiproliferative effects in cell lines bearing alterations in KRAS/BRAF and PIK3CA/PTEN. Although the on-treatment cell-cycle effects were not affected by the TP53 status, a marked proapoptotic response to therapy was observed exclusively in wild-type TP53 colorectal cancer models. We further interrogated two independent panels of KRAS/BRAF- and PIK3CA/PTEN-altered cell line- and patient-derived tumor xenografts for the antitumor response toward this combination of agents. A combination response that resulted in substantial antitumor activity was exclusively observed among the wild-type TP53 models (two out of five, 40%), but there was no such response across the eight mutant TP53 models (0%). Interestingly, within a cohort of 14 patients with colorectal cancer treated with these agents for their metastatic disease, two patients with long-lasting responses (32 weeks) had TP53 wild-type tumors.

CONCLUSIONS

Our data support that, in wild-type TP53 colorectal cancer cells with ERK and PI3K pathway alterations, MEK blockade results in potent p21 induction, preventing apoptosis to occur. In turn, mTORC1/2 inhibition blocks MEK inhibitor-mediated p21 induction, unleashing apoptosis. Clin Cancer Res; 21(24); 5499-510. ©2015 AACR.

A mouse model uncovers LKB1 as an UVB-induced DNA damage sensor mediating CDKN1A (p21WAF1/CIP1) degradation

Exposure to ultraviolet (UV) radiation from sunlight accounts for 90% of the symptoms of premature skin aging and skin cancer. The tumor suppressor serine-threonine kinase LKB1 is mutated in Peutz-Jeghers syndrome and in a spectrum of epithelial cancers whose etiology suggests a cooperation with environmental insults. Here we analyzed the role of LKB1 in a UV-dependent mouse skin cancer model and show that LKB1 haploinsufficiency is enough to impede UVB-induced DNA damage repair, contributing to tumor development driven by aberrant growth factor signaling. We demonstrate that LKB1 and its downstream kinase NUAK1 bind to CDKN1A. In response to UVB irradiation, LKB1 together with NUAK1 phosphorylates CDKN1A regulating the DNA damage response. Upon UVB treatment, LKB1 or NUAK1 deficiency results in CDKN1A accumulation, impaired DNA repair and resistance to apoptosis. Importantly, analysis of human tumor samples suggests that LKB1 mutational status could be a prognostic risk factor for UV-induced skin cancer. Altogether, our results identify LKB1 as a DNA damage sensor protein regulating skin UV-induced DNA damage response.

Environmental insults are directly involved in cancer development. In particular, Ultraviolet (UV) radiation has been associated to the acquisition of different types skin cancer and premature skin aging. UV radiation causes modifications in the genetic material of cells (DNA) that if not repaired properly will lead to a mutated DNA (mutated genes) which might trigger the development of cancer. Understanding the molecular basis of the UV-induced DNA damage response is important to elucidate the mechanisms of skin homeostasis and tumorigenesis. Here we provide a UVB-induced skin cancer animal model showing that LKB1 tumor suppressor is also a DNA damage sensor. Importantly, the data suggest that reduced amounts of LKB1 protein in skin could be a risk factor for UV-induced skin carcinogenesis in humans.

Abstract C114: Clinical response to a lapatinib-based therapy of a Li-Fraumeni Syndrome patient with a novel HER2-V659E mutation

Genomic characterization of recurrent breast and lung tumors developed over the course of 10 years in a 29-year-old patient with a germline p53 mutation (Li-Fraumeni Syndrome) identified oncogenic alterations in the HER2 and EGFR genes across all tumors, including HER2 amplifications, an EGFR-exon 20 insertion, and the first-in-human HER2-V659E mutation showing a phenotypic convergent evolution towards HER2 and EGFR alterations. Following the identification of HER2-activating events in the most recent lung carcinoma and in circulating tumor cells, we treated the reminiscent metastatic lesions with a lapatinib-based therapy. A clinical response both symptomatic and radiologic was achieved. HER2-V659E sensitivity to lapatinib was confirmed in the laboratory.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C114.

Citation Format: Violeta Serra, Ana Vivancos, Xose Puente, Enriqueta Felip, Daniel Silberschmidt, Ginevra Caratù, Josep-Lluis Parra, Leticia De Mattos-Arruda, Judit Grueso, Javier Hernández-Losa, Joaquín Arribas, Ludmila Prudkin, Paolo Nuciforo, Maurizio Scaltriti, Joan Seoane, José Baselga. Clinical response to a lapatinib-based therapy of a Li-Fraumeni Syndrome patient with a novel HER2-V659E mutation. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C114.

Clinical response to a lapatinib-based therapy for a Li-Fraumeni syndrome patient with a novel HER2V659E mutation

Genomic characterization of recurrent breast and lung tumors developed over the course of 10 years in a 29-year-old patient with a germline TP53 mutation (Li-Fraumeni Syndrome) identified oncogenic alterations in the HER2 and EGFR genes across all tumors, including HER2 amplifications, an EGFR-exon 20 insertion, and the first-in-humans HER2V659E mutation showing a phenotypic convergent evolution toward HER2 and EGFR alterations. Following the identification of HER2-activating events in the most recent lung carcinoma and in circulating tumor cells, we treated the reminiscent metastatic lesions with a lapatinib-based therapy. A symptomatic and radiologic clinical response was achieved. HER2V659E sensitivity to lapatinib was confirmed in the laboratory.

SIGNIFICANCE

The precise knowledge of the genomic alterations present in tumors is critical to selecting the optimal treatment for each patient. Here, we report the molecular characterization and clinical response to a lapatinib-based therapy for the tumors of a Li-Fraumeni patient showing prevalence of HER2 and EGFR genomic alterations.

Abstract LB-96: Sensitivity to combined MEK and mTORC1/2 inhibition in colorectal cancer is dictated by p53 mutational status

Activating mutations in RAS and PI3K pathways confer resistance to currently used anti-EGFR-based therapies in colorectal cancer (CRC). Although dual inhibition of MEK and PI3K/Akt has proven some efficacy in CRC preclinical models with aberrations in both pathways, little is known about other possible alterations that can limit the efficacy of this combination and preclude patient selection. Here, we explored whether p53 mutations influence the response to combined MEK and PI3K pathway inhibition by analyzing the antiproliferative activity of the investigational dual mTORC1/2 inhibitor MLN0128, and the MEK inhibitor PD0325901, in three p53 wild-type and three p53 mutated CRC cell lines with concomitant KRAS/BRAF and PIK3CA mutations. Expectedly, PD0325901 and MLN0128 inhibited ERK and mTOR signaling, respectively, across all cell-lines. However, the treatment combination selectively enhanced apoptosis only in p53 wild-type cell lines. Overexpression of mutant p53 in p53 wild-type CRC cells prevented the proapoptotic effects of combined PD0325901 and MLN0128, underscoring the causative role of mutant p53 in limiting the sensitivity to this pharmacological approach. Similar results were observed in vivo, where the inhibition of MEK and mTORC1/2 reduced tumor growth in a higher extent than single agents in p53 wild-type xenograft models, but not in p53 mutant ones. p53 can inhibit cell apoptosis and cycle progression partly by increasing the expression of the cyclin-dependent kinase inhibitor p21, which, in turn, is regulated by MEK-ERK-cMyc pathway. Accordingly, we observed a decrease of cMyc and an increase of p21 levels following MEK inhibition, which could exert an anti-apoptotic function in wild-type p53 CRC. As expected, the combined treatment with the mTORC1/2 inhibitor prevented the PD0325901-induced p21 expression and resulted in enhanced apoptosis. Knockdown of p21 in p53 wild-type cells also sensitized CRC cells to MEK inhibitor-induced apoptosis, confirming the antiapoptotic role of p21 upon PD0325901 treatment and supporting the hypothesis that p21-downregulation mediated by MLN0128 is needed to achieve cell death following dual MEK and mTOR inhibition. In summary, our data suggest that the presence of wild-type p53 is a determinant of sensitivity to the combined suppression of MEK and PI3K-pathways in CRC.

Citation Format: Celina García-García, Martín A. Rivas, Yasir H. Ibrahim, María Teresa Calvo, Judit Grueso, Pilar Antón, Claudia Aura, Katti Jessen, Héctor Palmer, Josep Tabernero, Maurizio Scaltriti, José Baselga, Violeta Serra. Sensitivity to combined MEK and mTORC1/2 inhibition in colorectal cancer is dictated by p53 mutational status. . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-96. doi:10.1158/1538-7445.AM2013-LB-96

PI3K inhibition impairs BRCA1/2 expression and sensitizes BRCA-proficient triple-negative breast cancer to PARP inhibition

PARP inhibitors are active in tumors with defects in DNA homologous recombination (HR) due to BRCA1/2 mutations. The phosphoinositide 3-kinase (PI3K) signaling pathway preserves HR steady state. We hypothesized that in BRCA-proficient triple-negative breast cancer (TNBC), PI3K inhibition would result in HR impairment and subsequent sensitization to PARP inhibitors. We show in TNBC cells that PI3K inhibition leads to DNA damage, downregulation of BRCA1/2, gain in poly-ADP-ribosylation, and subsequent sensitization to PARP inhibition. In TNBC patient-derived primary tumor xenografts, dual PI3K and PARP inhibition with BKM120 and olaparib reduced the growth of tumors displaying BRCA1/2 downregulation following PI3K inhibition. PI3K-mediated BRCA downregulation was accompanied by extracellular signal-regulated kinase (ERK) phosphorylation. Overexpression of an active form of MEK1 resulted in ERK activation and downregulation of BRCA1, whereas the MEK inhibitor AZD6244 increased BRCA1/2 expression and reversed the effects of MEK1. We subsequently identified that the ETS1 transcription factor was involved in the ERK-dependent BRCA1/2 downregulation and that knockdown of ETS1 led to increased BRCA1/2 expression, limiting the sensitivity to combined BKM120 and olaparib in 3-dimensional culture.

SIGNIFICANCE

Treatment options are limited for patients with TNBCs. PARP inhibitors have clinical activity restricted to a small subgroup of patients with BRCA mutations. Here, we show that PI3K blockade results in HR impairment and sensitization to PARP inhibition in TNBCs without BRCA mutations, providing a rationale to combine PI3K and PARP inhibitors in this indication. Our findings could greatly expand the number of patients with breast cancer that would benefit from therapy with PARP inhibitors. On the basis of our findings, a clinical trial with BKM120 and olaparib is being initiated in patients with TNBCs.

Abstract 1811: Antitumor activity of lapatinib in combination with the dual mTORC1/2 inhibitor INK-128 in breast tumors resistant to anti-HER2 therapy

Purpose: The PI3K/Akt/mTOR pathway is an attractive target in HER2 positive breast cancer refractory to anti-HER2 therapy. The hypothesis is that suppression of this pathway results in sensitization to anti-HER2 agents. However, this combinatorial strategy has not been comprehensively tested in models of trastuzumab and lapatinib resistance. Experimental Design: We analyzed in vitro cell viability and induction of apoptosis in five different cell lines resistant to trastuzumab and lapatinib. Inhibition of HER2/HER3 phosphorylation, PI3K/Akt/mTOR and ERK signaling pathways was evaluated by western blot. Tumor growth inhibition following treatment with lapatinib, INK-128 or the combination of both agents was evaluated in three different animal models: two cell-based xenograft models refractory to both trastuzumab and lapatinib and a xenograft derived from a patient who relapsed to trastuzumab-based therapy. Results: The addition of lapatinib to INK-128 prevented both HER2 and HER3 phosphorylation induced by INK-128, resulting in inhibition of both PI3K/Akt/mTOR and ERK pathways. This dual blockade synergistically enhanced cell death in five different HER2 positive cell lines resistant to trastuzumab and lapatinib. In vivo, both cell line-based and patient-derived xenografts showed exquisite sensitivity to the antitumor activity of the combination of lapatinib and INK-128, causing durable tumor shrinkage in the absence of any sign of toxicity. Conclusions: The simultaneous blockade of PI3K/Akt/mTOR and ERK pathways achieved by combining lapatinib with INK-128 acts synergistically in inducing cell death and tumor regression in breast cancer refractory to anti-HER2 therapy.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1811. doi:1538-7445.AM2012-1811

Dual mTORC1/2 and HER2 blockade results in antitumor activity in preclinical models of breast cancer resistant to anti-HER2 therapy

PURPOSE

The PI3K/Akt/mTOR pathway is an attractive target in HER2-positive breast cancer that is refractory to anti-HER2 therapy. The hypothesis is that the suppression of this pathway results in sensitization to anti-HER2 agents. However, this combinatorial strategy has not been comprehensively tested in models of trastuzumab and lapatinib resistance.

EXPERIMENTAL DESIGN

We analyzed in vitro cell viability and induction of apoptosis in five different cell lines resistant to trastuzumab and lapatinib. Inhibition of HER2/HER3 phosphorylation, PI3K/Akt/mTOR, and extracellular signal-regulated kinase (ERK) signaling pathways was evaluated by Western blotting. Tumor growth inhibition after treatment with lapatinib, INK-128, or the combination of both agents was evaluated in three different animal models: two cell-based xenograft models refractory to both trastuzumab and lapatinib and a xenograft derived from a patient who relapsed on trastuzumab-based therapy.

RESULTS

The addition of lapatinib to INK-128 prevented both HER2 and HER3 phosphorylation induced by INK-128, resulting in inhibition of both PI3K/Akt/mTOR and ERK pathways. This dual blockade produced synergistic induction of cell death in five different HER2-positive cell lines resistant to trastuzumab and lapatinib. In vivo, both cell line-based and patient-derived xenografts showed exquisite sensitivity to the antitumor activity of the combination of lapatinib and INK-128, which resulted in durable tumor shrinkage and exhibited no signs of toxicity in these models.

CONCLUSIONS

The simultaneous blockade of both PI3K/Akt/mTOR and ERK pathways obtained by combining lapatinib with INK-128 acts synergistically in inducing cell death and tumor regression in breast cancer models refractory to anti-HER2 therapy.

Methylthioadenosine (MTA) inhibits melanoma cell proliferation and in vivo tumor growth

Background

Melanoma is the most deadly form of skin cancer without effective treatment. Methylthioadenosine (MTA) is a naturally occurring nucleoside with differential effects on normal and transformed cells. MTA has been widely demonstrated to promote anti-proliferative and pro-apoptotic responses in different cell types. In this study we have assessed the therapeutic potential of MTA in melanoma treatment.

Methods

To investigate the therapeutic potential of MTA we performed in vitro proliferation and viability assays using six different mouse and human melanoma cell lines wild type for RAS and BRAF or harboring different mutations in RAS pathway. We also have tested its therapeutic capabilities in vivo in a xenograft mouse melanoma model and using variety of molecular techniques and tissue culture we investigated its anti-proliferative and pro-apoptotic properties.

Results

In vitro experiments showed that MTA treatment inhibited melanoma cell proliferation and viability in a dose dependent manner, where BRAF mutant melanoma cell lines appear to be more sensitive. Importantly, MTA was effective inhibiting in vivo tumor growth. The molecular analysis of tumor samples and in vitro experiments indicated that MTA induces cytostatic rather than pro-apoptotic effects inhibiting the phosphorylation of Akt and S6 ribosomal protein and inducing the down-regulation of cyclin D1.

Conclusions

MTA inhibits melanoma cell proliferation and in vivo tumor growth particularly in BRAF mutant melanoma cells. These data reveal a naturally occurring drug potentially useful for melanoma treatment.

The dual PI3K/mTOR inhibitor PI-103 promotes immunosuppression, in vivo tumor growth and increases survival of sorafenib-treated melanoma cells

Melanoma is the most lethal human skin cancer. If metastatic, it becomes very aggressive and resistant to standard modalities of anticancer treatment. During the last 10 years, several therapeutic strategies have been tested including the use of single and combined small drugs. Experimental results indicate that RAS and PI3K pathways are important for the development and maintenance of melanoma. In this study, we assessed the in vitro and in vivo inhibition potential of PI-103, a PI3K (p110alpha)/mTOR inhibitor and sorafenib, a BRAF inhibitor, as single agents and in combination in primary melanoma cell lines. Although PI-103 and sorafenib inhibited melanoma in vitro cell proliferation and viability, the inhibition of RAS pathway appeared to be more effective. The combination of the two agents in in vitro showed a synergistic effect inhibiting RAS and PI3K pathways in a cell line dependent manner. However, no cooperative effect was observed in blocking in vivo tumor growth in immunocompetent mice. In contrary to the expected, the data indicate that PI-103 induced immunosuppression promoting in vivo tumor growth and inhibiting apoptosis. Furthermore, in vitro studies examining the effects of the PI3K/mTOR inhibitor in tumor derived cell lines indicated that PI-103 induced the anti-apoptotic BH3 family proteins Mcl1, Bcl2 and Bcl(xL) favoring, the in vitro survival of sorafenib treated melanoma cells. These data certainly makes an argument for investigating unexpected effects of rational drug combinations on immunocompetent animal models prior to conducting clinical studies.

Phosphorylation regulates the subcellular location and activity of the snail transcriptional repressor

The Snail gene product is a transcriptional repressor of E-cadherin expression and an inducer of the epithelial-to-mesenchymal transition in several epithelial tumor cell lines. This report presents data indicating that Snail function is controlled by its intracellular location. The cytosolic distribution of Snail depended on export from the nucleus by a CRM1-dependent mechanism, and a nuclear export sequence (NES) was located in the regulatory domain of this protein. Export of Snail was controlled by phosphorylation of a Ser-rich sequence adjacent to this NES. Modification of this sequence released the restriction created by the zinc finger domain and allowed nuclear export of the protein. The phosphorylation and subcellular distribution of Snail are controlled by cell attachment to the extracellular matrix. Suspended cells presented higher levels of phosphorylated Snail and an augmented extranuclear localization with respect to cells attached to the plate. These findings show the existence in tumor cells of an effective and fine-tuning nontranscriptional mechanism of regulation of Snail activity dependent on the extracellular environment.

[Atrial septostomy with a balloon catheter under echocardiographic control. Our experience]

INTRODUCTION

We report our experience in balloon atrial septostomy using two-dimensional echocardiography as control for the catheter placement and performance of the procedure instead of traditional fluoroscopic control.

PATIENTS AND METHODS

We carried out atrial septostomy in 12 consecutive neonates with age between 1 and 18 days (mean = 3.6 +/- 5 days) diagnosed as d-transposition of the great arteries (10 cases) and pulmonary atresia with intact ventricular septum (2 cases). The procedures were performed in the catheterization laboratory in 7 cases. In the five remaining cases it was done in the neonatal intensive care unit. We emphasise the good visualization of the full balloon within the left atrium and its relationship with the mitral valve and the pulmonary veins, as well as, the problems found in case number 2 for initial placement of the catheter in the left atrium.

RESULTS

An adequate atrial septal defect was achieved in all patients with diameter between 6 and 12 mm (mean = 8.6 +/- 2 mm). There were no complications using this technique, except a supraventricular tachycardia which stopped spontaneously. The evolution of the patients have been satisfactory, and 11 of them underwent surgery. Patient number 2 died suddenly on the third day after atrial septostomy.

CONCLUSIONS

We conclude that atrial septostomy with balloon catheter can be carried out safely, under echocardiographic control in the intensive care unit. Above all, critical patients should not be removed from the unit because they are high risk patients.

[Double-outlet right ventricle with mitral atresia. Study of 9 cases]

Double-outlet right ventricle with mitral atresia is an uncommon anomaly with a few cases reported in the literature. We present 9 cases of this malformation that have been diagnosed by two-dimensional echocardiography (7 cases), cardiac catheterization (9 cases) and anatomical study (2 cases). We classify them into two groups according to whether or not they have associated pulmonary stenosis. The dominant symptoms were cyanosis and hypoxemia in the first group and cardiac insufficiency signs in the other. The left ventricle was hypoplastic in eight and normal in the one with tricuspid overriding. Six of the cases had ventricular septal defect. The great arteries were in normal relationship in 4 cases, with D-malposition in 3 cases and side-by-side in 2 cases. Rashkind atrial septotomy was performed in 5 patients, but was effective only in two. Palliative surgical treatment was performed on six of them. The actual survival rate is 44%.