Amelia D'Alessio

The RAS/RAF/MEK/ERK and the PI3K/AKT signalling pathways: role in cancer pathogenesis and implications for therapeutic approaches

Introduction: The RAS/RAF/MAP kinase–ERK kinase (MEK)/extracellular-signal-regulated kinase (ERK) (MAPK) and the PI3K/AKT/mammalian target of rapamycin (mTOR) (PI3K) pathways are frequently deregulated in human cancer as a result of genetic alterations in their components or upstream activation of cell-surface receptors. These signalling cascades are regulated by complex feedback and cross-talk mechanisms. Areas covered: In this review the key components of the MAPK and AKT pathways and their molecular alterations are described. The complex interactions between these signalling cascades are also analysed. Expert opinion: The observation that the MAPK and the PI3K pathways are often deregulated in human cancer makes the components of these signalling cascades interesting targets for therapeutic intervention. Recently, the presence of compensatory loops that activate one pathway following the blockade of the other signalling cascade has been demonstrated. Therefore, the blockade of both pathways with combinations of signalling inhibitors might result in a more efficient anti-tumor effect as compared with a single agent. In addition, the MAPK and PI3K pathways are activated by mutations that coexist or can be mutually exclusive. In this regard, a large-scale characterization of the cancer genome might offer personalized cancer genomic information, which may improve the anti-tumor efficacy of signalling inhibitors.

Role of the EGFR ligand/receptor system in the secretion of angiogenic factors in mesenchymal stem cells.

Increasing evidence suggests that bone marrow‐derived mesenchymal stem cells (MSCs) are recruited into the stroma of developing tumors where they contribute to cancer progression. MSCs produce different growth factors that sustain tumor‐associated neo‐angiogenesis. Since the majority of carcinomas secrete ligands of the epidermal growth factor receptor (EGFR), we assessed the role of EGFR signaling in regulating the release of angiogenic factors in MSCs. Treatment of human primary MSCs and of the human osteoblastic cell line hFOB with transforming growth factor α (TGF‐α), one of the main ligands of the EGFR, significantly induced activation of this receptor and of different intracellular signaling proteins, including the PI3K/AKT and the MEK/MAPK pathways. TGF‐α induced a significant increase in the levels of secretion of vascular endothelial growth factor in both MSCs and hFOB. Conditioned medium from TGF‐α treated MSCs showed an higher in vivo angiogenic effect as compared with medium from untreated cells. Treatment of MSCs with TGF‐α also produced a significant increase in the secretion of other angiogenic growth factors such as angiopoietin‐2, granulocyte‐colony stimulating factor, hepatocyte growth factor, interleukin (IL)‐6, IL‐8, and platelet‐derived growth factor‐BB. Using selective MEK and PI3K inhibitors, we found that both MEK/MAPK and the PI3K/AKT signaling pathways mediate the ability of TGF‐α to induce secretion of angiogenic factors in MSCs. Finally, stimulation with TGF‐α increased the ability of MSCs to induce migration of MCF‐7 breast cancer cells. These data suggest that EGFR signaling regulates the ability of MSCs to sustain cancer progression through the release of growth factors that promote neo‐angiogenesis and tumor cell migration. J. Cell. Physiol. 226: 2131–2138, 2011.

Src and CXCR4 are involved in the invasiveness of breast cancer cells with acquired resistance to lapatinib

Lapatinib is a dual EGFR and ErbB-2 tyrosine kinase inhibitor that has significantly improved the clinical outcome of ErbB-2-overexpressing breast cancer patients. However, patients inexorably develop mechanisms of resistance that limit the efficacy of the drug. In order to identify potential targets for therapeutic intervention in lapatinib-resistant patients, we isolated, from ErbB-2-overexpressing SK-Br-3 breast cancer cells, the SK-Br-3 Lap-R-resistant subclone, which is able to routinely grow in 1 µM lapatinib. Resistant cells have a more aggressive phenotype compared with parental cells, as they show a higher ability to invade through a matrigel-coated membrane. Lapatinib-resistant cells have an increased Src kinase activity and persistent levels of activation of ERK1/2 and AKT compared with parental cells. Treatment with the Src inhibitor saracatinib in combination with lapatinib reduces AKT and ERK1/2 phosphorylation and restores the sensitivity of resistant cells to lapatinib. SK-Br-3 Lap-R cells also show levels of expression of CXCR4 that are higher compared with parental cells and are not affected by Src inhibition. Treatment with saracatinib or a specific CXCR4 antibody reduces the invasive ability of SK-Br-3 Lap-R cells, with the two drugs showing cooperative effects. Finally, blockade of Src signaling significantly increases TRAIL-induced cell death in SK-Br-3 Lap-R cells. Taken together, our results demonstrate that breast cancer cells with acquired resistance to lapatinib have a more aggressive phenotype compared with their parental counterpart, and that Src signaling and CXCR4 play an important role in this phenomenon, thus representing potential targets for therapeutic intervention in lapatinib-resistant breast cancer patients.

Prognostic Applications of Gene Expression Signatures in Breast Cancer

Analysis by DNA microarrays has led to the identification of molecular subtypes of breast carcinomas that show a distinct expression profile. Several studies have demonstrated that this ‘intrinsic subtype’ classification has a strong prognostic value. In addition, gene expression profiling techniques have been used to identify gene signatures that could be associated with the outcome of breast cancer patients. Several different genomic tests have been shown to better define the prognosis of early-stage breast cancer patients as compared with conventional clinical and pathological characteristics of the tumors, and some assays are already commercially available. However, it must be emphasized that the prognostic power of these genetic classifiers has not been confirmed yet in prospective trials. Genetic signatures that might predict the activity of specific chemotherapy agents have also been developed by using gene expression profiling techniques. The same approach has been used to identify gene signatures associated with the activation of oncogenic pathways that might represent targets for molecular therapy of breast cancer. By using these approaches, gene expression techniques might significantly improve our ability to predict the risk of recurrence and to tailor the treatment for each individual breast cancer patient.

Quercetin-3-methyl ether inhibits lapatinib-sensitive and -resistant breast cancer cell growth by inducing G2/M arrest and apoptosis

Lapatinib, an oral, small‐molecule, reversible inhibitor of both EGFR and HER2, is highly active in HER2 positive breast cancer as a single agent and in combination with other therapeutics. However, resistance against lapatinib is an unresolved problem in clinical oncology. Recently, interest in the use of natural compounds to prevent or treat cancers has gained increasing interest because of presumed low toxicity. Quercetin‐3‐methyl ether, a naturally occurring compound present in various plants, has potent anticancer activity. Here, we found that quercetin‐3‐methyl ether caused a significant growth inhibition of lapatinib‐sensitive and ‐resistant breast cancer cells. Western blot data showed that quercetin‐3‐methyl ether had no effect on Akt or ERKs signaling in resistant cells. However, quercetin‐3‐methyl ether caused a pronounced G2/M block mainly through the Chk1‐Cdc25c‐cyclin B1/Cdk1 pathway in lapatinib‐sensitive and ‐resistant cells. In contrast, lapatinib produced an accumulation of cells in the G1 phase mediated through cyclin D1, but only in lapatinib‐sensitive cells. Moreover, quercetin‐3‐methyl ether induced significant apoptosis, accompanied with increased levels of cleaved caspase 3, caspase 7, and poly(ADP‐ribose) polymerase (PARP) in both cell lines. Overall, these results suggested that quercetin‐3‐methyl ether might be a novel and promising therapeutic agent in lapatinib‐sensitive or ‐resistant breast cancer patients.

EGFR and MEK Blockade in Triple Negative Breast Cancer Cells.

Although evidence suggests that the RAF/MEK/ERK pathway plays an important role in triple negative breast cancer (TNBC), resistance to MEK inhibitors has been observed in TNBC cells. Different mechanisms have been hypothesized to be involved in this phenomenon, including receptor tyrosine kinase‐dependent activation of the PI3K/AKT pathway. In this study, we analyzed the effects of the MEK1/2 inhibitor selumetinib in combination with the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor gefitinib in a panel of TNBC cell lines that showed different levels of sensitivity to single‐agent selumetinib: SUM‐149 and MDA‐MB‐231 cells resulted to be sensitive, whereas SUM‐159, MDA‐MB‐468 and HCC70 cells were relatively resistant to the drug. Treatment of TNBC cells with selumetinib produced an increase of the phosphorylation of the EGFR both in selumetinib‐sensitive SUM‐149, MDA‐MB‐231 and in selumetinib‐resistant MDA‐MB‐468 TNBC cells. The combination of selumetinib and gefitinib resulted in a synergistic growth inhibitory effect in all the TNBC cell lines, although the IC50 was not reached in SUM‐159 and MDA‐MB‐468 cells. This effect was associated with an almost complete suppression of ERK1/2 activation and a reduction of selumetinib‐induced AKT phosphorylation. In addition, in selumetinib‐sensitive TNBC cells the combination of selumetinib and gefitinib induced a significant G0/G1 cell cycle arrest and apoptosis. Taken together, our data demonstrated that blockade of the EGFR might efficiently increase the antitumor activity of selumetinib in a subgroup of TNBC and that this phenomenon might be related to the effects of such combination on both ERK1/2 and AKT activation. J. Cell. Biochem. 116: 2778–2785, 2015.

Pharmacokinetic evaluation of zoledronic acid

Introduction: Increased bone resorption is associated with several diseases, including osteoporosis, bone metastases and Pagets disease of bone. Zoledronic acid (ZA) is the most potent of the clinically available bisphosphonates. In addition to its antiresorptive activity, there has been increasing evidence to suggest that it also has anticancer properties. Areas covered: This article is complied through PubMed and Medline databases searches on ZA. In this review, the authors summarize the current knowledge (up to December 2010) on the pharmacodynamic and pharmacokinetic properties of ZA. Expert opinion: ZA is a well-tolerated and effective drug in the management of metabolic as well as cancer-related bone disease. Clinical benefits in cancer patients include improvement in bone pain, reduction in skeletal events and delay of time to first skeletal event. However, novel indications for this drug are emerging from clinical studies in early breast cancer. Recent findings suggest that the addition of ZA to endocrine therapy can significantly prevent bone loss in premenopausal patients. Increasing evidence also indicates a potential anticancer activity of ZA, although this property needs to be further explored.

Vascular Endothelial Growth Factor A Regulates the Secretion of Different Angiogenic Factors in Lung Cancer Cells.

Vascular endothelial growth factor A (VEGFA) is one of the main mediators of angiogenesis in non‐small cell lung cancer (NSCLC). Recently, it has been described an autocrine feed‐forward loop in NSCLC cells in which tumor‐derived VEGFA promoted the secretion of VEGFA itself, amplifying the proangiogenic signal. In order to investigate the role of VEGFA in lung cancer progression, we assessed the effects of recombinant VEGFA on proliferation, migration, and secretion of other angiogenic factors in A549, H1975, and HCC827 NSCLC cell lines. We found that VEGFA did not affect NSCLC cell proliferation and migration. On the other hand, we demonstrated that VEGFA not only produced a strong and persistent increase of VEGFA itself but also significantly induced the secretion of a variety of angiogenic factors, including follistatin (FST), hepatocyte growth factor (HGF), angiopoietin‐2 (ANGPT2), granulocyte‐colony stimulating factor (G‐CSF), interleukin (IL)‐8, leptin (LEP), platelet/endothelial cell adhesion molecule 1 (PECAM‐1), and platelet‐derived growth factor bb (PDGF‐BB). PI3K/AKT, RAS/ERK, and STAT3 signalling pathways were found to mediate the effects of VEGFA in NSCLC cell lines. We also observed that VEGFA regulation mainly occurred at post‐transcriptional level and that NSCLC cells expressed different isoforms of VEGFA. Collectively, our data suggested that VEGFA contributes to lung cancer progression by inducing a network of angiogenic factors, which might offer potential for therapeutic intervention. J. Cell. Physiol. 231: 1514–1521, 2016.

Pharmacokinetic evaluation of capecitabine in breast cancer

Introduction: Capecitabine, an oral prodrug of 5-fluorouracil (5-FU), is adsorbed in its intact form through the intestine and metabolized to 5-FU in tumour cells. In metastatic breast cancer (MBC), capecitabine is an effective and well-tolerated therapeutic option both in monotherapy and in combination with chemotherapeutic or molecular-targeted agents. Areas covered: We summarized data on pharmacokinetics and pharmacodynamics of capecitabine. We also produced a general review of the most relevant clinical studies of capecitabine in MBC. A literature search was performed using PubMed database including selected articles published in English language up to October 2012. Expert opinion: The unique pharmacodynamic/pharmacokinetic features represent the bases of the reduced toxicity and the activity of capecitabine in several tumours. Although during the past 10 years there has been an increasing use of this drug in MBC both as single agent and in combination, encouraging results of well tolerated and active combinations with novel agents will lead to a more extensive and protracted use of capecitabine. In view of this, some aspects should be further clarified such as the optimal starting dose and the introduction of alternative schedules of treatment.

Effects of the combined blockade of EGFR and ErbB-2 on signal transduction and regulation of cell cycle regulatory proteins in breast cancer cells.

CTRC-AACR San Antonio Breast Cancer Symposium: 2008 Abstracts Abstract #2130 Co-expression of EGFR and ErbB-2 occurs in a subset of primary breast carcinoma, and it is associated with worse prognosis. We previously demonstrated that treatment of breast cancer cells that express both receptors with a combination of the EGFR tyrosine kinase inhibitor gefitinib (G) and the anti-ErbB-2 monoclonal antibody herceptin (H) results in a synergistic anti-tumor effect. Such combination failed to show significant activity in a phase I/II clinical trial. However, patients enrolled in this trial were not selected for expression of EGFR. We explored the molecular mechanisms involved in the synergism of G and H in breast cancer cells. Treatment of both SK-BR-3 and BT-474 cells with a combination of G+H produced a more significant reduction of AKT and p42/p44-MAPK (MAPK) activation as compared with treatment with a single agent. The combination also produced a more prolonged blockade of both signalling pathways. In agreement with these findings, treatment with G+H induced a more pronounced accumulation of cells in the G0/G1 phase of the cell cycle as compared with treatment with a single drug. A sub-G0/G1 peak, suggestive of apoptosis, was evident in cells treated with the combination but not with G or H. The combination of G+H produced a more significant increase in the levels of p27kip1 and of hypophosphorylated forms of pRb2, and a more significant decrease in the levels of Cyclin D1 and survivin as compared with a single agent. Analysis of p27kip1 protein stability, in presence of the protein synthesis inhibitor cycloheximide, revealed that both G and the combination of G+H significantly increased the stability of p27kip1, with the combination showing higher effects. Furthermore, breast cancer cells treated with the combination expressed higher levels of p27kip1 mRNA as compared with cells treated with a single drug. The combination also induced a significant increase in the nuclear levels of the FKHRL-1 transcription factor that was not observed in cells treated with G or H alone. Treatment of breast cancer cells with the dual EGFR/ErbB-2 inhibitor lapatinib produced an increase in the levels of p27kip1 and of hypophosphorylated pRb2, and a decrease in the levels of Cyclin D1 and survivin comparable to that observed following treatment with the combination of G+H. In addition, an increase in p27kip1 mRNA and in the nuclear levels of FKHRL-1 was induced in breast cancer cells by treatment with lapatinib. These findings suggest that the synergistic anti-tumor effects deriving from EGFR and ErbB-2 blockade are mediated by significant alterations in the expression of cell cycle regulatory proteins, including transcriptional and post-transcriptional regulation of p27kip1 expression. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2130.