Gilteritinib as treatment for extra-medullary relapse of FLT3-ITD acute myeloid leukemia FLT3-ITD, after allogeneic haematopoietic stem cell transplantation

Case of a patient with acute myeloid leukemia (AML) positive for mutations in both genes NPM1 and FLT3-ITD who underwent two allogeneic haematopoietic stem cell transplants (HSCT); the second allograft one was followed by extramedullary relapse (granulocytic sarcoma of right breast), with blast cells positive for FLT3-ITDmutation.  Treatment with Gilteritinib, a second generation selective oral type I FLT3 inhibitor, was started after the second HSCT with complete regression of breast granulocytic sarcoma in absence of hematological and extra hematologic toxicity. We conclude that Gilteritinib can represent an effective therapy for extra hematologic relapse, with acceptable toxicity and outpatient management.

Palbociclib as single agent or in combination with the endocrine therapy received before disease progression for estrogen receptor-positive, HER2-negative metastatic breast cancer: TREnd trial

Background

The activity of palbociclib as a single agent in advanced breast cancer has not been extensively studied, with the only available clinical data limited to heavily pretreated patients. Preclinical data suggests palbociclib may partially reverse endocrine resistance, though this hypothesis has not been evaluated in previous clinical studies. This phase II, open-label, multicenter study examined the activity of palbociclib monotherapy, as well as palbociclib given in combination with the same endocrine therapy (ET) that was received prior to disease progression, in postmenopausal women with moderately pretreated, estrogen receptor-positive, HER2 negative advanced breast cancer.

Patients and methods

Eligible women with advanced disease which had progressed on one or two prior ETs were randomized 1 : 1 to receive either palbociclib alone, or palbociclib in combination with the ET as previously received. Primary end point was clinical benefit rate (CBR); secondary end points included progression-free survival (PFS).

Results

Between October 2012 and July 2016, a total of 115 patients were randomized. The CBR was 54% [95% confidence interval (CI): 41.5-63.7] for combination therapy, and 60% (95% CI: 47.8-72.9) for monotherapy. Median PFS was 10.8 months (95% CI: 5.6-12.7) for combination therapy, and 6.5 months (95% CI: 5.4-8.5) for monotherapy [hazard ratio (HR) 0.69; 95% CI: 0.4-1.1, exploratory P-value = 0.12]. Exploratory analyses revealed the PFS advantage for combination therapy was seen in the subgroup of patients who received prior ET for >6 months (HR 0.53; 95% CI: 0.3-0.9, exploratory P-value = 0.02), but not in those who received prior ET for ≤6 months.

Conclusion

Palbociclib has clinical activity as a single agent in women with moderately pretreated, oestrogen receptor-positive, HER2-negative advanced breast cancer. Palbociclib may have potential to reverse endocrine resistance in patients with a history of previous durable response to ET.

Clinical trial information

NCT02549430.

Abstract P6-09-02: Effects of palbociclib on thymidine kinase-1 (TK1) in hormone receptor positive (HR+) breast cancer cell lines

Introduction: TK1 plays a crucial role in DNA synthesis and is a well-established marker of cell proliferation. We and others have previously described the potential role of TK1 activity (TKa) as predictive biomarker of response to endocrine therapy in HR+/HER2 negative metastatic breast cancer patients. TK1 synthesis is regulated by the E2F pathway, the target pathway of CDK4/6 inhibitors, and TKa has recently been reported as a potential circulating pharmacodynamic marker of CDK4/6 inhibition in breast cancer. However, modulations of TK1 levels and activity during palbociclib treatment and in the development of treatment resistance are unknown. Here, we report how TK1 expression and TKa are modulated in response to palbociclib in a panel of HR+ breast cancer cell lines: both palbociclib-sensitive (PDS) and with acquired resistance to (PDR).

Material and methods: We used a panel of 7 PDR HR+ breast cancer models previously developed in our lab via chronic exposure of parental cells (MCF7, T47D, ZR75-1, BT474, MDAMB361 and two MCF7 endocrine resistant derivatives) to escalating doses of palbociclib, from a Starting Treatment Concentration (STC) of 50 nM or 350 nM according to the cell line, up to 1 μM. We analyzed gene expression profiles of PDS cells treated with drug vehicle (DMSO) as a control or palbociclib at STC for 3 days, and PDR cells grown with palbociclib 1 μM. Cell proliferation was assessed by methylene blue assay in MCF7 and BT474 PDS and PDR treated for 3, 6 and 9 days with DMSO, palbociclib STC and 1 μM. In parallel, TKa was measured in cell lysates at 3 days of treatment using the DiviTumTM assay (Biovica, Sweden).

Results: Among E2F target genes, gene expression data demonstrated that TK1 was one of the most differentially expressed genes between PDR and PDS treated cells. In PDS cells compared to control, treatment with palbociclib resulted in reduced TK1 expression, with the HER2 positive models (BT474 and MDAMB361) showing the highest reduction. In PDR cells, TK1 expression was higher, but remained slightly inhibited compared to untreated PDS cells. TKa was significantly reduced in PDS cells treated with palbociclib for 3 days compared to vehicle (p<0.05). TKa response to palbociclib was more dramatic in BT474 cells as compared to MCF7. As expected, palbociclib inhibited cell proliferation in PDS models, with a significant reduction observed only after 6 days of treatment, suggesting that TKa may be an early marker of growth inhibition in response to palbociclib. No significant alterations in TKa were observed in PDR cells, at any dose of palbociclib. Similarly, proliferation rate was not affected by palbociclib in PDR cells.

Conclusions: TK1 expression and activity are regulated by palbociclib in HR+ breast cancer cell lines, particularly in HER2 positive models. Ongoing studies of TKa in patients treated with palbociclib will assess the role of TKa as a circulating biomarker for predicting and monitoring response to CDK4/6 inhibitors.

Citation Format: Bonechi M, Migliaccio I, Benelli M, Romagnoli D, Bergqvist M, Mattsson K, Boccalini G, Capaccioli G, De Luca F, Galardi F, Biagioni C, Risi E, McCartney A, Rossi L, Osborne CK, Schiff R, De Angelis C, Guarducci C, Di Leo A, Malorni L. Effects of palbociclib on thymidine kinase-1 (TK1) in hormone receptor positive (HR+) breast cancer cell lines [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-09-02.

Abstract P6-02-07: Metabolomic analysis by nuclear magnetic resonance spectroscopy discriminates hormone receptor positive/HER2 negative breast cancer cell lines resistant to palbociclib

Introduction: Clinical trials of palbociclib in combination with endocrine therapy have recently shown unprecedented activity for the treatment of hormone receptor positive/HER2 negative (HR+/HER2neg) advanced breast cancer. However, de novo and acquired resistance to palbociclib limit its clinical utility. Moreover, combining palbociclib with endocrine therapy increases toxicity and costs of the treatment. Identifying patients more likely to benefit from this compound and understanding the mechanisms of resistance to palbociclib is critical. In this study we investigated whether metabolomic profiles of breast cancer cell lines with acquired resistance to palbociclib (PDR) differ from their sensitive counterpart (PDS). In addition we sought to identify metabolic biomarkers of sensitivity to palbociclib by analyzing a breast cancer cell line unable to acquire resistance to palbociclib.

Material and methods: We have established in our lab three PDR HR+/HER2neg breast cancer models (MCF7L, T47D and ZR75-1) by chronically exposing cells to escalating doses of palbociclib. PDR derivatives show IC50 values 6 to 30 times higher than their PDS counterparts. One additional model, CAMA-1, was unable to develop resistance. Whole-cell lysates and conditioned cell culture media from five replicates of each of the PDS and PDR models and from CAMA-1 were analyzed by nuclear magnetic resonance (NMR). Principal component analysis (PCA) was used as first exploratory analysis and as dimension reduction technique. Canonical Analysis (CA) was used to discriminate different groups. Differentially expressed metabolites between PDR and PDS models and between CAMA-1 and PDS cells were analyzed.

Results: Unsupervised PCA analyses of H NMR spectra, in which no information about PDS and PDR was inserted in the statistical model, correctly identified individual cell lines on both whole-cell lysates and conditioned media. However this analysis did not discriminate PDS from PDR within each model. Using a supervised approach, in which the statistical model was trained to discriminate between PDS and PDR, these groups were categorized with accuracy of 80% using whole-cell lysates and of 65% using conditioned media, using a cross-validation analysis by repeatedly testing the model on blind samples. CAMA-1 was correctly identified as a PDS model; however it showed a distinct metabolic profile compared to other PDS models. Over 30 metabolites were identified as differentially expressed between PDS and PDR models in lysates and conditioned media, but only glycerophosphocholine levels in conditioned media remained significantly higher in PDR compared to PDS models after correction for multiple testing.

Conclusions: In this study we show that analysis of metabolic profile of cells lysates discriminates PDR from PDS cell lines with a high accuracy. Analysis of metabolic pathways implicated in resistance/sensitivity to palbociclib is ongoing and might help identifying new targets to overcome resistance. Additionally, metabolites associated with palbociclib resistance may be potentially tested in clinical samples as biomarkers for patients stratification. Further studies are warranted.

Citation Format: Bonechi M, Guarducci C, Meoni G, Tenori L, Biagioni C, Schiff R, Osborne CK, Luchinat C, Di Leo A, Malorni L, Migliaccio I. Metabolomic analysis by nuclear magnetic resonance spectroscopy discriminates hormone receptor positive/HER2 negative breast cancer cell lines resistant to palbociclib [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-02-07.

ES3-3: Adjuvant Therapy in Patients with a Borderline HER-2 Status

Adjuvant trastuzumab is indicated in individuals with early breast cancer which has HER2 gene amplification and/or HER2 protein overexpression. In the pivotal phase III adjuvant trials which tested the addition of trastuzumab to chemotherapy, positive HER2 status was defined as strong and complete cell membrane staining by immunohistochemistry (IHC) of >10% of invasive tumor cells or gene amplification determined by fluorescence in-situ hybridisation (FISH) ratio of HER2 gene copy number to chromosome 17 centromeres (CEP17) of >2.0.

The decision to use trastuzumab is based on a binary categorization of HER2 as positive or negative. As such, the definition of HER2 positivity is critical, as it dictates who will or will not receive potentially efficacious treatment. The challenge in creating guidelines for anti-HER2 treatment is that an HER2 result is described as positive or negative, but HER2 exists as a continuum of gene copy number and protein expression.

A source of uncertainty in the management of patients is the discordance between the diagnostic thresholds for HER2 adopted in the adjuvant trastuzumab trials and those specified in the subsequently published American Society of Clinical Oncology and the College of American Pathologists (ASCO-CAP) guidelines. According to ASCO-CAP, HER2 positivity is defined by uniform intense and complete membrane staining by IHC in ≥30% of cells or HER2/ CEP17 FISH ratio≥2.2. The definition is stricter than thresholds applied in the adjuvant trials, identifying a narrower population as HER2 positive.

A further source of uncertainty is discordance between IHC and FISH. There is generally high concordance between the two methods, as increased HER2 protein is generally attributable to HER2 amplification. Discordant results may occur if one assay is correct and the other is incorrect, due to pre-analytic, analytic, and/or post-analytic error. True discordance may be attributable to intra-tumoral heterogeneity or polysomy chromosome 17. Within a tumor, HER2 amplification and/or overexpression may be detected in discrete focal HER2 amplified clones (FHAC) or in individual cells diffusely scattered on a dominant background of HER2 negative/equivocal expression. FHAC have been reported in association with discordance between IHC and FISH. Cells with polysomy chromosome 17 have extra copies of the HER2 gene. In such cases, tumors may be IHC positive although the HER2:CEP17 FISH ratio is not elevated. Notably, available data are inconsistent and uncertainty remains as to whether polysomy 17 without HER2 amplification is associated with protein overexpression

During this session, clinical situations with borderline HER2−status will be presented and discussed. Biological heterogeneity within the same tumor, polysomy chromosome 17, and moderate HER2 positivity may contribute to determination of an uncertain HER2 status, making unclear the benefit of adjuvant trastuzumab in these cases. Clinical considerations highlighting pros/cons of adjuvant trastuzumab in these cases, as well as updated biological information and clinical perspectives, will be presented.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr ES3-3.

P4-01-18: AP-1 Blockade Potentiates the Anti-Tumor Effect of Endocrine Treatment and Reverts the Resistant Phenotype in Hormone Receptor-Positive Breast Cancer

Background: Resistance to endocrine therapy is a major clinical issue. The transcription factor AP-1 is a key regulator of cell growth and survival as well as a downstream signaling component of several pathways deregulated in endocrine-resistant breast cancer. We have previously shown that acquired endocrine resistance is associated with increased AP-1 activity. AP-1 has also been shown to interact with and modulate the ER network and transcriptional program, especially under hyperactive growth factor signaling, which is commonly associated with endocrine resistance. We hypothesized that interfering with AP-1 function would circumvent endocrine resistance possibly due to its role in modulating ER transcriptional activity.

Methods and results: We inhibited AP-1 function by a genetic approach. We used two different MCF7 clones stably transfected with a Doxycycline (Dox)-inducible dominant-negative (DN) c-Jun (MCF7/Tet-Off Tam67 clones 62 and 67) and two vector-alone control MCF7 clones. Xenografts of these clones were established in ovariectomized nude mice supplemented with estrogen (E2). Mice were then randomized to continued E2 supplementation (control) or to endocrine therapy with either estrogen deprivation (ED) or tamoxifen (Tam), all in the presence or absence of Dox to induce the DN c-Jun expression. AP-1 blockade in both MCF7/Tet-Off Tam67 clones significantly enhanced sensitivity to Tam by reducing time to tumor size halving (p=.014 and p=.006 for clone 62 and 67, respectively) and time to complete tumor disappearance (p=.001 and p=.0034 for clone 62 and 67, respectively). Similar results were obtained with ED treatment. In addition, AP-1 blockade significantly delayed the onset of Tam resistance by increasing time to tumor size doubling (p=.0028). Furthermore, induction of DN c-Jun resulted in a dramatic shrinkage of growing tumors after long-term Tam treatment, suggesting reversal of endocrine resistance with AP-1 blockade. None of the above effects was observed in control clones upon Dox removal. Interestingly, no significant effect of AP-1 blockade was observed on E2-stimulated tumor growth. IHC analysis showed that AP-1 blockade induced tumor response by reducing proliferation (i.e., decreased % of Ki67- and phospho-Histone 3-positive cells) and by inducing apoptosis (i.e., increased % of cleaved caspase 3/7-positive cells). Bioinformatic analyses were conducted to intersect our MCF7 xenograft/Tam-resistant gene signature and the datasets of genes associated with ER DNA-binding sites obtained by whole-genome ER cistromic analysis under estrogen or epidermal growth factor (EGF) stimulation of MCF7 cells. A significant enrichment of the genes associated with the EGF-unique ER DNA-binding sites was observed within our Tam-resistant signature (p<2E-16). Remarkably, 90% of these DNA binding sites harbored an AP-1 motif.

Conclusions: We show that AP-1 blockade increases tumor sensitivity and circumvents resistance to endocrine therapy, thus warranting the development of AP-1-targeted therapy to improve endocrine treatment outcomes. Overall, we suggest that AP-1 is critical in induction of a switch in the ER transcriptional program and may be a new hallmark of endocrine resistance.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-18.

Abstract P2-06-09: Mucin4 Is Associated with the Loss of Estrogen-Receptor-α in Breast Cancer

Data suggests that breast carcinomas that overexpress the HER2 oncoprotein are more resistant to endocrine treatments such as tamoxifen (Tam) or estrogen deprivation (ED) via aromatase inhibitors. To investigate possible mechanisms of endocrine resistance in vivo, we performed a gene microarray analysis on estrogen receptor-(ER)+, HER2-overexpressing xenograft tumors that are de novo resistant to tamoxifen treatment and acquire resistance to ED therapy. A large number of genes were upregulated, including several members of the mucin family of genes. This corroborated our finding from histological staining of the resistant tumors that indicated striking increases of mucin vacuoles when compared to sensitive tumors. These vacuoles were located mostly intracellularly and stained positive for mucins with mucicarmine. We were particularly interested in one particular mucin, mucin4 (MUC4) because previous studies have suggested its role in stabilizing and enhancing HER2 signaling. Quantitative realtime PCR confirmed the microarray results and showed that there was an approximately 156-fold increase in MUC4 transcript between the ED-sensitive and ED-resistant tumors, with a 65-fold increase between the early Tam and late Tam-resistant tumors. Immunohistochemistry confirmed that this upregulation in these two treatment groups was present also at the protein level. Furthermore, western blot analysis of these tumors demonstrated that resistant tumors have downregulation of ER protein and its downstream effectors with corresponding increase in total HER2 protein levels. These tumors have seemingly shifted away from the ER pathway to signaling via the growth factor signaling pathway. Preliminary experiments where MUC4 protein was stably overexpressed in ER+, HER2-overexpressing cells model these results in vitro with a downregulation of ER protein and downstream effectors, showing that ER expression and activity are affected. Furthermore, immunohistochemical analysis of 73 primary human invasive breast carcinomas suggests that MUC4 is associated with estrogen-receptor negative tumors (P=0.05). This clinical data validates the preclinical studies for investigating a possible mechanism for the loss of ER, and suggest MUC4 as an inviting biomarker for endocrine treatment and a potential therapeutic target for endocrine resistant breast cancer.

Crosstabulation of MUC4 and ER

Abstract S6-10: Identification of a Novel Tumor Suppressor Network Reveals a Role for Proto-Oncogenic Receptor Tyrosine Kinases in Triple-Negative Breast Cancer

Breast cancer is a collection of diseases with distinct clinical behaviors and underlying genetic causes. Triple-negative breast cancer (TNBC) is a common subtype of breast cancer that confers a particularly poor prognosis and is refractory to current targeted therapies. Unfortunately, the molecular determinants driving this aggressive malignancy are poorly understood. Using an unbiased genetic screen, we have identified a novel tumor suppressor network that governs proliferation and transformation of TNBCs in vitro and in vivo. We define SECT21 as a core component in this network and a commonly inactivated tumor suppressor in TNBC. SECT21 is a potent suppressor of human mammary epithelial cell proliferation and transformation. SECT21 function is frequently compromised in human TNBCs by inactivating mutations, deletion, or loss of protein expression. Mechanistically, SECT21 is a tyrosine phosphatase that suppresses cellular transformation by interacting with and inhibiting several oncogenic receptor tyrosine kinases including HER2, EGFR, and PDGFR. Notably, the tumorigenic and metastatic potential of SECT21-deficient TNBCs is severely impaired by restoring SECT21 function or by inhibiting kinase targets of SECT21, suggesting that TNBCs are dependent on the proto-oncogenic tyrosine kinases constrained by SECT21. Collectively, these data identify SECT21 as a commonly inactivated tumor suppressor and provide a rationale for combinatorially targeting tyrosine kinases in TNBC and other cancers based on their profile of tyrosine phosphatase activity.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr S6-10.

UbcH10 overexpression may represent a marker of anaplastic thyroid carcinomas

The hybridisation of an Affymetrix HG_U95Av2 oligonucleotide array with RNAs extracted from six human thyroid carcinoma cell lines and a normal human thyroid primary cell culture led us to the identification of the UbcH10 gene that was upregulated by 150-fold in all of the carcinoma cell lines in comparison to the primary culture cells of human normal thyroid origin. Immunohistochemical studies performed on paraffin-embedded tissue sections showed abundant UbcH10 levels in thyroid anaplastic carcinoma samples, whereas no detectable UbcH10 expression was observed in normal thyroid tissues, in adenomas and goiters. Papillary and follicular carcinomas were only weakly positive. These results were further confirmed by RT-PCR and Western blot analyses. The block of UbcH10 protein synthesis induced by RNA interference significantly reduced the growth rate of thyroid carcinoma cell lines. Taken together, these results would indicate that UbcH10 overexpression is involved in thyroid cell proliferation, and may represent a marker of thyroid anaplastic carcinomas.