Interplay of OATP1A/1B/2B1 uptake transporters and ABCB1 and ABCG2 efflux transporters in the handling of bilirubin and drugs.

Transmembrane drug transporters can be important determinants of the pharmacokinetics, efficacy, and safety profiles of drugs. To investigate the potential cooperative and/or counteracting interplay of OATP1A/1B/2B1 uptake transporters and ABCB1 and ABCG2 efflux transporters in physiology and pharmacology, we generated a new mouse model (Bab12), deficient for Slco1a/1b, Slco2b1, Abcb1a/1b and Abcg2. Bab12 mice were viable and fertile. We compared wild-type, Slco1a/1b/2b1-/-, Abcb1a/1b;Abcg2-/- and Bab12 strains. Endogenous plasma conjugated bilirubin levels ranked as follows: wild-type = Abcb1a/1b;Abcg2-/- << Slco1a/1b/2b1-/- < Bab12 mice. Plasma levels of rosuvastatin and fexofenadine were elevated in Slco1a/1b/2b1-/- and Abcb1a/1b;Abcg2-/- mice compared to wild-type, and dramatically increased in Bab12 mice. Although systemic exposure of larotrectinib and repotrectinib was substantially increased in the separate multidrug transporter knockout strains, no additive effects were observed in the combination Bab12 mice. Significantly higher plasma exposure of fluvastatin and pravastatin was only found in Slco1a/1b/2b1-deficient mice. However, noticeable transport by Slco1a/1b/2b1 and Abcb1a/1b and Abcg2 across the BBB was observed for fluvastatin and pravastatin, respectively, by comparing Bab12 mice with Abcb1a/1b;Abcg2-/- or Slco1a/1b/2b1-/- mice. Quite varying behavior in plasma exposure of erlotinib and its metabolites was observed among these strains. Bab12 mice revealed that Abcb1a/1b and/or Abcg2 can contribute to conjugated bilirubin elimination when Slco1a/1b/2b1 are absent. Our results suggest that the interplay of Slco1a/1b/2b1, Abcb1a/1b, and Abcg2 could markedly affect the pharmacokinetics of some, but not all drugs and metabolites. The Bab12 mouse model will represent a useful tool for optimizing drug development and clinical application, including efficacy and safety.

Organic anion-transporting polypeptide 2B1 knockout and humanized mice; insights into the handling of bilirubin and drugs.

Organic anion transporting polypeptide 2B1 (OATP2B1/SLCO2B1) facilitates uptake transport of structurally diverse endogenous and exogenous compounds. To investigate the roles of OATP2B1 in physiology and pharmacology, we established and characterized Oatp2b1 knockout (single Slco2b1-/- and combination Slco1a/1b/2b1-/-) and humanized hepatic and intestinal OATP2B1 transgenic mouse models. While viable and fertile, these strains exhibited a modestly increased body weight. In males, unconjugated bilirubin levels were markedly reduced in Slco2b1-/- compared to wild-type mice, whereas bilirubin monoglucuronide levels were modestly increased in Slco1a/1b/2b1-/- compared to Slco1a/1b-/- mice. Single Slco2b1-/- mice showed no significant changes in oral pharmacokinetics of several tested drugs. However, markedly higher or lower plasma exposure of pravastatin and the erlotinib metabolite OSI-420, respectively, were found in Slco1a/1b/2b1-/- compared to Slco1a/1b-/- mice, while oral rosuvastatin and fluvastatin behaved similarly between the strains. In males, humanized OATP2B1 strains showed lower conjugated and unconjugated bilirubin levels than control Slco1a/1b/2b1-deficient mice. Moreover, hepatic expression of human OATP2B1 partially or completely rescued the impaired hepatic uptake of OSI-420, rosuvastatin, pravastatin, and fluvastatin in Slco1a/1b/2b1-/- mice, establishing an important role in hepatic uptake. Expression of human OATP2B1 in the intestine was basolateral and markedly reduced the oral availability of rosuvastatin and pravastatin, but not of OSI-420 and fluvastatin. Neither lack of Oatp2b1, nor overexpression of human OATP2B1 had any effect on fexofenadine oral pharmacokinetics. While these mouse models still have limitations for human translation, with additional work we expect they will provide powerful tools to further understand the physiological and pharmacological roles of OATP2B1.

[Prophylactic mastectomy and occult cancer: a ten-year experience at a cancer center]. / Chirurgie de réduction de risque mammaire et découverte fortuite de cancer : dix ans d'expérience dans un centre de lutte contre le cancer.

INTRODUCTION: Women identified as high-risk for breast cancer may choose between close follow-up and radical mastectomy. Prophylactic mastectomy, as any other surgery, is associated with benefits and harms. The aim of this study was to assess the morbidity associated with prophylactic mastectomy and to evaluate the prevalence of occult cancers. METHODS: All patients who underwent unilateral or bilateral prophylactic mastectomy between 2007 and 2017 in our institution were eligible for inclusion in this retrospective study. Medical history, type of surgery, occurrence of complication or reoperation and pathological reports were examined in medical charts. RESULTS: 79 women underwent prophylactic mastectomy over the studied period of which 58.2% were contralateral after breast cancer. A genetic mutation was present in 86.1% of cases. Postoperative complications occurred in 43.0% of cases. An additional surgery for medical or esthetic purpose was needed in 72.1% of cases. Occult cancer was found in 11.4% of the pathological reports. Triple negative invasive ductal carcinoma was discovered in two cases (2.5%). DISCUSSION: Prophylactic mastectomy is the only effective preventive action against breast cancer. Women must be clearly informed of possible complications, high reoperation rate and potential pathological findings. Identifying women most at risk for breast cancer would help to better target those who will benefit most from surgery.

Diagnostic accuracy of breast MRI for patients with suspicious nipple discharge and negative mammography and ultrasound: a prospective study.

OBJECTIVES: To evaluate the diagnostic accuracy of breast MRI in identifying lesions requiring excision for patients with suspicious nipple discharge but normal mammograms and ultrasounds. METHODS: Between September 2013 and May 2019, 106 female participants (mean age 57.9 years) were consecutively included in this prospective multicenter study; 102 were retained for analysis. MRI was considered negative in the absence of suspicious enhancement and positive in cases of ipsilateral abnormal enhancement (BI-RADS 3 to 5). Final diagnoses were based on histological findings of surgical or percutaneous biopsies or at 1-year follow-up. We considered all lesions requiring excision found on pathology (papilloma, atypia, nipple adenomatosis, or cancer) as positive results. We considered spontaneous resolution of the discharge at 1 year as a negative result. RESULTS: MRI showed ipsilateral abnormal enhancement in 54 patients (53%) revealing 46 lesions requiring excision (31 benign papillomas, 5 papillomas with atypia, 2 nipple adenomatosis, and 8 cancers) and 8 benign lesions not requiring excision. No suspicious enhancement was found in the remaining 48 participants (47%). Forty-two were followed up at 1 year with spontaneous resolution of the discharge and six underwent surgery (revealing 2 benign papillomas). MRI diagnostic accuracy for the detection of a lesion requiring excision was as follows: sensitivity 96%, specificity 85%, positive predictive value 85%, and negative predictive value 96%. CONCLUSION: In patients with suspicious nipple discharge and normal mammogram and ultrasound, MRI demonstrates excellent performance to identify lesions for which excision is required. Normal MRI indicates it is safe to propose follow-up only management, thus avoiding unnecessary duct excision. TRIAL REGISTRATION: ClinicalTrials.gov NCT02819362 KEY POINTS: • Breast MRI can be useful for the management of patients with suspicious nipple discharge and negative mammogram and ultrasound. • MRI detected a lesion requiring excision in 46 participants (45%) with unexplained discharge. • If breast MRI is negative, follow-up is a safe alternative for these patients.

Extrahepatic metabolism of ibrutinib.

Ibrutinib is a first-in-class Bruton's kinase inhibitor used in the treatment of multiple lymphomas. In addition to CYP3A4-mediated metabolism, glutathione conjugation can be observed. Subsequently, metabolism of the conjugates and finally their excretion in feces and urine occurs. These metabolites, however, can reach substantial concentrations in human subjects, especially when CYP3A4 is inhibited. Ibrutinib has unexplained nephrotoxicity and high metabolite concentrations are also found in kidneys of Cyp3a knockout mice. Here, a mechanism is proposed where the intermediate cysteine metabolite is bioactivated. The metabolism of ibrutinib through this glutathione cycle was confirmed in cultured human renal proximal tubule cells. Ibrutinib-mediated toxicity was enhanced in-vitro by inhibitors of breast cancer resistance protein (BCRP), P-glycoprotein (P-gp) and multidrug resistance protein (MRP). This was a result of accumulating cysteine metabolite levels due to efflux inhibition. Finally, through inhibition of downstream metabolism, it was shown now that direct conjugation was responsible for cysteine metabolite toxicity.

New insights in the reproducibility of visual and electronic tooth color assessment for dental practice.

BACKGROUND: The aim of the study was to compare a 2D and 3D color system concerning a variety of statistical and graphical methods to assess validity and reliability of color measurements, and provide guidance on when to use which system and how to interpret color distance measures, including ΔE and d(0M1). METHODS: The color of teeth 14 to 24 of 35 patients undergoing regular bleaching treatment was visually assessed and electronically measured with the spectrophotometer Shade Inspector™. Tooth color was recorded before bleaching treatment, after 14 days, and again after 6 months. VITAPAN® Classical (2D) and VITA-3D-Master® (3D) served as reference systems. RESULTS: Concerning repeated measurements, the 2D system was superior to the 3D system, both visually and electronically in terms of ΔE and d(OM1), for statistics of agreement and reliability. All four methods showed strong patterns in Bland-Altman plots. In the 3D system, hue was less reliable than lightness and chroma, which was more pronounced visually than electronically. The smallest detectable color difference varied among the four methods used, and was most favorable in the electronic 2D system. Comparing the methods, the agreement between the 2D and 3D system in terms of ΔE was not good. The reliability of the visual and electronic method was essentially the same in the 2D and 3D systems; this comparability is fair to good. CLINICAL RELEVANCE: The 3D system may confuse human raters and even electronic devices. The 2D system is the simple and best choice.

Residual cancer burden index and tumor-infiltrating lymphocyte subtypes in triple-negative breast cancer after neoadjuvant chemotherapy.

PURPOSE: There is a need to refine the prognosis of triple-negative breast cancer (TNBC) patients after neoadjuvant chemotherapy (NAC) and to study the influence of the tumor microenvironment. We evaluated the prognostic value of pathological and immune markers in TNBC with residual disease (RD) after NAC. METHODS: In a series of 186 TNBC patients treated by NAC, we assessed the prognostic value of the Residual Cancer Burden (RCB) index. In 109 patients with RD, we studied the impact of clinicopathological features and tumor immune response in the residual tumor on overall survival (OS) and distant recurrence-free interval (DRFI). RESULTS: In the whole group, the OS and DRFI, at 3 years, were statistically different between the different classes of RCB (P = 0.0004 and P < 0.0001, respectively). In univariate analysis of the RD group, low RCB index and high ratios of stromal tumor-infiltrating lymphocytes (TILs), CD3 + TILs, CD4 + TILs, CD8 + TILs, and IDO1-positive cells were significant favorable prognostic factors for DRFI at 3 years. In the final multivariate model, CD4 + TILs and RCB index showed a statistically independent prognostic significance for DRFI [Hazard Ratio (HR) 2.88 (95%CI 1.34-6.17), P = 0.007 and HR 12.04 (95%CI 2.78-52.23, P < 0.0001), respectively]. The CD4 + TIL levels influenced survival in the different RCB classes with a significant effect observed in RCB-II and RCB-III classes (P = 0.05 and P = 0.05, respectively). CONCLUSIONS: These results suggest that the combination of pathological (RCB index) and tumor micro-environmental features (CD4 + TILs) help refining the prognosis of TNBC patients with RD following NAC.

P-glycoprotein Limits Ribociclib Brain Exposure and CYP3A4 Restricts Its Oral Bioavailability.

Ribociclib is a CDK4/6 inhibitor recently approved for the treatment of some types of breast cancer in combination with an aromatase inhibitor. It is currently investigated in the clinic to treat other malignancies, including brain tumors. Using in vitro and genetically modified mouse models, we investigated the effect of the multidrug efflux transporters ABCB1 and ABCG2, and the drug-metabolizing CYP3A enzymes on ribociclib pharmacokinetics and tissue distribution. In vitro, ribociclib was avidly transported by human ABCB1, but not by human ABCG2 and only modestly by mouse Abcg2. Upon oral administration at 20 mg/kg, the plasma AUC0-24h of ribociclib was increased by 2.3-fold, and its terminal elimination was delayed in Abcb1a/1b-/-;Abcg2-/- compared to wild-type mice. The brain-to-plasma ratios of ribociclib were increased by at least 23-fold relative to wild-type mice in Abcb1a/1b-/-;Abcg2-/- and Abc1a/1b-/- mice, but not noticeably in Abcg2-/- mice. Oral coadministration of elacridar, an ABCB1 and ABCG2 inhibitor, increased the brain penetration of ribociclib in wild-type mice to the same level as seen in Abcb1a/1b-/-;Abcg2-/- mice. Plasma exposure of ribociclib further decreased by 3.8-fold when transgenic human CYP3A4 was overexpressed in Cyp3a-deficient mice. Ribociclib penetration into the brain is thus drastically limited by ABCB1 in the blood-brain barrier, but coadministration of elacridar can fully reverse this process. Moreover, human CYP3A4 can extensively metabolize ribociclib and strongly restrict its oral bioavailability. The insights obtained from this study may be useful to further optimize the clinical application of ribociclib, especially for the treatment of (metastatic) brain tumors.

Brain accumulation of osimertinib and its active metabolite AZ5104 is restricted by ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein).

Osimertinib is an irreversible EGFR inhibitor registered for advanced NSCLC patients whose tumors harbor recurrent somatic activating mutations in EGFR (EGFRm+) or the frequently occurring EGFR-T790M resistance mutation. Using in vitro transport assays and appropriate knockout and transgenic mouse models, we investigated whether the multidrug efflux transporters ABCB1 and ABCG2 transport osimertinib and whether they influence the oral availability and brain accumulation of osimertinib and its most active metabolite, AZ5104. In vitro, human ABCB1 and mouse Abcg2 modestly transported osimertinib. In mice, Abcb1a/1b, with a minor contribution of Abcg2, markedly limited the brain accumulation of osimertinib and AZ5104. However, no effect of the ABC transporters was seen on osimertinib oral availability. In spite of up to 6-fold higher brain accumulation, we observed no acute toxicity signs of oral osimertinib in Abcb1a/1b;Abcg2 knockout mice. Interestingly, even in wild-type mice the intrinsic brain penetration of osimertinib was already relatively high, which may help to explain the documented partial efficacy of this drug against brain metastases. No substantial effects of mouse Cyp3a knockout or transgenic human CYP3A4 overexpression on oral osimertinib pharmacokinetics were observed, presumably due to a dominant role of mouse Cyp2d enzymes in osimertinib metabolism. Our results suggest that pharmacological inhibition of ABCB1 and ABCG2 during osimertinib therapy might potentially be considered to further benefit patients with brain (micro-)metastases positioned behind an intact blood-brain barrier, or with substantial expression of these transporters in the tumor cells, without invoking a high toxicity risk.

Performance Evaluation of MHC Class-I Binding Prediction Tools Based on an Experimentally Validated MHC-Peptide Binding Data Set.

Knowing whether a protein can be processed and the resulting peptides presented by major histocompatibility complex (MHC) is highly important for immunotherapy design. MHC ligands can be predicted by in silico peptide-MHC class-I binding prediction algorithms. However, prediction performance differs considerably, depending on the selected algorithm, MHC class-I type, and peptide length. We evaluated the prediction performance of 13 algorithms based on binding affinity data of 8- to 11-mer peptides derived from the HPV16 E6 and E7 proteins to the most prevalent human leukocyte antigen (HLA) types. Peptides from high to low predicted binding likelihood were synthesized, and their HLA binding was experimentally verified by in vitro competitive binding assays. Based on the actual binding capacity of the peptides, the performance of prediction algorithms was analyzed by calculating receiver operating characteristics (ROC) and the area under the curve (AROC). No algorithm outperformed others, but different algorithms predicted best for particular HLA types and peptide lengths. The sensitivity, specificity, and accuracy of decision thresholds were calculated. Commonly used decision thresholds yielded only 40% sensitivity. To increase sensitivity, optimal thresholds were calculated, validated, and compared. In order to make maximal use of prediction algorithms available online, we developed MHCcombine, a web application that allows simultaneous querying and output combination of up to 13 prediction algorithms. Taken together, we provide here an evaluation of peptide-MHC class-I binding prediction tools and recommendations to increase prediction sensitivity to extend the number of potential epitopes applicable as targets for immunotherapy.

SOX10, GATA3, GCDFP15, Androgen Receptor, and Mammaglobin for the Differential Diagnosis Between Triple-negative Breast Cancer and TTF1-negative Lung Adenocarcinoma.

Triple-negative breast cancer (TNBC) patients have an increased risk of developing visceral metastases and other primary nonbreast cancers, particularly lung cancer. The differential diagnosis of TNBC metastases and primary cancers from other organs can be difficult due to lack of a TNBC standard immunoprofile. We analyzed the diagnostic value of estrogen receptor, progesterone receptor, human epidermal growth factor receptor, thyroid transcription factor-1 (TTF1), Napsin A, mammaglobin, gross cystic disease fluid protein 15 (GCDFP15), Sry-related HMg-Box gene 10 (SOX10), GATA-binding protein 3 (GATA3), and androgen receptor in a series of 207 TNBC and 152 primary lung adenocarcinomas (LA). All tested TNBCs were TTF1 and Napsin A-negative. When comparing TNBC and TTF1-positive or negative LA, SOX10 had the best sensitivity (62.3%) and specificity (100%) as a marker in favor of TNBC compared with LA, irrespective of TTF1 status (P<0.0001). GATA3 had moderate sensitivity (30.4%) and excellent specificity (98.7%) and misclassified only 2/152 LA (1.3%). GCDFP15 had a moderate sensitivity (20.8%) and excellent specificity (98%) and misclassified only 3/152 (2%) LA. Mammaglobin and androgen receptor had moderate sensitivities (38.2% and 30%), good specificities (81.6% and 86%), and misclassified 28/152 and 21/152 LAs, respectively. In multivariate analysis, the best markers, enabling the distinction between SOX10-negative TNBC and TTF1 and Napsin A-negative LA were GATA3 (odds ratio=33.5; 95% confidence interval, 7.3-153.5; P<0.0001) and GCDFP15 (odds ratio=31.7; 95% confidence interval, 6.9-145.6; P<0.0001). Only 13/207 (6.3%) TNBC cases did not express any aforementioned marker. On the basis of our results, the best sequential immunohistochemical analysis to differentiate TNBC from TTF1-negative LA is first SOX10 followed by GATA3, and finally GCDFP15. This order is important in the diagnostic workup of small biopsies from lung nodules in women with a previous history of TNBC.

P-Glycoprotein (MDR1/ABCB1) Restricts Brain Penetration of the Bruton's Tyrosine Kinase Inhibitor Ibrutinib, While Cytochrome P450-3A (CYP3A) Limits Its Oral Bioavailability.

Ibrutinib (Imbruvica), an oral tyrosine kinase inhibitor (TKI) approved for treatment of B-cell malignancies, irreversibly inhibits the Bruton's tyrosine kinase (BTK). Its abundant metabolite, dihydrodiol-ibrutinib (ibrutinib-DiOH), which is primarily formed by CYP3A, has a 10-fold reduced BTK inhibitory activity. Using in vitro transport assays and genetically modified mouse models, we investigated whether the multidrug efflux transporters ABCB1 and ABCG2 and the multidrug-metabolizing CYP3A enzyme family can affect the oral bioavailability and tissue disposition of ibrutinib and ibrutinib-DiOH. In vitro, ibrutinib was transported moderately by human ABCB1 and mouse Abcg2 but not detectably by human ABCG2. In mice, Abcb1 markedly restricted the brain penetration of ibrutinib and ibrutinib-DiOH, either alone or in combination with Abcg2, resulting in 4.5- and 5.9-fold increases in ibrutinib brain-to-plasma ratios in Abcb1a/1b-/- and Abcb1a/1b;Abcg2-/- mice relative to wild-type mice. Abcb1 and/or Abcg2 did not obviously restrict ibrutinib oral bioavailability, but Cyp3a deficiency increased the ibrutinib plasma AUC by 9.7-fold compared to wild-type mice. This increase was mostly reversed (5.1-fold reduction) by transgenic human CYP3A4 overexpression, with roughly equal contributions of intestinal and hepatic CYP3A4 metabolism. Our results suggest that pharmacological inhibition of ABCB1 during ibrutinib therapy might benefit patients with malignancies or (micro)metastases positioned behind an intact blood-brain barrier, or with substantial expression of this transporter in the malignant cells. Moreover, given the strong in vivo impact of CYP3A, inhibitors or inducers of this enzyme family will likely strongly affect ibrutinib oral bioavailability and, thus, its therapeutic efficacy, as well as its toxicity risks.

A Targeted LC-MS Strategy for Low-Abundant HLA Class-I-Presented Peptide Detection Identifies Novel Human Papillomavirus T-Cell Epitopes.

For rational design of therapeutic vaccines, detailed knowledge about target epitopes that are endogenously processed and truly presented on infected or transformed cells is essential. Many potential target epitopes (viral or mutation-derived), are presented at low abundance. Therefore, direct detection of these peptides remains a challenge. This study presents a method for the isolation and LC-MS3 -based targeted detection of low-abundant human leukocyte antigen (HLA) class-I-presented peptides from transformed cells. Human papillomavirus (HPV) was used as a model system, as the HPV oncoproteins E6 and E7 are attractive therapeutic vaccination targets and expressed in all transformed cells, but present at low abundance due to viral immune evasion mechanisms. The presented approach included preselection of target antigen-derived peptides by in silico predictions and in vitro binding assays. The peptide purification process was tailored to minimize contaminants after immunoprecipitation of HLA-peptide complexes, while keeping high isolation yields of low-abundant target peptides. The subsequent targeted LC-MS3 detection allowed for increased sensitivity, which resulted in successful detection of the known HLA-A2-restricted epitope E711-19 and ten additional E7-derived peptides on the surface of HPV16-transformed cells. T-cell reactivity was shown for all the 11 detected peptides in ELISpot assays, which shows that detection by our approach has high predictive value for immunogenicity. The presented strategy is suitable for validating even low-abundant candidate epitopes to be true immunotherapy targets.

P-glycoprotein (MDR1/ABCB1) and Breast Cancer Resistance Protein (BCRP/ABCG2) affect brain accumulation and intestinal disposition of encorafenib in mice.

Encorafenib (LGX818) is a promising BRAFV600E inhibitor that has efficacy against metastatic melanoma. To better understand its pharmacokinetics, we studied its interactions with the multidrug efflux transporters ABCB1 and ABCG2 and the multidrug metabolizing enzyme CYP3A. In polarized MDCK-II cells, encorafenib was efficiently transported by canine and human ABCB1 and ABCG2 and by mouse Abcg2. Upon oral administration to wild-type, Abcb1a/1b-/-, Abcg2-/-, and Abcb1a/1b;Abcg2-/- mice, encorafenib was absorbed very quickly and to very high plasma levels, but without clear changes in oral availability between the strains. Upon oral or intravenous administration, encorafenib brain accumulation was markedly increased in Abcb1a/1b;Abcg2-/- mice and to a lesser extent in Abcb1a/1b-/- mice. However, absolute brain concentrations and brain-to-plasma ratios remained very low in all strains, indicating intrinsically poor brain penetration of encorafenib. Upon intravenous administration, Abcb1a/1b;Abcg2-/- mice showed somewhat reduced plasma elimination of encorafenib compared to wild-type mice, and lower accumulation of the drug in the intestinal tract, suggesting a limited role for these transporters in intestinal elimination of the drug. In Cyp3a-/- mice plasma levels of encorafenib were not markedly increased, suggesting a limited impact of Cyp3a on encorafenib oral availability. The low brain penetration of encorafenib might limit its efficacy against malignancies positioned behind a functional blood-brain barrier, but its oral bioavailability and distribution to other tested organs (liver, kidney, spleen, testis) was high.

Brain Accumulation of Ponatinib and Its Active Metabolite, N-Desmethyl Ponatinib, Is Limited by P-Glycoprotein (P-GP/ABCB1) and Breast Cancer Resistance Protein (BCRP/ABCG2).

Ponatinib is an oral BCR-ABL1 inhibitor for treatment of advanced leukemic diseases that carry the Philadelphia chromosome, specifically containing the T315I mutation yielding resistance to previously approved BCR-ABL1 inhibitors. Using in vitro transport assays and knockout mouse models, we investigated whether the multidrug efflux transporters ABCB1 and ABCG2 transport ponatinib and whether they, or the drug-metabolizing enzyme CYP3A, affect the oral availability and brain accumulation of ponatinib and its active N-desmethyl metabolite (DMP). In vitro, mouse Abcg2 and human ABCB1 modestly transported ponatinib. In mice, both Abcb1 and Abcg2 markedly restricted brain accumulation of ponatinib and DMP, but not ponatinib oral availability. Abcg2 deficiency increased DMP plasma levels ∼3-fold. Cyp3a deficiency increased the ponatinib plasma AUC 1.4-fold. Our results suggest that pharmacological inhibition of ABCG2 and ABCB1 during ponatinib therapy might benefit patients with brain (micro)metastases positioned behind an intact blood-brain barrier, or with substantial expression of these transporters in the malignant cells. CYP3A inhibitors might increase ponatinib oral availability, enhancing efficacy but possibly also toxicity of this drug.

ERAP1 overexpression in HPV-induced malignancies: A possible novel immune evasion mechanism.

Immune evasion of tumors poses a major challenge for immunotherapy. For human papillomavirus (HPV)-induced malignancies, multiple immune evasion mechanisms have been described, including altered expression of antigen processing machinery (APM) components. These changes can directly influence epitope presentation and thus T-cell responses against tumor cells. To date, the APM had not been studied systematically in a large array of HPV+ tumor samples. Therefore in this study, systematic expression analysis of the APM was performed on the mRNA and protein level in a comprehensive collection of HPV16+ cell lines. Subsequently, HPV+ cervical tissue samples were examined by immunohistochemistry. ERAP1 (endoplasmic reticulum aminopeptidase 1) was the only APM component consistently altered - namely overexpressed - in HPV16+ tumor cell lines. ERAP1 was also found to be overexpressed in cervical intraepithelial neoplasia and cervical cancer samples; expression levels were increasing with disease stage. On the functional level, the influence of ERAP1 expression levels on HPV16 E7-derived epitope presentation was investigated by mass spectrometry and in cytotoxicity assays with HPV16-specific T-cell lines. ERAP1 overexpression did not cause a complete destruction of any of the HPV epitopes analyzed, however, an influence of ERAP1 overexpression on the presentation levels of certain HPV epitopes could be demonstrated by HPV16-specific CD8+ T-cells. These showed enhanced killing toward HPV16+ CaSki cells whose ERAP1 expression had been attenuated to normal levels. ERAP1 overexpression may thus represent a novel immune evasion mechanism in HPV-induced malignancies, in cases when presentation of clinically relevant epitopes is reduced by overactivity of this peptidase.

Hepatic uptake of conjugated bile acids is mediated by both sodium taurocholate cotransporting polypeptide and organic anion transporting polypeptides and modulated by intestinal sensing of plasma bile acid levels in mice.

The Na+ -taurocholate cotransporting polypeptide (NTCP/SLC10A1) is believed to be pivotal for hepatic uptake of conjugated bile acids. However, plasma bile acid levels are normal in a subset of NTCP knockout mice and in mice treated with myrcludex B, a specific NTCP inhibitor. Here, we elucidated which transport proteins mediate the hepatic uptake of conjugated bile acids and demonstrated intestinal sensing of elevated bile acid levels in plasma in mice. Mice or healthy volunteers were treated with myrcludex B. Hepatic bile acid uptake kinetics were determined in wild-type (WT), organic anion transporting polypeptide (OATP) knockout mice (lacking Slco1a/1b isoforms), and human OATP1B1-transgenic mice. Effects of fibroblast growth factor 19 (FGF19) on hepatic transporter mRNA levels were assessed in rat hepatoma cells and in mice by peptide injection or adeno-associated virus-mediated overexpression. NTCP inhibition using myrcludex B had only moderate effects on bile acid kinetics in WT mice, but completely inhibited active transport of conjugated bile acid species in OATP knockout mice. Cholesterol 7α-hydroxylase Cyp7a1 expression was strongly down-regulated upon prolonged inhibition of hepatic uptake of conjugated bile acids. Fgf15 (mouse counterpart of FGF19) expression was induced in hypercholanemic OATP and NTCP knockout mice, as well as in myrcludex B-treated cholestatic mice, whereas plasma FGF19 was not induced in humans treated with myrcludex B. Fgf15/FGF19 expression was induced in polarized human enterocyte-models and mouse organoids by basolateral incubation with a high concentration (1 mM) of conjugated bile acids. CONCLUSION: NTCP and OATPs contribute to hepatic uptake of conjugated bile acids in mice, whereas the predominant uptake in humans is NTCP mediated. Enterocytes sense highly elevated levels of (conjugated) bile acids in the systemic circulation to induce FGF15/19, which modulates hepatic bile acid synthesis and uptake. (Hepatology 2017;66:1631-1643).

Breast cancer resistance protein (BCRP/ABCG2) and P-glycoprotein (P-gp/ABCB1) transport afatinib and restrict its oral availability and brain accumulation.

Afatinib is a highly selective, irreversible inhibitor of EGFR and HER-2. It is orally administered for the treatment of patients with EGFR mutation-positive types of metastatic NSCLC. We investigated whether afatinib is a substrate for the multidrug efflux transporters ABCB1 and ABCG2 and whether these transporters influence oral availability and brain and other tissue accumulation of afatinib. We used in vitro transport assays to assess human (h)ABCB1-, hABCG2- or murine (m)Abcg2-mediated transport of afatinib. To study the single and combined roles of Abcg2 and Abcb1a/1b in oral afatinib disposition, we used appropriate knockout mouse strains. Afatinib was transported well by hABCB1, hABCG2 and mAbcg2 in vitro. Upon oral administration of afatinib, Abcg2-/-, Abcb1a/1b-/- and Abcb1a/1b-/-;Abcg2-/- mice displayed a 4.2-, 2.4- and 7-fold increased afatinib plasma AUC0-24 compared with wild-type mice. Abcg2-deficient strains also displayed decreased afatinib plasma clearance. At 2h, relative brain accumulation of afatinib was not significantly altered in the single knockout strains, but 23.8-fold increased in Abcb1a/1b-/-;Abcg2-/- mice compared to wild-type mice. Abcg2 and Abcb1a/1b restrict oral availability and brain accumulation of afatinib. Inhibition of these transporters may therefore be of clinical importance for patients with brain (micro)metastases positioned behind an intact blood-brain barrier.

Helical tomotherapy of spinal chordomas: French Multicentric, retrospective study of a cohort of 30 cases.

PURPOSE: To evaluate the efficacy and toxicity of helical tomotherapy (HT) in the management of spine chordomas when proton therapy is unavailable or non-feasible. METHODS AND MATERIALS: Between 2007 and 2013, 30 patients with biopsy-proven chordomas were treated by HT in five French institutions. Information regarding local control (LC), overall survival (OS), progression-free survival (PFS) and metastasis-free survival (MFS) was collected. Clinical efficacy, toxicity and treatment quality were evaluated. RESULTS: Two-year actuarial LC, OS, PFS and MFS were 69.9%, 96.7%, 61.2% and 76.4%, respectively. HT treatments were well tolerated and no Grade 4-5 toxicities were observed. HT permitted the delivery of a mean dose of 68 Gy while respecting organ at risk (OAR) dose constraints, in particular in the spinal cord and cauda equina. CONCLUSIONS: This multicentric, retrospective study demonstrated the feasibility of HT in the treatment of spine chordomas, in the absence of hadron therapy.