Liver Regeneration Following Radiation Therapy in Hepatocellular Carcinoma Patients: Insights from Functional Liver Imaging

PURPOSE/OBJECTIVE(S)

A critical need for hepatocellular carcinoma (HCC) patients is understanding how the liver recovers following radiation therapy (RT). While liver regeneration after hepatic resection has been well-studied, liver recovery following RT is less understood. We have previously studied 99mTc-sulphur colloid (SC) single photon emission tomography (SPECT)/CT to spatially and quantitatively analyze liver function. The purpose of this study was to assess both volumetric and functional liver changes following RT.

MATERIALS/METHODS

Patients with HCC had liver function assessed with SC SPECT/CT before and after definitive RT. Patients received 30-67.5 Gy in 4-15 fractions. Anatomic and functional liver metrics were assessed before and after treatment. The anatomic liver volume (ALV) was drawn on CT imaging. Liver function was measured as the functional volume encompassing 30% of maximum uptake (FLV) and mean liver-to-spleen uptake ratio (L/S). Changes in liver size and function were compared to clinical characteristics, including Child-Pugh (CP) score. Parametric t-tests were used to analyze the data.

RESULTS

Of 23 evaluable patients (proton RT, n = 16 or photon RT, n = 7), 15 patients had CP-A5/6, 7 had CP-B7/8, and 1 had CP-C10 scores. The mean interval of SC SPECT was 67 days following RT (range, 44 to 113 days). The mean PTV was 272 cc (range 22-802 cc). Regarding baseline liver status, mean pre-treatment ALV was 1584 cc (range 810-2749 cc) with no significant difference in ALV between CP-A and B/C patients (p = 0.285). Pre-treatment mean liver function as assessed with L/S was 1.06 ± 0.43 with significantly greater function in CP-A compared to CP-B/C patients (1.27 vs 0.66, respectively, p<0.001). Mean pre-treatment FLV was 1351 ± 430.8 cc with no significant difference in FLV between CP-A and B/C patients (1422 ± 441 cc vs 1220 ± 436 cc, respectively, p = 0.31). When evaluating change following RT, the mean change in ALV was 0.9% (range, -29% to 23%) with no significant difference between CP-A and CP-B/C patients (-1.5% vs 5.4%, respectively, p = 0.19). In contrast, change in liver function following RT was larger; mean change in FLV was -20% (range, -55% to 33%) and mean change in L/S was -16% (range, -66% to 105%). While change in FLV was not significantly different between CP-A and CP-B/C patients, CP-B/C patients had significantly greater decline in mean liver function (L/S) than CP-A patients (-40 ± 18% vs -3.6 ± 36%, respectively, p = 0.018). There was no association between change in liver volume and change in L/S, p = 0.543.

CONCLUSION

Functional liver imaging metrics reveal different information about the potential functional reserve of irradiated livers compared to anatomic measurements. These data imply that functional liver imaging may more accurately assess the regenerative potential of irradiated and non-irradiated volumes of liver, which may be useful in clinical scenarios where assessment of the function of future liver remnants become critical.

Cancer-Related Mortality Rates are Lower in U.S. States with Higher GDP per Capita

PURPOSE/OBJECTIVE(S)

Social determinants of health have been established to potentially affect health outcomes more than genetic makeup. Across the US, states have varying age-adjusted cancer-related mortality rates and GDP per capita, but a potential association has not been investigated. The purpose of this study was to assess if cancer-related mortality is related to GDP per capita by state in order to help guide patient advocacy. We hypothesized states with higher GDP per capita more likely had lower cancer-related mortality.

MATERIALS/METHODS

All 50 states were included in this study. Cancer-related mortality rates were collected from the CDC's National Center for Health Statistics National Vital Statistics System. Cancer-related mortality rates were age-adjusted and reported as the number of deaths per 100,000 total people. Nominal GDP per capita was collected from the US Census Bureau's Bureau of Economic Analysis. The most recent data on cancer-related mortality and GDP per capita by state were from 2020 and 2021, respectively. Parametric t-tests and chi-square tests were used to analyze the data. Criteria for statistical significance was p<0.05.

RESULTS

States with a GDP per capita level of ≥ $80K, $70-80K, $60-70K, $50-60K, and < $50K had the following mean cancer-related mortality rates: 137 ± 7.45, 141 ± 7.42, 146 ± 11.0, 153 ± 15.3, and 163 ± 16.4, respectively. States with a GDP per capita ≥ $80K had a mean cancer-related mortality rate significantly less than states with a GDP per capita < $80K (p = 0.03). States with a GDP per capita ≥ $70K had a mean cancer-related mortality rate (139 ± 7.44) significantly less than states with a GDP per capita < $70K (p = 0.003). States with a GDP per capita ≥ $60K had a mean cancer-related mortality rate (142 ± 9.82) significantly less than states with a GDP per capita < $60K (p<0.001). States with a GDP per capita ≥ $50K had a mean cancer-related mortality rate (145 ± 12.5) significantly less than states with a GDP per capita < $50K (p = 0.006). Eleven states were in both the top two quintiles for GDP per capita and in the two most favorable quintiles for cancer-related mortality rate (see Table 1). No state in the top two quintiles for GDP per capita was in the two least favorable quintiles for cancer-related mortality rate. States with a GDP per capita ≥ $80K and ≥ $70K were significantly more likely to have cancer-related mortality rates in the two most favorable quintiles (p = 0.008 and p = 0.004, respectively).

CONCLUSION

Higher state GDP per capita was associated with lower cancer-related mortality rates across the US. Future research should further investigate reasons for this relationship, and oncologists should consider advocating for patients in the sociopolitical realm.

Sustained microglial depletion with CSF1R inhibitor impairs parenchymal plaque development in an Alzheimer's disease model

Many risk genes for the development of Alzheimer's disease (AD) are exclusively or highly expressed in myeloid cells. Microglia are dependent on colony-stimulating factor 1 receptor (CSF1R) signaling for their survival. We designed and synthesized a highly selective brain-penetrant CSF1R inhibitor (PLX5622) allowing for extended and specific microglial elimination, preceding and during pathology development. We find that in the 5xFAD mouse model of AD, plaques fail to form in the parenchymal space following microglial depletion, except in areas containing surviving microglia. Instead, Aβ deposits in cortical blood vessels reminiscent of cerebral amyloid angiopathy. Altered gene expression in the 5xFAD hippocampus is also reversed by the absence of microglia. Transcriptional analyses of the residual plaque-forming microglia show they exhibit a disease-associated microglia profile. Collectively, we describe the structure, formulation, and efficacy of PLX5622, which allows for sustained microglial depletion and identify roles of microglia in initiating plaque pathogenesis.

BRD4 Profiling Identifies Critical Chronic Lymphocytic Leukemia Oncogenic Circuits and Reveals Sensitivity to PLX51107, a Novel Structurally Distinct BET Inhibitor

Bromodomain and extra-terminal (BET) family proteins are key regulators of gene expression in cancer. Herein, we utilize BRD4 profiling to identify critical pathways involved in pathogenesis of chronic lymphocytic leukemia (CLL). BRD4 is overexpressed in CLL and is enriched proximal to genes upregulated or de novo expressed in CLL with known functions in disease pathogenesis and progression. These genes, including key members of the B-cell receptor (BCR) signaling pathway, provide a rationale for this therapeutic approach to identify new targets in alternative types of cancer. Additionally, we describe PLX51107, a structurally distinct BET inhibitor with novel in vitro and in vivo pharmacologic properties that emulates or exceeds the efficacy of BCR signaling agents in preclinical models of CLL. Herein, the discovery of the involvement of BRD4 in the core CLL transcriptional program provides a compelling rationale for clinical investigation of PLX51107 as epigenetic therapy in CLL and application of BRD4 profiling in other cancers.Significance: To date, functional studies of BRD4 in CLL are lacking. Through integrated genomic, functional, and pharmacologic analyses, we uncover the existence of BRD4-regulated core CLL transcriptional programs and present preclinical proof-of-concept studies validating BET inhibition as an epigenetic approach to target BCR signaling in CLL. Cancer Discov; 8(4); 458-77. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 371.

Abstract 4711: Broad anti-tumor activity of a novel BET bromodomain inhibitor

Inhibitors against the bromodomain and extra terminal domain (BET) family of proteins have been pursued as promising oncology agents based on growing understanding of epigenetic control of disease processes. Through scaffold-based and crystallography-guided drug design, we discovered PLX51107, a potent and selective small molecule inhibitor of the BET family bromodomains. PLX51107 is structurally unrelated to the benzodiazepines such as JQ1, I-BET762, and OTX015 and other published BET inhibitors. PLX51107 exhibits low nanomolar potency in blocking interactions mediated by the four BET family proteins BRD2, BRD3, BRD4, and BRDT. Pharmacologic inhibition of BET proteins by PLX51107 suppresses the transcription of genes essential for tumor growth and survival and leads to selective killing of cancer cell lines across a broad range of hematologic malignancies (e.g. leukemia, lymphoma and multiple myeloma). A subset of solid tumors (e.g. melanoma and SCLC) is also sensitive to growth inhibition by the BET inhibitor PLX51107. Novel biomarkers in these diseases have been identified. PLX51107 is well tolerated and has sufficient potency and oral bioavailability to demonstrate in vivo efficacy in animal models of a variety of tumor types, representing both hematologic and solid tumors of diverse genetic backgrounds. In combination studies, PLX51107 showed potential to improve the efficacy (response rates and duration of response) of other anticancer treatments without increased toxicity. These results support further development of PLX51107 as an epigenetic-based therapy for a variety of cancer indications.

Citation Format: Yan Ma, Ben Powell, Jiazhong Zhang, Ying Zhang, Heidi Carias, Ullrich Schwertschlag, Gaston Habets, Prabha Ibrahim, Wayne Spevak, Chao Zhang, Gideon Bollag. Broad anti-tumor activity of a novel BET bromodomain inhibitor. [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 4711.

Vemurafenib: the first drug approved for BRAF-mutant cancer

The identification of driver oncogenes has provided important targets for drugs that can change the landscape of cancer therapies. One such example is the BRAF oncogene, which is found in about half of all melanomas as well as several other cancers. As a druggable kinase, oncogenic BRAF has become a crucial target of small-molecule drug discovery efforts. Following a rapid clinical development path, vemurafenib (Zelboraf; Plexxikon/Roche) was approved for the treatment of BRAF-mutated metastatic melanoma in the United States in August 2011 and the European Union in February 2012. This Review describes the underlying biology of BRAF, the technology used to identify vemurafenib and its clinical development milestones, along with future prospects based on lessons learned during its development.

Abstract 552: Targeting brain tumors with PLX3397, an inhibitor of the CSF-1 receptor kinase

Cancer growth in the brain incites a neuroinflammatory response that becomes a defining feature of the brain tumor microenvironment. Microglia and macrophages provide important functions that support the invasiveness of glioblastoma. Other cancer types that become metastatic to brain also rely on the microenvironment to support angiogenesis.

PLX3397 is a potent inhibitor of the transmembrane tyrosine kinase receptor for colony stimulating factor-1 (CSF-1R). The CSF-1R is required for the differentiation and activation of microglia and macrophages. Oral administration of PLX3397 to mice at 20 mg/kg qd significantly reduces the microglia/macrophage marker, Iba1, as determined by western blotting.

PLX3397 penetrates the blood-brain barrier, as determined through pharmacokinetic analysis, with brain levels reaching substantial fractions of the concurrent plasma levels. PLX3397 is highly bound to plasma albumin, and therefore the levels attained in the brain likely affect Iba1 levels through a local inhibition of brain microglia and macrophages, although a peripheral effect may also contribute.

Culture of glioblastoma cell lines including U87, and treatment with chemotherapeutic agents or radiation, was found to cause a 4-fold elevation of the two CSF-1R ligands, CSF-1 and IL-34, as quantified by QPCR. This indicates that glioma cells can recruit and stimulate microglia and macrophages, and that current standard therapies likely exacerbate this stimulation. Other cancer types that are known to form metastases to brain, including melanoma and breast cancer, show similar abilities to produce these cytokines in response to standard therapies.

The rat 9L glioblastoma line forms an aggressive tumor when tested as an orthotopic model in syngeneic Fisher rats. Seven days after implantation, PLX3397 was administered via rodent chow for 14 days, reducing the tumor growth by 44% as determined by MRI.

These results provide preclinical evidence that PLX3397 may show a clinical benefit in brain cancers, either as a single agent or in combination with standard chemo- or radiation therapies. PLX3397 is nearing completion of a successful Phase 1 dose-escalation safety trial in solid tumor cancer patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 552. doi:10.1158/1538-7445.AM2011-552

Preclinical development of a novel inhibitor of oncogenic B-Raf

13056

Background: The discovery of oncogenic B-Raf mutations in a majority of patients with metastatic melanoma, and in many tumors from patients with colorectal cancer and other cancers, presents the opportunity to develop oncogene-selective inhibitors with a favorable safety profile. Methods: Guided by co-crystallography, a novel chemical scaffold has been developed into a series of potent inhibitors of oncogenic B-Raf with selectivity versus wild-type B-Raf. From this series, a potent inhibitor has been chosen as a candidate for development. Results: Consistent with the structure-guided approach, this compound shows pronounced selectivity versus a wide array of over 70 other kinases covering all branches of the kinome. This selectivity translates to a wide cellular therapeutic index: inhibition of proliferation of a panel of cell lines bearing the V600E oncogenic B-Raf mutation occurs at IC50s ranging from 40–400 nM while inhibition of cell lines lacking oncogenic B-Raf occurs at IC50s greater than 6500 nM. This cell-based selectivity for the oncogenic B-Raf is greater than the selectivity shown in biochemical assays, supporting that tumor cells bearing the oncogenic B-Raf protein are more dependent on the MAP kinase pathway. Combination experiments with a series of cytotoxic and targeted clinical anti-cancer agents reveal multiple examples of synergistic inhibition of proliferation in vitro, and this synergy generally appears selectively in oncogenic B-Raf-bearing cells. The good oral bioavailability (F > 70%) allows for prolonged exposure in both rodents and non-rodents. Robust efficacy is evident in a murine COLO205 tumor xenograft model, with once-daily oral dosing at 20 mg/kg over 14 days resulting in > 80% inhibition of tumor growth with no effect on body weight. Conclusions: Since this compound is highly selective and targets a B-Raf variant that is absent in all non-transformed cells, it may have a broad therapeutic index, alone or in combination, for the treatment of patients with V600E oncogenic B-Raf tumors.

[Table: see text]

Crystal structures of proto-oncogene kinase Pim1: a target of aberrant somatic hypermutations in diffuse large cell lymphoma

Pim1, a serine/threonine kinase, is involved in several biological functions including cell survival, proliferation, and differentiation. While pim1 has been shown to be involved in several hematopoietic cancers, it was also recently identified as a target of aberrant somatic hypermutation in diffuse large cell lymphoma (DLCL), the most common form of non-Hodgkin's lymphoma. The crystal structures of Pim1 in apo form and bound with AMPPNP have been solved and several unique features of Pim1 were identified, including the presence of an extra beta-hairpin in the N-terminal lobe and an unusual conformation of the hinge connecting the two lobes of the enzyme. While the apo Pim1 structure is nearly identical with that reported recently, the structure of AMPPNP bound to Pim1 is significantly different. Pim1 is unique among protein kinases due to the presence of a proline residue at position 123 that precludes the formation of the canonical second hydrogen bond between the hinge backbone and the adenine moiety of ATP. One crystal structure reported here shows that changing P123 to methionine, a common residue that offers the backbone hydrogen bond to ATP, does not restore the ATP binding pocket of Pim1 to that of a typical kinase. These unique structural features in Pim1 result in novel binding modes of AMP and a known kinase inhibitor scaffold, as shown by co-crystallography. In addition, the kinase activities of five Pim1 mutants identified in DLCL patients have been determined. In each case, the observed effects on kinase activity are consistent with the predicted consequences of the mutation on the Pim1 structure. Finally, 70 co-crystal structures of low molecular mass, low-affinity compounds with Pim1 have been solved in order to identify novel chemical classes as potential Pim1 inhibitors. Based on the structural information, opportunities for optimization of one specific example are discussed.

CVT-4325: a potent fatty acid oxidation inhibitor with favorable oral bioavailability

New inhibitors of palmitoyl-CoA oxidation are based on the introduction of nitrogen heterocycles in the 'Western Portion' of the molecule. SAR studies led to the discovery of CVT-4325 (shown), a potent FOXi (IC50=380 nM rat mitochondria) with favorable PK properties (F=93%, t(1/2)=13.6h, dog).

Novel inhibitors of fatty acid oxidation as potential metabolic modulators

We describe the synthesis of novel inhibitors of fatty acid oxidation as potential metabolic modulators for the treatment of stable angina. Replacement of the 2H-benzo[d]1,3-dioxolene ring system in our initial lead 3 with different benzthiazoles, benzoxazoles and introducing small alkyl substituents into the piperazine ring resulted in analogues with enhanced inhibitory activity against 1-(14)[C]-palmitoyl-CoA oxidation in isolated rat heart mitochondria (6, IC(50)=70 nM; 25, IC(50)=23 nM).

Affinity and intrinsic efficacy (IE) of 5′-carbamoyl adenosine analogues for the A1 adenosine receptor—efforts towards the discovery of a chronic ventricular rate control agent for the treatment of atrial fibrillation (AF)

The SAR for the affinity to the A(1) adenosine receptor and relative intrinsic efficacy (IE, [(35)S]-GTPgammaS binding) of a series of 5'-carbamate and 5'-thionocarbamate derivatives of tecadenoson is described. Based on this SAR, selected compounds were evaluated in guinea pig isolated hearts to determine whether they were partial or full agonists with respect to their negative dromotropism, an A(1) AdoR mediated effect. Progress towards obtaining a partial A(1) AdoR agonist to potentially control ventricular rate during atrial fibrillation has been made with the discovery of several potent partial A(1) AdoR agonists (compounds 13, 14, and 17).

Combinatorial synthesis of SSAO inhibitors using sonogashira coupling: SAR of aryl propargylic amines

The structure-activity relationships for semicarbazide-sensitive amine oxidase (SSAO) inhibitors based on arylpropynylamines was investigated using solution-phase combinatorial Sonogashira coupling. The results suggest that binding to the active site occurs by coordination of the amine to the proximal copper(II) and formation of a pi-complex between topaquinone and the electron-rich aryl group of the inhibitor.

Effect of agitation, turbidity, aluminium foil reflectors and container volume on the inactivation efficiency of batch-process solar disinfectors

We report the results of experiments designed to improve the efficacy of the solar disinfection of drinking water, inactivation process. The effects of periodic agitation, covering the rear surface of the container with aluminium foil, container volume and turbidity on the solar inactivation kinetics of Escherichia coli (starting population = 10(6) CFU ml(-1)) were investigated. It was shown that agitation promoted the release of dissolved oxygen from water with subsequent decrease in the inactivation rates of E. coli. In contrast, covering the rear surface of the solar disinfection container with aluminium foil improved the inactivation efficiency of the system. The mean decay constant for bacterial populations in foil-backed bottles was found to be a factor of 1.85 (std. dev. = 0.43) higher than that of non-foil-backed bottles. Inactivation rates decrease as turbidity increases. However, total inactivation was achievable in 300 NTU samples within 8 h exposure to strong sunshine. Inactivation kinetics was not dependent on the volume of the water container for volumes in the range 500-1500 ml.

Potent selective nonpeptidic inhibitors of human lung tryptase

Human lung tryptase, a homotetrameric serine protease unique to mast cell secretory granules, has been implicated in the pathogenesis of asthma. A hypothesis that tethered symmetrical inhibitors might bridge two adjacent active sites was explored via a rationally designed series of bisbenzamidines. These compounds demonstrated a remarkable distanced-defined structure-activity relationship against human tryptase with one series possessing subnanomolar potencies. Additional evidence supporting the concept of active-site bridging is also presented.

SYTO16 labelling and flow cytometry of Mycobacterium avium

Mycobacterium avium cells were harvested from agar at different stages of their growth cycle, exposed to the minimum inhibitory concentration of isoniazid (INH) for 24 h and labelled with the fluorescent nucleic acid stain SYTO16. INH exposure led to a > 10-fold increase in the intensity of labelling in the majority of cells, and revealed discrete fluorescence peaks that were consistent with development of filamentous multinucleate cells during the growth cycle. Similar enhancement of labelling was observed in unfixed INH-treated cells viewed by fluorescence microscopy. INH appears to increase the permeability of Myco. avium cells to SYTO16. A combination of growth cycle-defined inocula, labelling with the new generation of fluorescent dyes and flow cytometry provides new opportunities to study the interrelationships between growth cycle events and antimicrobial susceptibility of mycobacteria.

Comprehension of antibiotic instructions in an outpatient Malaysian practice

Patients may not comply with antibiotic instructions because they do not understand them. The aim of this study was to assess outpatients' ability to comprehend their antibiotic prescription labels. Two hundred and five subjects on oral antibiotic regimens from an outpatient clinic and pharmacy of a district hospital were selected in this survey. All patients were interviewed by trained clinical pharmacy students. They were asked to read the labels and then how they would take their antibiotics. The results show that 119 (58.1%) patients could interpret the label. Forty-nine (23.9%) patients knew the name of antibiotics and interpreted the directions of use correctly. One hundred sixteen (56.6%) subjects were able to recall the auxiliary information. However, only 44 (21.4%) patients were able to comprehend complete antibiotic instruction. This study demonstrates that a significant proportion of patients could not interpret the labeling instruction. The comprehension level of patients was low and significantly associated (P < 0.05) with the ability of patient to read the label contents. These observations illustrate the need for physicians and pharmacists to provide antibiotic instructions and review these instructions with the patient.

A study of patients' self-interpretation of prescription instructions

This study examined out-patients' interpretation of prescription instructions at a community hospital. The results showed a wide range of misinterpretation with respect to drug name, dose schedule, and auxiliary labels. Age level, education and financial status emerged as the most significant variables associated with the patient's response. Therefore, both physicians and pharmacists may wish to review their traditional prescribing and dispensing procedures to help out-patients make better use of potent medication.