ACE2: the molecular doorway to SARS-CoV-2.

The angiotensin-converting enzyme 2 (ACE2) is the host functional receptor for the new virus SARS-CoV-2 causing Coronavirus Disease 2019. ACE2 is expressed in 72 different cell types. Some factors that can affect the expression of the ACE2 are: sex, environment, comorbidities, medications (e.g. anti-hypertensives) and its interaction with other genes of the renin-angiotensin system and other pathways. Different factors can affect the risk of infection of SARS-CoV-2 and determine the severity of the symptoms. The ACE2 enzyme is a negative regulator of RAS expressed in various organ systems. It is with immunity, inflammation, increased coagulopathy, and cardiovascular disease. In this review, we describe the genetic and molecular functions of the ACE2 receptor and its relation with the physiological and pathological conditions to better understand how this receptor is involved in the pathogenesis of COVID-19. In addition, it reviews the different comorbidities that interact with SARS-CoV-2 in which also ACE2 plays an important role. It also describes the different factors that interact with the virus that have an influence in the expression and functional activities of the receptor. The goal is to provide the reader with an understanding of the complexity and importance of this receptor.

Solitary Fibrous Tumors in the Head and Neck: Comprehensive Review and Analysis.

Solitary fibrous tumors (SFT) arising in the head and neck region are uncommon yet well-recognized entities. Their biologic behavior and management still need to be elucidated. Systematically reviewing all published cases of SFT involving the head and neck region since 1991, a pooled meta-analysis was conducted to evaluate various demographic and tumor characteristics. 587 SFT in the head and neck have been reported; 343 met pooled analysis inclusion criteria. 61% of cases presented as a new mass; 89% were painless. Median onset of symptoms prior to evaluation was 8 months. Pre-operative local invasion and malignant histological features (hemorrhage, necrosis, mitoses > 4/10 hpf) were not statistically associated with decreased recurrence-free survival. Positive surgical margins was the only factor associated with shorter recurrence-free survival (p < 0.001). The evidence presented herein reveals novel associations between clinical presentation and tumor characteristics that provide otolaryngologists with new insight into SFT tumor behavior, thus prompting further investigations.

High grade sarcoma, with predominant neuroectodermal and minor embryonal rhabdomyosarcomatous tumor of the uterus: A case report.

BACKGROUND: There have been few documented cases of combined primitive neuroectodermal and embryonal rhabdomyosarcomas (ERMS) in the uterus. Due to their rarity, there is no consensus on the optimal treatment for patients with primitive neuroectodermal tumor (PNET) and ERMS of the uterus. Studies on treatment and outcome are limited. CASE PRESENTATION: A 32 year-old female presented with heavy vaginal bleeding. Ultrasound revealed an 18 cm uterus with thickened endometrium. Histopathology revealed embryonal rhabdomyosarcoma. She underwent a total abdominal hysterectomy, bilateral salpingectomy, lymph node dissection, and omentectomy. Pathologic review confirmed a tumor with mainly central-type PNET and focally ERMS within the uterus and cervix. She was treated with adjuvant chemoradiation. CONCLUSION: Treatment of the predominant tumor, PNET, should be the primary goal of therapy. Vincristine, doxorubicin, cyclophosphamide, ifosfamide, and etoposide with tumor directed radiation may be efficacious for the treatment of this specific high grade uterine sarcoma.

Epithelioid glioblastoma presenting as aphasia in a young adult with ovarian cancer: A case report.

Our patient's clinical history and preoperative radiographic evaluation suggested central nervous system (CNS) metastatic disease. Ultimately, final pathology revealed epithelioid glioblastoma (eGBM), a newly classified CNS primary tumor. This reinforces the importance of direct tissue sampling and including eGBM on the differential for young patients with histories of systemic cancer presenting with new CNS lesions.

Review of inbound medical tourism and legal details of obtaining a visa for treatment of head and neck cancer.

BACKGROUND: We aim to provide a review of inbound medical tourism and the legal process of obtaining a visa for medical/surgical treatment for the patients with head and neck cancer. METHODS: We reviewed current statistics and the medical and legal literature regarding inbound medical tourism and the process of obtaining a visa for patients traveling to the United States for medical treatment. To illustrate this process, we present a case of an advanced-staged and disfiguring facial polymorphous high-grade adenocarcinoma in a previously healthy 29-year-old woman from Liberia. RESULTS: This report provides a synopsis of available statistical data on inbound medical tourism and the legal aspects of obtaining a visa for patients seeking medical care from abroad. CONCLUSIONS: Medical tourists traveling to the United States for treatment of head and neck pathologies face considerable barriers in obtaining prompt care, leading to a possible increased disease burden and difficulty in rendering oncologic treatment.

Cancer immunotherapy using PolyPurine Reverse Hoogsteen hairpins targeting the PD-1/PD-L1 pathway in human tumor cells.

Immunotherapy approaches stand out as innovative strategies to eradicate tumor cells. Among them, PD-1/PD-L1 immunotherapy is considered one of the most successful advances in the history of cancer immunotherapy. We used our technology of Polypurine reverse Hoogsteen hairpins (PPRHs) for silencing both genes with the aim to provoke the elimination of tumor cells by macrophages in co-culture experiments. Incubation of PPRHs against PD-1 and PD-L1 decreased the levels of mRNA and protein in THP-1 monocytes and PC3 prostate cancer cells, respectively. Viability of THP-1 cells and macrophages obtained by PMA-differentiation of THP-1 cells was not affected upon incubation with the different PPRHs. On the other hand, PC3 cell survival was partially decreased by PPRHs against PD-L1. The greatest effect in decreasing cell viability was obtained in macrophages/PC3 co-culture experiments by combining PPRHs against PD-1 and PD-L1. This effect was also observed in other cancer cell lines: HeLa, SKBR3 and to a minor extent in M21. Apoptosis was not detected when macrophages were treated with the different PPRHs. However, co-cultures of macrophages with the four cancer cell lines treated with PPRHs showed an increase in apoptosis. The order of fold-increase in apoptosis was HeLa > PC3 > SKBR3 > M21. This study demonstrates that PPRHs could be powerful pharmacological agents to use in immunotherapy approaches for the inhibition of PD-1 and PD-L1.

Metastatic Renal Cell Carcinoma to Jejunum: An Unusual Case Presentation.

The small intestine is a very uncommon and peculiar site for metastasis from renal cell carcinoma (RCC). We present a clinical presentation of insidious and unusual development of a jejunal metastasis while having stable disease in a remainder of metastatic sites, in a patient undergoing immunotherapy with nivolumab. Due to the extreme rarity of metastatic renal cell carcinoma to the lumen of the small bowel, it is easy to overlook and misdiagnose symptoms of this pathologic entity, particularly when the remainder of metastatic disease responds well to ongoing therapy.

N-ω-chloroacetyl-L-ornithine has in-vitro activity against cancer cell lines and in-vivo activity against ascitic and solid tumors.

N-ω-chloroacetyl-L-ornithine (NCAO) is an ornithine decarboxylase (ODC) inhibitor that is known to exert cytotoxic and antiproliferative effects on three neoplastic human cancer cell lines (HeLa, MCF-7, and HepG2). Here, we show that NCAO has antiproliferative activity in 13 cancer cell lines, of diverse tissue origin from human and mice, and in a mouse cancer model in vivo. All cell lines were sensitive to NCAO after 72 h of treatment (the EC50 ranged from 1 to 50.6 µmol/l). The Ca Ski cell line was the most sensitive (EC50=1.18±0.07 µmol/l) and MDA-MB-231 was the least sensitive (EC50=50.6±0.3 µmol/l). This ODC inhibitor showed selectivity for cancer cells, exerting almost no cytotoxic effect on the normal Vero cell line (EC50>1000 µmol/l). NCAO induced apoptosis and inhibited tumor cell migration in vitro. Furthermore, in vivo, this compound (at 50 and 100 mg/kg, daily intraperitoneal injection for 7 days) exerted potent antitumor activity against both solid and ascitic tumors in a mouse model using the myeloma (Ag8) cell line. At these same two doses, the toxicological evaluation showed that NCAO has no obvious systemic toxicity. The current results suggest that the antitumor activity is exerted by apoptosis related not only to a local but also a systemic cytotoxic effect exerted by NCAO on tumor cells. The applications for NCAO as an antitumor agent may be extensive; however, further studies are needed to ascertain the antitumor activity on other types of tumor in vivo and to determine the precise molecular mechanism of its activity.

Non-radiative relaxation of photoexcited chlorophylls: theoretical and experimental study.

Nonradiative relaxation of high-energy excited states to the lowest excited state in chlorophylls marks the first step in the process of photosynthesis. We perform ultrafast transient absorption spectroscopy measurements, that reveal this internal conversion dynamics to be slightly slower in chlorophyll B than in chlorophyll A. Modeling this process with non-adiabatic excited state molecular dynamics simulations uncovers a critical role played by the different side groups in the two molecules in governing the intramolecular redistribution of excited state wavefunction, leading, in turn, to different time-scales. Even given smaller electron-vibrational couplings compared to common organic conjugated chromophores, these molecules are able to efficiently dissipate about 1 eV of electronic energy into heat on the timescale of around 200 fs. This is achieved via selective participation of specific atomic groups and complex global migration of the wavefunction from the outer to inner ring, which may have important implications for biological light-harvesting function.

Energy transfer dynamics in trimers and aggregates of light-harvesting complex II probed by 2D electronic spectroscopy.

The pathways and dynamics of excitation energy transfer between the chlorophyll (Chl) domains in solubilized trimeric and aggregated light-harvesting complex II (LHCII) are examined using two-dimensional electronic spectroscopy (2DES). The LHCII trimers and aggregates exhibit the unquenched and quenched excitonic states of Chl a, respectively. 2DES allows direct correlation of excitation and emission energies of coupled states over population time delays, hence enabling mapping of the energy flow between Chls. By the excitation of the entire Chl b Qy band, energy transfer from Chl b to Chl a states is monitored in the LHCII trimers and aggregates. Global analysis of the two-dimensional (2D) spectra reveals that energy transfer from Chl b to Chl a occurs on fast and slow time scales of 240-270 fs and 2.8 ps for both forms of LHCII. 2D decay-associated spectra resulting from the global analysis identify the correlation between Chl states involved in the energy transfer and decay at a given lifetime. The contribution of singlet-singlet annihilation on the kinetics of Chl energy transfer and decay is also modelled and discussed. The results show a marked change in the energy transfer kinetics in the time range of a few picoseconds. Owing to slow energy equilibration processes, long-lived intermediate Chl a states are present in solubilized trimers, while in aggregates, the population decay of these excited states is significantly accelerated, suggesting that, overall, the energy transfer within the LHCII complexes is faster in the aggregated state.

N-ω-chloroacetyl-l-ornithine, a new competitive inhibitor of ornithine decarboxylase, induces selective growth inhibition and cytotoxicity on human cancer cells versus normal cells.

Many cancer cells have high expression of ornithine decarboxylase (ODC) and there is a concerted effort to seek new inhibitors of this enzyme. The aim of the study was to initially characterize the inhibition properties, then to evaluate the cytotoxicity/antiproliferative cell based activity of N-ω-chloroacetyl-l-ornithine (NCAO) on three human cancer cell lines. Results showed NCAO to be a reversible competitive ODC inhibitor (Ki = 59 µM) with cytotoxic and antiproliferative effects, which were concentration- and time-dependent. The EC50,72h of NCAO was 15.8, 17.5 and 10.1 µM for HeLa, MCF-7 and HepG2 cells, respectively. NCAO at 500 µM completely inhibited growth of all cancer cells at 48 h treatment, with almost no effect on normal cells. Putrescine reversed NCAO effects on MCF-7 and HeLa cells, indicating that this antiproliferative activity is due to ODC inhibition.

Effect of protein aggregation on the spectroscopic properties and excited state kinetics of the LHCII pigment­protein complex from green plants.

Steady-state and time-resolved absorption and fluorescence spectroscopic experiments have been carried out at room and cryogenic temperatures on aggregated and unaggregated monomeric and trimeric LHCII complexes isolated from spinach chloroplasts. Protein aggregation has been hypothesized to be one of the mechanistic factors controlling the dissipation of excess photo-excited state energy of chlorophyll during the process known as nonphotochemical quenching. The data obtained from the present experiments reveal the role of protein aggregation on the spectroscopic properties and dynamics of energy transfer and excited state deactivation of the protein-bound chlorophyll and carotenoid pigments.

Temperature and carbon assimilation regulate the chlorosome biogenesis in green sulfur bacteria.

Green photosynthetic bacteria adjust the structure and functionality of the chlorosome-the light-absorbing antenna complex-in response to environmental stress factors. The chlorosome is a natural self-assembled aggregate of bacteriochlorophyll (BChl) molecules. In this study, we report the regulation of the biogenesis of the Chlorobaculum tepidum chlorosome by carbon assimilation in conjunction with temperature changes. Our studies indicate that the carbon source and thermal stress culture of C. tepidum grows slower and incorporates fewer BChl c in the chlorosome. Compared with the chlorosome from other cultural conditions we investigated, the chlorosome from the carbon source and thermal stress culture displays (a) smaller cross-sectional radius and overall size, (b) simplified BChl c homologs with smaller side chains, (c) blue-shifted Qy absorption maxima, and (d) a sigmoid-shaped circular dichroism spectra. Using a theoretical model, we analyze how the observed spectral modifications can be associated with structural changes of BChl aggregates inside the chlorosome. Our report suggests a mechanism of metabolic regulation for chlorosome biogenesis.

The nature of the intramolecular charge transfer state in peridinin.

Experimental and theoretical evidence is presented that supports the theory that the intramolecular charge transfer (ICT) state of peridinin is an evolved state formed via excited-state bond-order reversal and solvent reorganization in polar media. The ICT state evolves in <100 fs and is characterized by a large dipole moment (~35 D). The charge transfer character involves a shift of electron density within the polyene chain, and it does not involve participation of molecular orbitals localized in either of the ß-rings. Charge is moved from the allenic side of the polyene into the furanic ring region and is accompanied by bond-order reversal in the central portion of the polyene chain. The electronic properties of the ICT state are generated via mixing of the "1(1)Bu(+)" ionic state and the lowest-lying "2(1)Ag(-)" covalent state. The resulting ICT state is primarily (1)Bu(+)-like in character and exhibits not only a large oscillator strength but an unusually large doubly excited character. In most solvents, two populations exist in equilibrium, one with a lowest-lying ICT ionic state and a second with a lowest-lying "2(1)Ag(-)" covalent state. The two populations are separated by a small barrier associated with solvent relaxation and cavity formation.

Energetics and dynamics of the low-lying electronic states of constrained polyenes: implications for infinite polyenes.

Steady-state and ultrafast transient absorption spectra were obtained for a series of conformationally constrained, isomerically pure polyenes with 5-23 conjugated double bonds (N). These data and fluorescence spectra of the shorter polyenes reveal the N dependence of the energies of six (1)B(u)(+) and two (1)A(g)(-) excited states. The (1)B(u)(+) states converge to a common infinite polyene limit of 15,900 ± 100 cm(-1). The two excited (1)A(g)(-) states, however, exhibit a large (~9000 cm(-1)) energy difference in the infinite polyene limit, in contrast to the common value previously predicted by theory. EOM-CCSD ab initio and MNDO-PSDCI semiempirical MO theories account for the experimental transition energies and intensities. The complex, multistep dynamics of the 1(1)B(u)(+) → 2(1)A(g)(-) → 1(1)A(g)(-) excited state decay pathways as a function of N are compared with kinetic data from several natural and synthetic carotenoids. Distinctive transient absorption signals in the visible region, previously identified with S* states in carotenoids, also are observed for the longer polyenes. Analysis of the lifetimes of the 2(1)A(g)(-) states, using the energy gap law for nonradiative decay, reveals remarkable similarities in the N dependence of the 2(1)A(g)(-) decay kinetics of the carotenoid and polyene systems. These findings are important for understanding the mechanisms by which carotenoids carry out their roles as light-harvesting molecules and photoprotective agents in biological systems.

Effect of Molecular Symmetry on the Spectra and Dynamics of the Intramolecular Charge Transfer (ICT) state of peridinin.

The spectroscopic properties and dynamics of the excited states of two different synthetic analogues of peridinin were investigated as a function of solvent polarity using steady-state absorption, fluorescence, and ultrafast time-resolved optical spectroscopy. The analogues are denoted S-1- and S-2-peridinin and differ from naturally occurring peridinin in the location of the lactone ring and its associated carbonyl group, known to be obligatory for the observation of a solvent dependence of the lifetime of the S(1) state of carotenoids. Relative to peridinin, S-1- and S-2-peridinin have their lactone rings two and four carbons more toward the center of the π-electron system of conjugated carbon-carbon double bonds, respectively. The present experimental results show that as the polarity of the solvent increases, the steady-state spectra of the molecules broaden, and the lowest excited state lifetime of S-1-peridinin changes from ∼155 to ∼17 ps which is similar to the magnitude of the effect reported for peridinin. The solvent-induced change in the lowest excited state lifetime of S-2-peridinin is much smaller and changes only from ∼90 to ∼67 ps as the solvent polarity is increased. These results are interpreted in terms of an intramolecular charge transfer (ICT) state that is formed readily in peridinin and S-1-peridinin, but not in S-2-peridinin. Quantum mechanical computations reveal the critical factors required for the formation of the ICT state and the associated solvent-modulated effects on the spectra and dynamics of these molecules and other carbonyl-containing carotenoids and polyenes. The factors are the magnitude and orientation of the ground- and excited-state dipole moments which must be suitable to generate sufficient mixing of the lowest two excited singlet states.

The use of immunohistochemical expression of SF-1 and EMA in distinguishing adrenocortical tumors from renal neoplasms.

Steroidogenic factor -1 (SF-1) is an orphan member of the nuclear hormone receptor superfamily, and is considered to play an important role in the differentiation of steroidogenic tissues. In this study, we compared the immunohistochemical stains of SF-1 and epithelial membrane antigen (EMA) in non-neoplastic adrenal tissue, and adrenal and renal tumors using tissue microarrays (TMAs). The adrenal tissue array included 19 cases of normal adrenal cortex, 22 cases of adrenal adenoma, and 20 cases of adrenal cortical carcinoma. The renal tissue array included 20 cases of each of the following types of renal cell carcinoma: clear cell, papillary, and chromophobe. In addition, 20 cases of renal oncocytoma were also included in the study. SF-1 showed positive staining in all cases (100%) of normal adrenal cortex and adrenal cortical adenoma, and in 18 (90%) cases of adrenocortical carcinoma. In renal tumors, SF-1 showed negative stains in all of oncocytoma, papillary, and chromophobe renal cell carcinoma. Only 3 out of 20 cases of clear cell renal cell carcinoma showed weak positivity in approximately 10% of tumor cells. EMA stained positively in 85%, 95%, 100%, and 95% of clear cell, papillary, chromophobe renal cell carcinomas, and oncocytomas, respectively. EMA was completely negative in the adrenal TMAs. In conclusion, SF-1 and EMA may be helpful in the differentiation of adrenal tumors from renal tumors in difficult cases.

CDX2 expression in columnar cell variant of papillary thyroid carcinoma.

The columnar cell variant of papillary thyroid carcinoma (CCV-PTC) is a rare subtype of PTC that exhibits morphologic features often described as reminiscent of secretory endometrium or colonic adenomas/adenocarcinomas. CDX2, a nuclear transcription factor, is important for intestinal development. It is normally expressed in intestinal epithelium and is also detected in adenoma and adenocarcinomas of the gastrointestinal tract; however, it has also been reported in tumors of other sites with intestinal-type morphologic features. We evaluated CDX2 expression in CCV-PTC and in a thyroid tissue microarray composed of various benign and malignant thyroid lesions. CDX2 expression was identified in 6 (55%) of 11 cases of CCV-PTC, but not in any other benign and malignant thyroid lesions. We conclude that CDX2 is selectively expressed in CCV-PTC and can be used in distinguishing it from other variants of PTC with overlapping morphologic features.

Role of xanthophylls in light harvesting in green plants: a spectroscopic investigation of mutant LHCII and Lhcb pigment-protein complexes.

The spectroscopic properties and energy transfer dynamics of the protein-bound chlorophylls and xanthophylls in monomeric, major LHCII complexes, and minor Lhcb complexes from genetically altered Arabidopsis thaliana plants have been investigated using both steady-state and time-resolved absorption and fluorescence spectroscopic methods. The pigment-protein complexes that were studied contain Chl a, Chl b, and variable amounts of the xanthophylls, zeaxanthin (Z), violaxanthin (V), neoxanthin (N), and lutein (L). The complexes were derived from mutants of plants denoted npq1 (NVL), npq2lut2 (Z), aba4npq1lut2 (V), aba4npq1 (VL), npq1lut2 (NV), and npq2 (LZ). The data reveal specific singlet energy transfer routes and excited state spectra and dynamics that depend on the xanthophyll present in the complex.

Singlet and triplet state spectra and dynamics of structurally modified peridinins.

The peridinin-chlorophyll a-protein (PCP) is a light-harvesting pigment-protein complex found in many species of marine algae. It contains the highly substituted carotenoid peridinin and chlorophyll a, which together facilitate the transfer of absorbed solar energy to the photosynthetic reaction center. Photoexcited peridinin exhibits unorthodox spectroscopic and kinetic behavior for a carotenoid, including a strong dependence of the S(1) excited singlet state lifetime on solvent environment. This effect has been attributed to the presence of an intramolecular charge transfer (ICT) state in the molecule. The present work explores the effect of changing the extent of π-electron conjugation and attached functional groups on the nature of the ICT state of peridinin and how these factors affect the excited singlet and triplet state spectra and kinetics of the carotenoid. In this investigation three peridinin analogues denoted C-1-R-peridinin, C-1-peridinin, and D-1-peridinin were synthesized and studied using steady-state absorption and fluorescence techniques and ultrafast time-resolved transient absorption spectroscopy. The study explores the effect on the singlet and triplet state spectra and dynamics of removing the allene group from the peridinin structure and either replacing it with a rigid furanoid ring, replacing it with an epoxide group, or extending the polyene chain into the ß-ionylidine ring.