An optical neural chip for implementing complex-valued neural network

Complex-valued neural networks have many advantages over their real-valued counterparts. Conventional digital electronic computing platforms are incapable of executing truly complex-valued representations and operations. In contrast, optical computing platforms that encode information in both phase and magnitude can execute complex arithmetic by optical interference, offering significantly enhanced computational speed and energy efficiency. However, to date, most demonstrations of optical neural networks still only utilize conventional real-valued frameworks that are designed for digital computers, forfeiting many of the advantages of optical computing such as efficient complex-valued operations. In this article, we highlight an optical neural chip (ONC) that implements truly complex-valued neural networks. We benchmark the performance of our complex-valued ONC in four settings: simple Boolean tasks, species classification of an Iris dataset, classifying nonlinear datasets (Circle and Spiral), and handwriting recognition. Strong learning capabilities (i.e., high accuracy, fast convergence and the capability to construct nonlinear decision boundaries) are achieved by our complex-valued ONC compared to its real-valued counterpart.

Esophageal squamous cell carcinoma (ESCC): advance in genomics and molecular genetics

Esophageal cancer is aggressive and has poor prognosis. Esophageal squamous cell carcinoma (ESCC) is histologically the most prevalent type of esophageal cancer and ranked as the sixth leading cause of cancer death worldwide. In recent years, cancer has been widely regarded as genetic disease, as well as epigenetic abnormalities including DNA methylation, histone deacetylation, chromatin remodeling, gene imprinting and noncoding RNA regulation. In this review, we will provide a general overview of genes, proteins and microRNAs that are involved in the development of ESCC, which aims to enhance our understanding of molecular mechanisms implicated in ESCC development and progression.

Design of an ultra-compact electro-absorption modulator comprised of a deposited TiN/HfO₂/ITO/Cu stack for CMOS backend integration

An ultra-compact electro-absorption (EA) modulator operating around 1.55-μm telecom wavelengths is proposed and theoretically investigated. The modulator is comprised of a stack of TiN/HfO2</ITO/Cu conformally deposited on a single-mode stripe waveguide to form a hybrid plasmonic waveguide (HPW). Since the thin ITO layer can behave as a semiconductor, the stack itself forms a MOS capacitor. A voltage is applied between the Cu and TiN layers to change the electron concentration of ITO (NITO), which in turn changes its permittivity as well as the propagation loss of HPW. For a HPW comprised of a Cu/3-nm-ITO/5-nm-HfO2/5-nm-TiN stack on a 400-nm × 340-nm-Si stripe waveguide, the propagation loss for the 1.55-μm TE (TM) mode increases from 1.6 (1.4) to 23.2 (23.9) dB/μm when the average NITO in the 3-nm ITO layer increases from 2 × 10(20) to 7 × 10(20) cm(-3), which is achieved by varying the voltage from -2 to 4 V if the initial NITO is 3.5 × 10(20) cm(-3). As a result, a 1-μm-long EA modulator inserted in the 400-nm × 340-nm-Si stripe waveguide exhibits insertion loss of 2.9 (3.2) dB and modulation depth of 19.9 (15.2) dB for the TE (TM) mode. The modulation speed is ~11 GHz, limited by the RC delay, and the energy consumption is ~0.4 pJ/bit. The stack can also be deposited on a low-index-contrast waveguide such as Si3N4. For example, a 4-μm-long EA modulator inserted in an 800-nm × 600-nm-Si3N4 stripe waveguide exhibits insertion loss of 6.3 (3.5) dB and modulation depth of 16.5 (15.8) dB for the TE (TM) mode. The influences of the ITO, TiN, HfO2 layers and the beneath dielectric core, as well as the processing tolerance, on the performance of the proposed EA modulator are systematically investigated.

SAA1 polymorphisms are associated with variation in antiangiogenic and tumor-suppressive activities in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a cancer that occurs in high frequency in Southern China. A previous functional complementation approach and the subsequent cDNA microarray analysis have identified that serum amyloid A1 (SAA1) is an NPC candidate tumor suppressor gene. SAA1 belongs to a family of acute-phase proteins that are encoded by five polymorphic coding alleles. The SAA1 genotyping results showed that only three SAA1 isoforms (SAA1.1, 1.3 and 1.5) were observed in both Hong Kong NPC patients and healthy individuals. This study aims to determine the functional role of SAA1 polymorphisms in tumor progression and to investigate the relationship between SAA1 polymorphisms and NPC risk. Indeed, we have shown that restoration of SAA1.1 and 1.3 in the SAA1-deficient NPC cell lines could suppress tumor formation and angiogenesis in vitro and in vivo. The secreted SAA1.1 and SAA1.3 proteins can block cell adhesion and induce apoptosis in the vascular endothelial cells. In contrast, the SAA1.5 cannot induce apoptosis or inhibit angiogenesis because of its weaker binding affinity to αVβ3 integrin. This can explain why SAA1.5 has no tumor-suppressive effects. Furthermore, the NPC tumors with this particular SAA1.5/1.5 genotype showed higher levels of SAA1 gene expression, and SAA1.1 and 1.3 alleles were preferentially inactivated in tumor tissues that were examined. These findings further strengthen the conclusion for the defective function of SAA1.5 in suppression of tumor formation and angiogenesis. Interestingly, the frequency of the SAA1.5/1.5 genotype in NPC patients was ~2-fold higher than in the healthy individuals (P=0.00128, odds ratio=2.28), which indicates that this SAA1 genotype is significantly associated with a higher NPC risk. Collectively, this homozygous SAA1.5/1.5 genotype appears to be a recessive susceptibility gene, which has lost the antiangiogenic function, whereas SAA1.1 and SAA1.3 are the dominant alleles of the tumor suppressor phenotype.

Silicon nitride based plasmonic components for CMOS back-end-of-line integration

Silicon nitride waveguides provide low propagation loss but weak mode confinement due to the relatively small refractive index contrast between the Si₃N₄ core and the SiO2 cladding. On the other hand, metal-insulator-metal (MIM) plasmonic waveguides offer strong mode confinement but large propagation loss. In this work, MIM-like plasmonic waveguides and passive devices based on horizontal Cu-Si₃N₄-Cu or Cu-SiO₂-Si₃N₄-SiO₂-Cu structures are integrated in the conventional Si₃N₄ waveguide circuits using standard CMOS backend processes, and are characterized around 1550-nm telecom wavelengths using the conventional fiber-waveguide-fiber method. The Cu-Si₃N₄(~100 nm)-Cu devices exhibit ~0.78-dB/μm propagation loss for straight waveguides, ~38% coupling efficiency with the conventional 1-μm-wide Si₃N₄ waveguide through a 2-μm-long taper coupler, ~0.2-dB bending loss for sharp 90° bends, and ~0.1-dB excess loss for ultracompact 1 × 2 and 1 × 4 power splitters. Inserting a ~10-nm SiO₂ layer between the Si3N4 core and the Cu cover (i.e., the Cu-SiO2(~10 nm)-Si₃N₄(~100 nm)-SiO2(~10 nm)-Cu devices), the propagation loss and the coupling efficiency are improved to ~0.37 dB/μm and ~52% while the bending loss and the excess loss are degraded to ~3.2 dB and ~2.1 dB, respectively. These experimental results are roughly consistent with the numerical simulation results after taking the influence of possible imperfect fabrication into account. Ultracompact plasmonic ring resonators with 1-μm radius are demonstrated with an extinction ratio of ~18 dB and a quality factor of ~84, close to the theoretical prediction.

Microelectromechanical Maltese-cross metamaterial with tunable terahertz anisotropy

Dichroic polarizers and waveplates exploiting anisotropic materials have vast applications in displays and numerous optical components, such as filters, beamsplitters and isolators. Artificial anisotropic media were recently suggested for the realization of negative refraction, cloaking, hyperlenses, and controlling luminescence. However, extending these applications into the terahertz domain is hampered by a lack of natural anisotropic media, while artificial metamaterials offer a strong engineered anisotropic response. Here we demonstrate a terahertz metamaterial with anisotropy tunable from positive to negative values. It is based on the Maltese-cross pattern, where anisotropy is induced by breaking the four-fold symmetry of the cross by displacing one of its beams. The symmetry breaking permits the excitation of a Fano mode active for one of the polarization eigenstates controlled by actuators using microelectromechanical systems. The metamaterial offers new opportunities for the development of terahertz variable waveplates, tunable filters and polarimetry.

Theoretical investigation of ultracompact and athermal Si electro-optic modulator based on Cu-TiO2-Si hybrid plasmonic donut resonator

An ultracompact silicon electro-optic modulator operating at 1550-nm telecom wavelengths is proposed and analyzed theoretically, which consists of a Cu-TiO(2)-Si hybrid plasmonic donut resonator evanescently coupled with a conventional Si channel waveguide. Owing to a negative thermo-optic coefficient of TiO(2) (~-1.8 × 10(-4) K(-1)), the real part of effective modal index of the curved Cu-TiO(2)-Si hybrid waveguide can be temperature-independent (i.e., athermal) if the TiO(2) interlayer and the beneath Si core have a certain thickness ratio. A voltage applied between the ring-shaped Cu cap and a cylinder metal electrode positioned at the center of the donut,--which makes Ohmic contact to Si, induces a ~1-nm-thick free-electron accumulation layer at the TiO(2)/Si interface. The optical field intensity in this thin accumulation layer is significantly enhanced if the accumulation concentration is sufficiently large (i.e., > ~6 × 10(20) cm(-3)), which in turn modulates both the resonance wavelengths and the extinction ratio of the donut resonator simultaneously. For a modulator with the total footprint inclusive electrodes of ~8.6 μm(2), 50-nm-thick TiO(2), and 160-nm-thick Si core, FDTD simulation predicts that it has an insertion loss of ~2 dB, a modulation depth of ~8 dB at a voltage swing of ~6 V, a speed-of-response of ~35 GHz, and a switching energy of ~0.45 pJ/bit, and it is athermal around room temperature. The modulator's performances can be further improved by optimization of the coupling strength between the bus waveguide and the donut resonator.

Phase modulation in horizontal metal-insulator-silicon-insulator-metal plasmonic waveguides

An extremely compact Si phase modulator is proposed and validated, which relies on effective modulation of the real part of modal index of horizontal metal-insulator-Si-insulator-metal plasmonic waveguides by a voltage applied between the metal cover and the Si core. Proof-of-concept devices are fabricated on silicon-on-insulator substrates using standard complementary metal-oxide-semiconductor technology using copper as the metal and thermal silicon dioxide as the insulator. A modulator with a 1-μm-long phase shifter inserted in an asymmetric Si Mach-Zehnder interferometer exhibits 9-dB extinction ratio under a 6-V/10-kHz voltage swing. Numerical simulations suggest that high speed and low driving voltage could be achieved by shortening the distance between the Si core and the n(+)-contact and by using a high-κ dielectric as the insulator, respectively.

Performance of ultracompact copper-capped silicon hybrid plasmonic waveguide-ring resonators at telecom wavelengths

Ultracompact Cu-capped Si hybrid plasmonic waveguide-ring resonators (WRRs) with ring radii of 1.09-2.59 μm are fabricated on silicon on insulator substrates using standard complementary metal-oxide-semiconductor technology and characterized over the telecom wavelength range of 1.52-1.62 μm. The dependence of the spectral characteristics on the key structural parameters such as the Si core width, the ring radius, the separation gap between the ring and bus waveguides, and the ring configuration is systematically studied. A WRR with 2.59-μm radius and 0.250-μm nominal gap exhibits good performances such as normalized insertion loss of ~0.1 dB, extinction ratio of ~12.8 dB, free spectral range of ~47 nm, and quality factor of ~275. The resonance wavelength is redshifted by ~4.6 nm and an extinction ratio of ~7.5 dB is achieved with temperature increasing from 27 to 82°C. The corresponding effective thermo-optical coefficient (dn(g)/dT) is estimated to be ~1.6 × 10(-4) K(-1), which is contributed by the thermo-optical effect of both the Si core and the Cu cap, as revealed by numerical simulations. Combined with the compact size and the high thermal conductivity of Cu, various effective thermo-optical devices based on these Cu-capped plasmonic WRRs could be realized for seamless integration in existing Si electronic-photonic integrated circuits.

A nano-opto-mechanical pressure sensor via ring resonator

This paper reports a nano-opto-mechanical pressure sensor based on nano-scaled ring resonator. The pressure is measured through the output spectrum shift which is induced via mechanical deformation of the ring resonator. The sensitivity as high as 1.47 pm/kPa has been experimentally achieved which agrees with numerical prediction. Due to the strong variation of sensitivity with different ring radius and thickness of the diaphragm, the pressure sensor can be used to form an array structure to detect the pressure distribution in highly accurate measurement with low-cost advantages. The nano-opto-mechanical pressure sensor has potential applications such as shear stress displacement detection, pressure wave detector and pressure mapping etc.

Components for silicon plasmonic nanocircuits based on horizontal Cu-SiO₂-Si-SiO₂-Cu nanoplasmonic waveguides

We report systematic results on the development of horizontal Cu-SiO₂-Si-SiO₂-Cu nanoplasmonic waveguide components operating at 1550-nm telecom wavelengths, including straight waveguides, sharp 90° bends, power splitters, and Mach-Zehnder interferometers (MZIs). Owing to the relatively low loss for propagating (~0.3 dB/µm) and for 90° sharply bending (~0.73 dB/turn), various ultracompact power splitters and MZIs are experimentally realized on a silicon-on-insulator (SOI) platform using standard CMOS technology. The demonstrated splitters exhibit a relatively low excess loss and the MZIs exhibit good performance such as high extinction ratio of ~18 dB and low normalized insertion loss of ~1.7 dB. The experimental results of these devices agree well with those predicted from numerical simulations with suitable Cu permittivity data.

Theoretical investigation of silicide Schottky barrier detector integrated in horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguide

An ultracompact integrated silicide Schottky barrier detector (SBD) is designed and theoretically investigated to electrically detect the surface plasmon polariton (SPP) propagating along horizontal metal-insulator-silicon-insulator-metal nanoplasmonic slot waveguides at the telecommunication wavelength of 1550 nm. An ultrathin silicide layer inserted between the silicon core and the insulator, which can be fabricated precisely using the well-developed self-aligned silicide process, absorbs the SPP power effectively if a suitable silicide is chosen. Moreover, the Schottky barrier height in the silicide-silicon-silicide configuration can be tuned substantially by the external voltage through the Schottky effect owing to the very narrow silicon core. For a TaSi(2) detector with optimized dimensions, numerical simulation predicts responsivity of ~0.07 A/W, speed of ~60 GHz, dark current of ~66 nA at room temperature, and minimum detectable power of ~-29 dBm. The design also suggests that the device's size can be reduced and the overall performances will be further improved if a silicide with smaller permittivity is used.

Silicon-based horizontal nanoplasmonic slot waveguides for on-chip integration

Horizontal metal/insulator/Si/insulator/metal nanoplasmonic slot waveguide (PWG), which is inserted in a conventional Si wire waveguide, is fabricated using the standard Si-CMOS technology. A thin insulator between the metal and the Si core plays a key role: it not only increases the propagation distance as the theoretical prediction, but also prevents metal diffusion and/or metal-Si reaction. Cu-PWGs with the Si core width of ~134-21 nm and ~12-nm-thick SiO2 on each side exhibit a relatively low propagation loss of ~0.37-0.63 dB/µm around the telecommunication wavelength of 1550 nm, which is ~2.6 times smaller than the Al-counterparts. A simple tapered coupler can provide an effective coupling between the PWG and the conventional Si wire waveguide. The coupling efficiency as high as ~0.1-0.4 dB per facet is measured. The PWG allows a sharp bending. The pure bending loss of a Cu-PWG direct 90° bend is measured to be ~0.6-1.0 dB. These results indicate the potential for seamless integration of various functional nanoplasmonic devices in existing Si electronic photonic integrated circuits (Si-EPICs).

Comparison of the Density and Distribution of Traps Generated by High Voltage Stress in Silicon Oxide and Silicon Oxynitrides

A technique has been developed to determine the density and distribution of spatially deep traps throughout an insulator. These traps were created and charged by a high voltage stressing pulse and allowed to discharge upon the removal of the pulse. During the transient following pulse removal, the currents were measured. A correlation from current to trap densities and from time of decay to location within the dielectric has been made. This method has been applied to gauge the differences between nitrided dielectrics and thermal oxides. We have found initial trap levels, before stressing, to be lower in silicon oxide devices than silicon oxynitride devices. However, trap levels increased faster in thermal oxides as the stress increased, and became larger than the levels found in nitrided oxides. Nitrided devices tended to resist additional trap formation. Current-voltage measurements have shown that nitrides developed higher leakage currents as the stress was increased than did thermal oxides.

Photoluminescence and Structure of Chemically Etched Si

We demonstrate for the first time that chemical etching of Si in HF-HNO3-based solution without applying bias can produce a room temperature photoluminescent porous Si layer. Scanning electron microscope studies reveal a surface morphology similar to that of the conventionally anodized porous Si. The formation mechanism of the chemically etched (CE) film can be explained by a local anodization concept. X-ray diffraction studies on the luminescent CE porous Si show a broad amorphous peak.

Study of Thermal Stability of Cvd Ta205/Si Interface

The effects of vacuum and inert gas annealing of ultra-thin (20Å) CVD Ta2O5 films deposited on Si substrates, with and without oxynitride interface layer, on the Ta2O5/Si interface stability were examined extensively by means of in-situ X-ray Photoelectron Spectroscopy (XPS), ex-situ Time-of-Flight Secondary Ion mass Spectrometry (ToF-SIMS), and Temperature Programmed Reaction (TPR). When annealed to 680 °C for up to 50 min, changes in ∼ 20Å Ta2O5 films formed on Si(100) are negligible, but annealing to 820 °C for 10 min in vacuum, Ar or N2 produces major chemical restructuring. SiO is formed at the Ta2O5 - Si(100) interfaces and becomes incorporated into the tantalum oxide. A reduced form of Ta, attributed to TaSix, forms at the buried interface. Extending the annealing time to 20 min produces no further changes. SiO desorbs during annealing at 1000 °C. Nitriding Si prior to forming the Ta2O5 film deposition inhibits these processes.

Theoretical investigation of silicon MOS-type plasmonic slot waveguide based MZI modulators

In this paper, a Mach-Zehnder silicon nanoplasmonic electro-optic modulator is proposed and theoretically analyzed. It is composed of horizontal metal-SiO2-Si-metal plasmonic slot waveguides for phase shifting and ultracompact V-shape splitter/combiner to link the plasmonic slot waveguides and the conventional Si dielectric waveguides. The proposed modulator can be directly integrated into existing Si electronic photonic integrated circuits (EPICs) and be fabricated using standard Si complementary metal-oxide-semiconductor (CMOS) technology. The modulator's parameters are optimized through systematic 2-dimensional numerical simulations. For a modulator with 3-µm-long Ag-SiO2(2 nm)-Si(50 nm)-Ag phase shifter and 0.35-µm-long splitter/combiner operating at 1.55-µm wavelength, simulation shows an insertion loss of ~-8 dB, an extinction ratio of ~7.3 dB - with a switching voltage of ~5.6 V, and a bandwidth of ~500 GHz. A possible approach to reduce the switching voltage is addressed.

Low-loss amorphous silicon wire waveguide for integrated photonics: effect of fabrication process and the thermal stability

Hydrogenated amorphous silicon (a-Si:H) wire waveguides were fabricated by plasma-enhanced chemical vapor deposition and anisotropic dry etching. With the optimized fabrication process, the propagation losses of as low as 3.2 ± 0.2 dB/cm for the TE mode and 2.3 ± 0.1 dB/cm for the TM mode were measured for the 200 nm (height) × 500 nm (width) wire waveguides at 1550 nm using the standard cutback method. The loss becomes larger at shorter wavelength (~4.4 dB/cm for TE and ~5.0 dB/cm for TM at 1520 nm) and smaller at longer wavelength (~1.9 dB/cm for TE and ~1.4 dB/cm for TM at 1620 nm). With the waveguide width shrinking from 500 nm to 300 nm, the TM mode loss keeps almost unchanged whereas the TE mode loss increases, indicating that the predominant loss contributor is the waveguide sidewall roughness, similar to the crystalline silicon waveguides. Although the a-Si:H and the upper cladding SiO2 were both deposited at 400°C, the propagation loss of the fabricated a-Si:H wire waveguides starts to increase upon furnace annealing under atmosphere at a temperature larger than 300°C: ~13-15 dB/cm after 400°C/30 min annealing and >70 dB/cm after 500°C/30 min annealing, which can be attributed to hydrogen out-diffusion. Even higher temperature (i.e., >600°C) annealing leads to the propagation loss approaching to the polycrystalline silicon counterparts (~40-50 dB/cm) due to onset of a-Si:H solid-phase crystallization.

Enhanced Raman scattering in slow-light photonic crystals for chip-scale frequency conversion and optical amplification

We present measurements of enhanced Raman scattering in silicon slow-light photonic crystal waveguides. By utilizing both the Bragg gap edge dispersion of TM-like modes for pump enhancement and the TE-like fundamental mode onset for Stokes enhancement, a six-fold increase in the spontaneous Raman scattering was observed in the double slow-light regime. Both forward and backward Stokes signals are examined, with continuous-wave measurements, in our low-loss photonic crystal membranes. The measured nonlinear enhancement matches well with our numerical model and simulations, and are described in detail in this paper. These observations support the development of chip-scale frequency conversion and optical amplification in silicon nanophotonics.

Ultra-high order ring resonator system with sharp transmission peaks

We propose a relay ring resonator structure which comprises multiple cascaded microring resonators, in which the drop waveguide of a microring resonator is also the input waveguide of the subsequent microring resonator, and so forth. Thus, the transmission response of the relay ring resonator structure has sharp peaks, high out-of-band rejection ratios, and long group delays. A relay ring resonator structure comprising 90 microrings is fabricated on silicon nitride wire waveguides. The simulation and experimental results are in good agreement.

Propagation losses in undoped and n-doped polycrystalline silicon wire waveguides

Polycrystalline silicon (polySi) wire waveguides with width ranging from 200 to 500 nm are fabricated by solid-phase crystallization (SPC) of deposited amorphous silicon (a-Si) on SiO(2) at a maximum temperature of 1000 degrees C. The propagation loss at 1550 nm decreases from 13.0 to 9.8 dB/cm with the waveguide width shrinking from 500 to 300 nm while the 200-nm-wide waveguides exhibit quite large loss (>70 dB/cm) mainly due to the relatively rough sidewall of waveguides induced by the polySi dry etch. By modifying the process sequence, i.e., first patterning the a-Si layer into waveguides by dry etch and then SPC, the sidewall roughness is significantly improved but the polySi crystallinity is degraded, leading to 13.9 dB/cm loss in the 200-nm-wide waveguides while larger losses in the wider waveguides. Phosphorus implantation causes an additional loss in the polySi waveguides. The doping-induced optical loss increases relatively slowly with the phosphorus concentration increasing up to 1 x 10(18) cm(-3), whereas the 5 x 10(18) cm(-3) doped waveguides exhibit large loss due to the dominant free carrier absorption. For all undoped polySi waveguides, further 1-2 dB/cm loss reduction is obtained by a standard forming gas (10%H(2) + 90%N(2)) annealing owing to the hydrogen passivation of Si dangling bonds present in polySi waveguides, achieving the lowest loss of 7.9 dB/cm in the 300-nm-wide polySi waveguides. However, for the phosphorus doped polySi waveguides, the propagation loss is slightly increased by the forming gas annealing.

Observation of zeroth-order band gaps in negative-refraction photonic crystal superlattices at near-infrared frequencies

We present the first observations of zero-n[over ] band gaps in photonic crystal superlattices consisting of alternating stacks of negative-index photonic crystals and positive-index dielectric materials in the near-infrared range. Guided by ab initio three-dimensional numerical simulations, the fabricated nanostructured superlattices demonstrate the presence of zeroth-order gaps in remarkable agreement with theoretical predictions across a range of different superlattice periods and unit cell variations. These volume-averaged zero-index superlattice structures present a new type of photonic band gap, with the potential for complete wave front control for arbitrary phase delay lines and open cavity resonances.

COX-2 inhibition in combination with preoperative chemoradiation for CA esophagus

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Background: Squamous cell carcinoma of the thoracic esophagus (ESCC) is often diagnosed in advanced stage. Pre-operative chemoradiation is employed to downstage the disease before operation. Pathological complete response (pCR) was observed in around 20–40% of patients and was associated with improved survival. Cyclooxygenase 2 (COX-2) is overexpressed in ESCC and may contribute to chemo- and radio-resistance. This pilot study evaluates if COX-2 inhibition in combination with pre-operative chemoradiation will improve the response rate in ESCC. Methods: Patients with histologically confirmed ESCC undergo endoscopic ultrasound, ultrasound of neck and PET/ thoracic, abdominal CT for staging. Patients with disease which is considered potentially resectable are eligible. The primary and involved lymph nodes are irradiated to 40Gy in 20 fractions over 4 weeks with 2 cycles of concurrent cisplatin (100mg/sqm, D1, D22) and 5 fluorouracil (500mg/sqm, D1–5, D22–26). Celecoxib, a specific COX-2 inhibitor, 400mg bid, is started for 2 weeks before chemoradiation, continued throughout chemoradiation and for 4 more weeks after completion of chemoradiation. Patients are re-evaluated and esophagectomy is performed 6–8 weeks after completion of chemoradiation. Results: From 2004 to 2008, 32 patients were recruited. Pre-operative staging was stage II in 4, stage III in 25 and stage IVA in 3 patients. Celecoxib was well tolerated. 3 patients did not have full course of celecoxib: 1 complained of epigastric pain, 1 died early of disease, 1 had renal impairment after chemotherapy. 29 patients had esophagectomy performed after chemoradiation. Median follow-up after completion of chemoradiation was 11 months (range: 3 to 43 months). 23 patients (79.3%) had downstaging of the primary compared with pre-operative staging. The pCR rate in primary tumor was 51.7% (15/29 patients) and pCR rate in lymph nodes was 65.4% (17/26 patients). 3 years overall survival of patients who had esophagectomy was 79.3%. Conclusions: COX-2 inhibition in combination with pre-operative chemoradiation is well tolerated. Preliminary results of the pCR rates and survival are encouraging. Incorporation of COX-2 inhibition into multi-modality treatment of ESCC should be further investigated in a randomized trial.

No significant financial relationships to disclose.

Cascade wide-angle Y-junction 1 x 16 optical power splitter based on silicon wire waveguides on silicon-on-insulator

A 1 x 16 optical power splitter with wide splitting angle, uniform outputs, and low excess loss is demonstrated. The 1 x 16 splitter comprising cascaded 1 x 2 splitters with arc-shaped branching waveguides is fabricated on the silicon-on-insulator (SOI) substrate. The gap between the branching waveguides is widened in a short propagation length such that influences of etch residues and air voids in the gap on the optical power uniformity are reduced significantly. The measured power uniformity of the 1 x 16 splitter is better than 0.3 dB at wavelength of 1550 nm.

Effective thermo-optical enhanced cross-ring resonator MZI interleavers on SOI

A cross-ring (CR-) Mach-Zehnder interferometer (MZI) interleaver structure has been proposed and fabricated. It uses an '8' shaped cross-ring resonator to replace the conventional circular ring resonator. Thus, the new structure can have the function of add-signal. Furthermore, a thermo-optical fine tuning has been applied, which improves the crosstalk performance from approximately -10 dB to approximately -20 dB with 9 V applied on the heater of the 3-dB directional coupler.

Improving coupling efficiency of fiber-waveguide coupling with a double-tip coupler

A double-tip coupler that comprises two inversely and laterally tapered waveguides is experimentally demonstrated for efficient light coupling between a fiber and a sub-micron silicon nitride waveguide. The coupling efficiency of the fabricated double-tip coupler can be improved by as much as over 2 dB per coupling facet, compared with that of a single-tip one with the same tip width of 180 nm. The effect of the gap width of the double tips on the coupling efficiency is studied both in experiment and simulation.

Low propagation loss SiN optical waveguide prepared by optimal low-hydrogen module

We investigated low-hydrogen SiN films prepared by a low temperature (350 degrees C) PECVD method. The impact of SiH(4)/N(2) flow ratio and radio frequency power on the hydrogen content in the SiN films was studied. In this work, we demonstrated a low-loss sub-micron SiN waveguide by using the corresponding optimal SiN films. The propagation loss was found to be as low as -2.1+/-0.2 dB/cm at 1550 nm with waveguide cross-section of 700 nm x 400 nm. The results suggest that the SiN films grown by PECVD with low hydrogen can be used in photonics integrated circuits for new generation communications applications.

Fast and low power Michelson interferometer thermo-optical switch on SOI

We designed and fabricated silicon-on-insulator based Michelson interferometer (MI) thermo-optical switches with deep etched trenches for heat-isolation. Switch power was reduced approximately 20% for the switch with deep etched trenches, and the MI saved approximately 50% power than that of the Mach-Zehnder interferometer. 10.6 mW switch power, approximately 42 micros switch time for the MI with deep trenches, 13.14 mW switch power and approximately 34 micros switch time for the MI without deep trenches were achieved.

Passive ring-assisted Mach-Zehnder interleaver on silicon-on-insulator

A passive ring-assisted Mach-Zehnder interferometer optical interleaver comprising a Y-bench, a 3-dB directional coupler, a ring-resonator, and a delay line is proposed. The interleaver is fabricated with 300 nm x 300 nm silicon wires on silicon-on-insulator. The fabricated interleaver demonstrates a flat-top spectral response. The measured free-spectral range is approximately 4 nm, the insertion loss is approximately -8 dB, and the crosstalk is <- 10 dB. Both the experimental and simulation results are in good agreement.

Electrical transport of bottom-up grown single-crystal Si(1-x)Ge(x) nanowire

In this work, we fabricated an Si(1-x)Ge(x) nanowire (NW) metal-oxide-semiconductor field-effect transistor (MOSFET) by using bottom-up grown single-crystal Si(1-x)Ge(x) NWs integrated with HfO(2) gate dielectric, TaN/Ta gate electrode and Pd Schottky source/drain electrodes, and investigated the electrical transport properties of Si(1-x)Ge(x) NWs. It is found that both undoped and phosphorus-doped Si(1-x)Ge(x) NW MOSFETs exhibit p-MOS operation while enhanced performance of higher I(on)∼100 nA and I(on)/I(off)∼10(5) are achieved from phosphorus-doped Si(1-x)Ge(x) NWs, which can be attributed to the reduction of the effective Schottky barrier height (SBH). Further improvement in gate control with a subthreshold slope of 142 mV dec(-1) was obtained by reducing HfO(2) gate dielectric thickness. A comprehensive study on SBH between the Si(1-x)Ge(x) NW channel and Pd source/drain shows that a doped Si(1-x)Ge(x) NW has a lower effective SBH due to a thinner depletion width at the junction and the gate oxide thickness has negligible effect on effective SBH.

Proposed silicon wire interleaver structure

A Ring-resonator Mach-Zehnder interferometer (RR-MZI) optical interleaver structure comprising a ring resonator (RR) and a 3 dB directional coupler is proposed. The interleaver is fabricated with 300 nm x 300 nm silicon wires on silicon-on-insulator (SOI) wafers. The fabricated interleaver demonstrates a flat-top spectral response, and the measured free spectral range (FSR) is approximately 20 nm. The insertion loss (IL) of the device is approximately -10 dB and the polarization dependent loss (PDL) <5 dB. Both the experimental and simulation results are in good agreement.

Low loss (approximately 6.45dB/cm) sub-micron polycrystalline silicon waveguide integrated with efficient SiON waveguide coupler

In this communication, the sub-micron size polycrystalline silicon (poly- Si) single mode waveguides are fabricated and integrated with SiON waveguide coupler by deep UV lithography. The propagation loss of poly-Si waveguide and coupling loss with optical flat polarization-maintaining fiber (PMF) are measured. For whole C-band (i.e., lambda approximately 1520-1565nm), the propagation loss of TE mode is measured to approximately 6.45+/-0.3dB/cm. The coupling loss with optical flat PMF is approximately 3.4dB/facet for TE mode. To the best of our knowledge, the propagation loss is among the best reported results. This communication discusses the factors reducing the propagation loss, especially the effect of the refractive index contrast. Compared to the SiO(2) cladding, poly-Si waveguide with SiON cladding exhibits lower propagation loss.

Value of intensity modulated radiotherapy for local control and salivary flow compared with conventional radiotherapy for stage II nasopharyngeal carcinoma

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Background: Xerostomia is ubiquitous after conventional radiotherapy (CRT) for nasopharyngeal carcinoma (NPC). Intensity modulated radiotherapy (IMRT) has been advocated to spare the parotids for early disease. However, in T2 disease where there is a need to cover parapharyngeal involvement, it is uncertain if IMRT can still preserve salivary function without compromising local control. Methods: Patients with T2N0/1M0 NPC to be treated with RT alone were eligible. Patients were randomized to receive CRT or IMRT. The end points were salivary flow and local control. The aim was to recruit 25 patients for salivary flow study in each arm. All patients underwent stimulated parotid (SPS) and whole salivary (SWS) flow assessment before RT and at 2, 6 and 12 months after RT. Results: From 2000 to 2005, 42 and 40 patients were randomized to IMRT and CRT respectively. 19 (47.5%) and 27 (64.3%) of patients treated with CRT and IMRT had N1 disease respectively (p=0.18). The median dose for CRT patients was 68 Gy and 75% patients received additional parapharyngeal boost dose of 10 Gy. The median dose to NP for patient treated with IMRT was 70 Gy with no additional boost. Disease control and survival rates were shown in the Table. 25 patients in each arm underwent prospective salivary flow assessment. There was gradual recovery of SWS and SPS among patients treated with IMRT while patient on CRT showed no improvement over time. The mean SWS and SPS flow at 12 months were 26% and 114% of baseline among patients treated with IMRT, compared with 5% and 0% among patients treated with CRT. There was significant difference in SWS and SPS between patients treated with IMRT and CRT at 2, 6 and 12 months post-RT. The average mean dose to parotid gland was 41Gy. Conclusions: IMRT can reserve salivary flow despite a relatively high mean dose to the parotid glands. The significant improvement in local control with IMRT was unexpected but can be due to better coverage of disease with 3-dimensional planning.

No significant financial relationships to disclose.

Enhanced field emission from injector-like ZnO nanostructures with minimized screening effect

Injector-like zinc oxide (ZnO) nanostructures have been synthesized on Si substrate by the vapour phase transport method. Samples with different areal densities were obtained by controlling the temperature. The field emission properties of the injector-like ZnO nanostructures showed a clear dependence on the areal density of the nanostructures, which is due to the screening effect. The samples with a needle length of 850 nm and an areal density of 1 × 10(8) cm(-2) showed the lowest field emission turn-on field of 1.85 V µm(-1) at a current density of 10 µA cm(-2), and the current density reaches 1 mA cm(-2) at an applied field of 4.7 V µm(-1).

Adoptive transfer of autologous Epstein-Barr virus-specific cytotoxic T cells for nasopharyngeal carcinoma

Tumor cells from NPC patients are regularly and latently infected with EBV. To examine whether the virus serves as target for immune intervention of the cancer, we determined levels of EBV-specific CTLp in peripheral blood from NPC patients, long-term survivors of the cancer and healthy subjects. CTLp levels of test subjects varied between 3- 3,000/10(6) PBMCs. The plasma EBV burden increased when the CTLp level fell below 150, whereas the EBV burden of PBMCs was not correlated with CTLp level. Compared with healthy carriers, CTLp levels of patients were lower and varied over a wider range, between 3-1,500/10(6) PBMCs. The quantitative immune deficit was probably attributed to the tumor because, first, CTLp in survivors was restored to levels similar to those in healthy carriers after the tumor had been successfully treated. Second, the CTLp level changed as disease progressed, being lower in local disease, increased in locoregional disease and decreased again when the tumor metastasized. Based on these findings, 4 patients with advanced disease were infused with 5 x 10(7)-3 x 10(8) autologous EBV CTLs. The treatment was safe and unaccompanied by inflammatory or other complications, but whether it improved tumor control could not be discerned from the large tumor bulk. Nevertheless, the treatment regularly increased CTLp levels of patients, maintained it at higher levels for protracted periods and, in 3 patients, restored host surveillance of EBV replication, reducing the plasma EBV burden. Taken together, these results provided a rationale to further explore EBV as a target of immune intervention of NPC.

Pulmonary sequelae of treatment for breast cancer: a prospective study

PURPOSE

To prospectively study the effects of loco-regional radiotherapy in women with breast cancer.

METHODS AND MATERIALS

Thirty consecutive patients with breast resection underwent clinical, lung function, radiographic, and thoracic high-resolution computed tomography evaluation before and at 1, 3, 6, and 12 months after adjuvant radiotherapy. Chemotherapy was also administered to 15 patients.

RESULTS

Nineteen patients reported mild respiratory symptoms at 1 month, which resolved completely at 6 months after radiotherapy. Opacities were present on 80% of chest radiographs and in all patients on high-resolution computed tomography by 3 months. These opacities became compact and persisted on high-resolution computed tomography at 12 months. Lung function indices, including FEV1, FVC, TLC, and DLCO, progressively declined after radiotherapy, and was irreversible at 12 months (p < 0.05). Patients who received chemotherapy did not have significantly different lung function indices compared with their counterparts at all time points (p > 0.05).

CONCLUSIONS

Our results have shown that adjuvant loco-regional radiotherapy, a common practice in breast cancer treatment, is associated with irreversible reduction in lung function parameters. These changes are accompanied by radiological evidence of persistent lung injury. Further studies should be performed to evaluate the incidence and long-term pulmonary sequelae of current treatment for breast cancer.

Patterns of failure after induction chemotherapy and radiotherapy for locoregionally advanced nasopharyngeal carcinoma: the Queen Mary Hospital experience

PURPOSE

Our center contributed 183 patients to the Asian-Oceanian Clinical Oncology Association (AOCOA) multicenter randomized trial comparing induction chemotherapy (CT) followed by radiotherapy (RT) vs. RT alone in patients with locoregionally advanced undifferentiated nasopharyngeal carcinoma (NPC). In a preliminary report no difference in terms of overall survival or relapse-free survival was found between the 2 treatment arms. To study the long-term outcome and patterns of failure after CT for NPC, we analyzed our own center data for which a uniform radiation treatment protocol was adopted and a longer follow-up time was available.

METHODS AND MATERIALS

Between September 1989 and August 1993, a total of 183 patients were recruited into the AOCOA randomized study from our center. Patients with newly diagnosed NPC of Ho's T3 disease, N2-N3 disease, or with neck node size of at least 3 cm were eligible. Stratification was made according to the nodal size (< or = 3 cm, >3- 6 cm, > 6 cm). Patients were randomized to receive 2-3 cycles of CT with cisplatin 60 mg/m(2) and epirubicin 110 mg/m(2) D1 followed by RT or RT alone. Four patients were excluded from the current analysis (2 died before treatment, 2 received treatment elsewhere). The remaining 179 patients were randomized to the two treatment arms, with 92 to the CT arm and 87 to the RT arm. Two patients in the CT arm had RT only, and all patients completed radiation treatment. Overall survival (OAS), relapse-free survival (RFS), local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), and distant metastases-free survival (DMFS) were analyzed using Kaplan--Meier method and significance of survival curve differences calculated using log--rank test. Analysis was performed based on the intent-to-treat.

RESULTS

The median follow-up was 70 months. At the time of analysis, 50% of patients in the CT arm and 61% in the RT arm had relapse, while 32% in the CT arm and 36% in the RT arm had died of the disease. The median RFS was 83 months in the CT arm and 37 months in the RT arm. The median OAS has not yet been reached for both arms. No significant differences were found for the various endpoints, although there was a trend suggesting better nodal control in the CT arm. The 5-year rates for the various endpoints in the CT arm vs. the RT arm were: 53% vs. 42% for RFS (p = 0.13), 70% vs. 67% for OAS (p = 0.68), 80% vs. 77% for LRFS (p = 0.73), 89% vs. 80% for NRFS (p = 0.079), and 70% vs. 68% for DMFS (p = 0.59). There was also no significant difference in the patterns of failure between both arms: in the CT arm, 28% of failures were local only, 13% regional only, 4% locoregional, 44% distant, and 11% mixed locoregional and distant. In the RT arm, 23% of failures were local only, 13% regional only, 11% locoregional, 43% distant, and 9% mixed locoregional and distant.

CONCLUSION

Induction chemotherapy with the regimen used in the current study did not improve the treatment outcome or alter the failure patterns in patients with locoregionally advanced NPC, although there was a trend suggesting better nodal control in the combined modality arm. Alternative strategies of combining chemotherapy and radiotherapy should be tested and employed instead.

Long term results of radioactive gold grain implantation for the treatment of persistent and recurrent nasopharyngeal carcinoma

BACKGROUND

Brachytherapy is useful for the reirradiation of nasopharyngeal carcinoma. In the current study, the long term treatment results of permanent radioactive gold(198) grain interstitial implantation in patients with persistent and recurrent nasopharyngeal carcinoma were reviewed.

METHODS

Gold grain implantation was performed under direct vision with a split palate approach to provide 60 grays (Gy) 0.5 cm away from the plane of implantation. Between August 1986 and May 1999, 106 patients were treated with gold grain implantation (45 patients for persistent disease, 53 patients for first recurrence, and 8 patients for second recurrence in the nasopharynx). All patients had histologically proven disease by biopsy before undergoing implantation.

RESULTS

Patients with persistent disease and those with first recurrence did well with the gold grain implantation. The 5-year local control rates for patients with persistent disease, first recurrence, and second recurrence in the nasopharynx were 87.2%, 62.7%, and 23.4%, respectively (P = 0.0004). The 5-year metastasis free survival rates were 68.1%, 60.3%, and 40%, respectively, for the 3 groups (P = 0.048). The overall survival rates at 5 years for the 3 groups were 79.1%, 53.6%, and 42.9%, respectively (P = 0.0047). Patients with computed tomography evidence of disease extension outside the nasopharynx had a lower local control rate compared with patients whose disease was confined to the nasopharynx (5-year local control rate of 52% vs. 72.3%; P = 0.031). The size of the lesion was not found to be an independent prognostic factor for local control after implantation. Multivariate analysis showed only an indication for implantation (persistent disease, first recurrence, and second recurrence) to be a significant prognostic factor for local control. Complications attributed to gold grain implantation included headache, palatal fistula, and mucosal radiation necrosis at the site of implantation, and were reported to occur in 28.3%, 18.9%, and 16%, respectively, of patients.

CONCLUSIONS

For selected patients with disease confined to the nasopharynx, gold grain implantation is an effective salvage treatment for persistent and recurrent nasopharyngeal carcinoma.

Correlation of endoscopic and histologic findings before and after treatment for nasopharyngeal carcinoma

BACKGROUND

The endoscopic and histologic findings before and after radiotherapy (RT) for nasopharyngeal carcinoma (NPC) were correlated to study the sensitivity and specificity of endoscopic findings in predicting histologic results. The efficiacy of endoscopic examination and post-RT multiple site biopsies in detecting persistent disease was also evaluated.

METHODS

Seven hundred forty-six patients were evaluated. Pre-RT, biopsies were taken from both sides of the nasopharynx to assess the extent of tumor. Four to 16 weeks after RT, routine six-site biopsy specimens were taken from both roofs, lateral, and posterior walls of the nasopharynx and repeated 2 weeks later. Endoscopic findings of exophytic growth, nodule, ulcer, and submucosal bulge were considered "residual tumor," others were considered "no residual tumor." Persistent disease was defined as positive histologic findings 12 weeks after RT.

RESULTS

Before RT, sensitivity of endoscopic findings and biopsy specimens in detecting malignancy were 99.7% and 94.2%, respectively. After RT, sensitivity and specificity of endoscopic findings in predicting positive histologic findings were 29% and 85.8%, respectively, with a positive predictive value of 34.9% and a negative predictive value of 82.2%. Of positive histologic findings, 27.7% were missed in the first session of biopsies; 33.5% of those with positive histologic findings turned out to have persistent disease. For prediction of persistent disease, the sensitivity and specificity of endoscopic findings were 40.4% and 84.4%, with a positive predictive value of 16.3% and a negative predictive value of 95%, and that of histologic findings in the first session of biopsies were 59.6% and 88.3%, respectively, with a positive predictive value of 27.7% and a negative predictive value of 96.7%.

CONCLUSIONS

Endoscopic findings alone have low sensitivity in predicting persistent disease, multiple sites biopsy specimens are indicated. Because only 1.9% of patients with endoscopic findings of "no residual tumor" and negative histologic findings in first session of biopsies had persistent disease, this group can be spared second biopsies. Repeat biopsies are indicated for those with endoscopic findings of "residual tumor" or positive histologic findings in first session of biopsies to improve detection of persistent disease.

Serial HRCT lung changes after 3-field radiation treatment of breast cancer

AIMS

To document serial high resolution computed tomography (HRCT) features of lung injury after 3-field radiotherapy for breast cancer.

MATERIALS AND METHODS

Thirty women who received opposing tangential chest wall and supraclavicular field (SCF) irradiation after breast surgery were recruited. Thoracic HRCT was performed before and at 1, 3, 6 and 12 months after radiotherapy (RT). Lung injury at 3 months was quantified by applying a scoring system to each HRCT section. Findings were correlated with spirometric lung function tests.

RESULTS

There was HRCT evidence of lung injury in 27 (90%) women at 1 month and in all 30 patients at 3 months. Spirometric lung function declined post-RT (P < 0.05), correlating with an increased SCF acute lung injury score at 3 months [r = -0.54 and -0.46, P = 0.01 and 0.03 for forced expiratory volume in 1st (FEV(1)) and forced vital capacity (FVC), respectively]. Lung injury on HRCT progressed from ground glass opacification at 1 month to nodular consolidation (3 months), increasing linear densities (6 months), and finally to residual subpleural linear and dense opacities (12 months).

CONCLUSION

There is a high incidence of lung injury associated with 3-field radiotherapy for breast cancer, with concurrent SCF irradiation increasing the risk of lung damage and functional impairment. A characteristic sequence of HRCT changes is seen in most patients receiving this type of radiotherapy.Ooi, G. C. (2000). Clinical Radiology55, 817-824.

Cytotoxic effect of gossypol on colon carcinoma cells

Gossypol, a male contraceptive drug extracted from cottonseeds, has been found to have antiproliferative activity on tumour cells and is thought to be a potential anticancer drug. The aim of this study was to investigate the mechanisms of gossypol-induced cell death on two colon carcinoma cell lines, HT29 and LoVo. Firstly, we studied the effect of gossypol on the colony forming ability of these tumour cells, which is the main target of chemotherapeutic drugs. Using clonogenic assays, flow cytometry and DNA gel electrophoresis techniques, we have found that gossypol not only inhibited colony forming ability of these tumour cells, but we also observed cellular internucleosomal DNA fragmentation in the cells treated with 3 doses of gossypol and this was accompanied by the appearance of a sub-G1 apoptotic peak and morphological characteristics of apoptosis. Our results suggest that the gossypol induced cell death is via an apoptotic pathway and the effect of gossypol may not be cell cycle specific. Using Western blotting analysis, we found that the gossypol-induced apoptosis may not be involved in the regulation of p53 but possibly associated with the regulation of bcl-2 and Bax expression. Our evidence indicates that gossypol may provide a potential therapeutic benefit for the treatment of colon carcinoma and understanding the mechanisms of gossypol-induced cytotoxicity on tumour cells is essential for including this drug in clinical use.

Recurrent chromosome alterations in hepatocellular carcinoma detected by comparative genomic hybridization

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide and has a very poor prognosis. Fifty primary HCC cases have been analyzed in the present study to explore the association between genomic alteration in primary HCC and clinical features. Several recurrent chromosomal abnormalities were identified in this study. The most frequently detected chromosomal gains involved chromosome arms 1q (33/50 cases, 66%), 8q (24/50 cases, 48%), and 20q (10/50 cases, 20%). High-copy-number amplifications involving 1q (4 cases), 8q (3 cases), and 20q (3 cases) were detected, and a minimum overlapping amplified region at 1q12-q22 was identified. The most frequently detected loss of chromosomal material involved 16q (35/50 cases, 70%), 17p (26/50 cases, 52%), 19p (21/50 cases, 42%), 4q (20/50 cases, 40%), 1p (18/50 cases, 36%), 8p (16/50 cases, 32%), and 22q (14/50 cases, 28%). The associations between genomic alterations detected in the present study and clinical features including clinical stage, tumor size, HBV infection, chronic liver disease, and liver cirrhosis were explored. Our CGH results suggest that the gain of 20q and deletion of 8p are late genetic alterations in HCC, because the incidence of these alterations was obviously increased in the advanced clinical stages. Another finding showed that loss of 8p and gain of 8q and 20q are associated with tumor size. The recurrent gain and loss of chromosomal regions identified in this study provide candidate regions that may contain oncogenes or tumor suppressor genes respectively involved in HCC development and progression.

Effect of p16INK4a on chemosensitivity in nasopharyngeal carcinoma cells

The p16INK4a tumor suppressor gene is frequently inactivated in nasopharyngeal carcinoma (NPC) and hence it may play an important role in the suppression of this tumor. In order to study the effect of p16INK4a restoration in NPC cells, full-length human p16INK4a gene was transfected into a NPC cell line, CNE1. Four individual clones with differential levels of p16INK4a protein expression, were selected for further studies. The introduction of p16INK4a into CNE1 cells induced growth suppression through G0/G1 cell cycle arrest; however, the cell growth rate was not correlated to the levels of p16INK4a protein expression. To study whether transfection of p16INK4a could protect NPC cells from radiation, cisplatin and 5-fluorouracil (5FU), the cellular sensitivity of p16INK4a transfectants and vector control were investigated. An increase in sensitivity to 5FU was observed (2-fold compared to IC50) in all 4 clones compared to vector-transfected control. P16INK4a transfection also resulted in increased sensitivity to cisplatin (1.5-1.8-fold) in 3 out of 4 cell lines. However, no difference in radiosensitivity was found between the p16INK4a transfectants and the control. These findings indicate that p16INK4a suppresses NPC cell growth through G0/G1 arrest and modulating cellular response to chemotherapeutic drugs in NPC cells. Therefore, restoration of p16INK4a may have a therapeutic purpose in the treatment of NPC.

Cyclin D1 expression in oral squamous cell carcinomas: clinicopathological relevance and correlation with p53 expression

The aim of the present study is to study the relationship between cyclin D1 and the clinicopathological features of oral squamous cell carcinomas. The cyclin D1 and p53 expression in oral squamous cell carcinomas from 56 patients (45 men, 11 women) was studied by immunohistochemistry using monoclonal antibodies. The correlation between cyclin D1 and the clinicopathological features of the oral cancers was evaluated. Cyclin D1 expression was found in 63% of oral squamous cell carcinomas; it was often weak but was more frequently positive in high-grade lesions (P=0.019). The expression was positively correlated with p53 expression (P= 0.06). Radiation therapy did not alter the expression of either cyclin D1 or p53 proteins. Expression of these proteins was not related to the age, gender or survival of the patients, or to stages of the tumors. The cyclin D1 expression was more frequently seen in patients with squamous cell carcinomas of oropharynx, palate, floor of mouth and gingiva. To conclude, cyclin D1 was frequently expressed in oral squamous cell carcinomas. This expression was related to the grade of the tumors and was not similar in various regions in the oral cavity, which may indicate the different tumor biology of cancers from these regions.

A phase II study of ifosfamide, 5-fluorouracil and leucovorin in patients with recurrent nasopharyngeal carcinoma previously treated with platinum chemotherapy

The aim of this study was to evaluate the efficacy and toxicity of ifosfamide, 5-fluorouracil (5-FU) and leucovorin (IFL) as a second-line chemotherapy regimen in patients with recurrent undifferentiated nasopharyngeal carcinoma (NPC) previously treated with platinum/5-FU. Between June 1997 and February 1999, 18 patients were entered into the study. 3 patients had loco-regional recurrence, 12 had distant metastases and 3 had both loco-regional recurrence and distant metastases. All patients had previously received platinum/5-FU as adjuvant or palliative treatments. The IFL regimen consisting of ifosfamide 1.2 g/m(2) (with mesna), 5-FU 375 mg/m(2) and leucovorin 20 mg/m(2) for 5 days and was repeated every 21 days. The dose of ifosfamide was escalated to 1.4 and 1.6 g/m(2) in subsequent cycles according to the bone marrow toxicity, and the dose of 5-FU to 450 and 525 mg/m(2) according to the severity of mucositis. Patients received a median of 3 cycles of IFL (range: 2-6), with a median total ifosfamide dose of 21 g/m(2) (range: 13-46) and a median total 5-FU dose of 6.75 g/m(2) (range: 4.1-14.7). The median follow-up was 10 months (range: 4-25). 9 patients (50%) achieved a partial response and 1 patient (6%) achieved a complete response, with an overall response rate of 56% (95% confidence interval (CI): 32-80%). For those patients who responded to IFL, 8 had subsequent disease progression on follow-up, with a median response duration of 7.1 months (95% CI: 5.3-8.9). The median time to progression for all patients was 6.5 months (95% CI: 4.2-8.7). 12 patients are still alive with an estimated 1-year survival probability rate of 51%. Treatments were well tolerated, only 1 patient had grade 3 emesis. None of the patients had grade 3/4 anaemia, leucopenia or thrombocytopenia, although IFL was discontinued in 1 patient because of persisting thrombocytopenia. IFL is an effective second-line regimen in patients with recurrent NPC and is well tolerated with mild toxicity. Combining platinum and IFL in chemonaïve patients may further improve the overall response rate and duration and is worth investigating in future trials.