Mitochondrial diseases in Hong Kong: prevalence, clinical characteristics and genetic landscape

OBJECTIVE

To determine the prevalence of mitochondrial diseases (MD) in Hong Kong (HK) and to evaluate the clinical characteristics and genetic landscape of MD patients in the region.

METHODS

This study retrospectively reviewed the phenotypic and molecular characteristics of MD patients from participating public hospitals in HK between January 1985 to October 2020. Molecularly and/or enzymatically confirmed MD cases of any age were recruited via the Clinical Analysis and Reporting System (CDARS) using relevant keywords and/or International Classification of Disease (ICD) codes under the HK Hospital Authority or through the personal recollection of treating clinicians among the investigators.

RESULTS

A total of 119 MD patients were recruited and analyzed in the study. The point prevalence of MD in HK was 1.02 in 100,000 people (95% confidence interval 0.81-1.28 in 100,000). 110 patients had molecularly proven MD and the other nine were diagnosed by OXPHOS enzymology analysis or mitochondrial DNA depletion analysis with unknown molecular basis. Pathogenic variants in the mitochondrial genome (72 patients) were more prevalent than those in the nuclear genome (38 patients) in our cohort. The most commonly involved organ system at disease onset was the neurological system, in which developmental delay, seizures or epilepsy, and stroke-like episodes were the most frequently reported presentations. The mortality rate in our cohort was 37%.

CONCLUSION

This study is a territory-wide overview of the clinical and genetic characteristics of MD patients in a Chinese population, providing the first available prevalence rate of MD in Hong Kong. The findings of this study aim to facilitate future in-depth evaluation of MD and lay the foundation to establish a local MD registry.

PALI1 promotes tumor growth through competitive recruitment of PRC2 to G9A-target chromatin for dual epigenetic silencing

PALI1 is a newly identified accessory protein of the Polycomb repressive complex 2 (PRC2) that catalyzes H3K27 methylation. However, the roles of PALI1 in cancer are yet to be defined. Here, we report that PALI1 is upregulated in advanced prostate cancer (PCa) and competes with JARID2 for binding to the PRC2 core subunit SUZ12. PALI1 further interacts with the H3K9 methyltransferase G9A, bridging the formation of a unique G9A-PALI1-PRC2 super-complex that occupies a subset of G9A-target genes to mediate dual H3K9/K27 methylation and gene repression. Many of these genes are developmental regulators required for cell differentiation, and their loss in PCa predicts poor prognosis. Accordingly, PALI1 and G9A drive PCa cell proliferation and invasion in vitro and xenograft tumor growth in vivo. Collectively, our study shows that PALI1 harnesses two central epigenetic mechanisms to suppress cellular differentiation and promote tumorigenesis, which can be targeted by dual EZH2 and G9A inhibition.

Posttranslational regulation of FOXA1 by Polycomb and BUB3/USP7 deubiquitin complex in prostate cancer

Forkhead box protein A1 (FOXA1) is essential for androgen-dependent prostate cancer (PCa) growth. However, how FOXA1 levels are regulated remains elusive and its therapeutic targeting proven challenging. Here, we report FOXA1 as a nonhistone substrate of enhancer of zeste homolog 2 (EZH2), which methylates FOXA1 at lysine-295. This methylation is recognized by WD40 repeat protein BUB3, which subsequently recruits ubiquitin-specific protease 7 (USP7) to remove ubiquitination and enhance FOXA1 protein stability. They functionally converge in regulating cell cycle genes and promoting PCa growth. FOXA1 is a major therapeutic target of the inhibitors of EZH2 methyltransferase activities in PCa. FOXA1-driven PCa growth can be effectively mitigated by EZH2 enzymatic inhibitors, either alone or in combination with USP7 inhibitors. Together, our study reports EZH2-catalyzed methylation as a key mechanism to FOXA1 protein stability, which may be leveraged to enhance therapeutic targeting of PCa using enzymatic EZH2 inhibitors.

Polycomb- and Methylation-Independent Roles of EZH2 as a Transcription Activator

Enhancer of Zeste 2 (EZH2) is the enzymatic subunit of Polycomb Repressive Complex 2 (PRC2), which catalyzes histone H3 lysine 27 trimethylation (H3K27me3) at target promoters for gene silencing. Here, we report that EZH2 activates androgen receptor (AR) gene transcription through direct occupancy at its promoter. Importantly, this activating role of EZH2 is independent of PRC2 and its methyltransferase activities. Genome-wide assays revealed extensive EZH2 occupancy at promoters marked by either H3K27ac or H3K27me3, leading to gene activation or repression, respectively. Last, we demonstrate enhanced efficacy of enzymatic EZH2 inhibitors when used in combination with AR antagonists in blocking the dual roles of EZH2 and suppressing prostate cancer progression in vitro and in vivo. Taken together, our study reports EZH2 as a transcriptional activator, a key target of which is AR, and suggests a drug-combinatory approach to treat advanced prostate cancer.

Kim et al. report EZH2 as a transcriptional activator that directly induces AR gene expression in a Polycomb- and methylation-independent manner, providing a mechanism to escape enzymatic EZH2 inhibitors. Combination of inhibitors with AR-targeted therapies showed a strong synergy in blocking the EZH2 downstream pathways and suppressing prostate cancer progression.

Activation of MAPK Signaling by CXCR7 Leads to Enzalutamide Resistance in Prostate Cancer

Castration-resistant prostate cancer (CRPC) that has developed resistance to the new-generation androgen receptor (AR) antagonist enzalutamide is a lethal disease. Transcriptome analysis of multiple prostate cancer models identified CXCR7, an atypical chemokine receptor, as one of the most upregulated genes in enzalutamide-resistant cells. AR directly repressed CXCR7 by binding to an enhancer 110 kb downstream of the gene and expression was restored upon androgen deprivation. We demonstrate that CXCR7 is a critical regulator of prostate cancer sensitivity to enzalutamide and is required for CRPC growth in vitro and in vivo. Elevated CXCR7 activated MAPK/ERK signaling through ligand-independent, but β-arrestin 2-dependent mechanisms. Examination of patient specimens showed that CXCR7 and pERK levels increased significantly from localized prostate cancer to CRPC and further upon enzalutamide resistance. Preclinical studies revealed remarkable efficacies of MAPK/ERK inhibitors in suppressing enzalutamide-resistant prostate cancer. Overall, these results indicate that CXCR7 may serve as a biomarker of resistant disease in patients with prostate cancer and that disruption of CXCR7 signaling may be an effective strategy to overcome resistance. SIGNIFICANCE: These findings identify CXCR7-mediated MAPK activation as a mechanism of resistance to second-generation antiandrogen therapy, highlighting the therapeutic potential of MAPK/ERK inhibitors in CRPC.

TRIM28 protects TRIM24 from SPOP-mediated degradation and promotes prostate cancer progression

TRIM24 is an effector substrate of the E3 ubiquitin ligase adaptor SPOP and becomes stabilized in prostate cancer (PCa) with SPOP mutations. However, how TRIM24 protein is regulated in the vast majority of SPOP-wildtype PCa is unknown. Here we report TRIM28 as a critical upstream regulator of TRIM24. TRIM28 protein interacts with TRIM24 to prevent its ubiquitination and degradation by SPOP. Further, TRIM28 facilitates TRIM24 occupancy on the chromatin and, like TRIM24, augments AR signaling. TRIM28 promotes PCa cell proliferation in vitro and xenograft tumor growth in vivo. Importantly, TRIM28 is upregulated in aggressive PCa and associated with elevated levels of TRIM24 and worse clinical outcome. TRIM24 and AR coactivated gene signature of SPOP-mutant PCa is similarly activated in human PCa with high TRIM28 expression. Taken together, this study provides a novel mechanism to broad TRIM24 protein stabilization and establishes TRIM28 as a promising therapeutic target.

TRIM24 is stabilized in SPOP-mutated prostate cancers, but the regulation of TRIM24 in wild-type prostate cancers is unknown. Here, the authors show that TRIM28 interacts with TRIM24 to prevent SPOP-mediated ubiquitination of TRIM24 and enhances TRIM24 and AR signaling to induce prostate cancer tumorigenesis.

Abstract 4886: Ligand-independent CXCR7 activation of MAPK signaling leads to prostate cancer enzalutamide resistance

Prostate cancer (PC) is the most commonly diagnosed cancer among males in the US. The standard of care for patients with metastatic PC is based on androgen-depletion therapy (ADT), including a first-line chemical castration, and a second-line, treatment with high-affinity antagonists for androgen receptor (AR), e.g. enzalutamide (Enz). Unfortunately, most of the patients eventually relapse with castration-resistant metastatic PC (CRPC). Further, use of Enz is thought to cause a growing concern for prevalence of highly aggressive AR-independent CRPC. Therefore, there is an urgent need for understanding the molecular mechanisms of Enz-resistant (EnzR) CRPC in order to identify novel targeted therapies for deadly PC.

To approach Enz-resistant CRPC we have created EnzR PC cell lines by passaging cells in the presence of sub-lethal doses of Enz for over 6 months. Analyzing the global profiles of expressed genes, we determined CXCR7 (atypical chemokine receptor ACKR3) as one of the top upregulated genes in EnzR cells. Utilizing ChIP-Seq technique we found that AR directly binds to promoter and, at larger scale, enhancer of CXCR7 gene. We identified AR-binding negatively regulates CXCR7 expression; thus, anti-AR therapy unleashes CXCR7 expression in EnzR PC cells. We determined that EnzR PC cells rely on CXCR7-driven signaling in order to survive anti-AR therapy in vitro and in vivo when injected in immunodeficient mice. Moreover, we found that patients with metastatic CRPC increase CXCR7 expression comparing to localized PC tumors. Further, patients who relapsed on second-line ADT demonstrate even higher level of CXCR7 expression.

CXCR7 has a structure of 7-transmembrane (7TM) domains receptor. Activated CXCR7 recruits ARRB2, a cytoplasmic scaffold protein, and internalizes, facilitating activation of MAPK cascade: Raf, MEK, and ERK kinases. CXCR7 can be activated by CXCL12 (SDF1), CXCL11 (ITAC), and MIF. Interestingly, we found that in EnzR PC cells CXCR7 is activated independently from ligand stimulation, causing sustainable ERK phosphorylation (pERK). Thus, we identified that EnzR PC exhibit constitutive accumulation of pro-survival pERK. Accordingly, when we targeted pERK with small molecule inhibitors, we observed decreased EnzR PC survival and growth in vitro and in vivo.

Taken together these data suggest that CXCR7-ERK signaling axis plays a pivotal role in progression to Enz-resistant CRPC, facilitating survival and growth of tumor cells during and after second-line of ADT. Currently, we are focusing on further understanding the molecular mechanisms of CXCR7-ERK tumor-promoting activity. In parallel, we are evaluating the efficacy of CXCR7-ERK targeting for Enz-resistant CRPC and its translatability to the clinics as a novel targeted therapy for patients who relapsed on advanced ADT with deadly CRPC.

Citation Format: Shangze Li, Ka-Wing Fong, Galina Gritsina, Ali Zhang, Jonathan C. Zhao, Jung Kim, Jindan Yu. Ligand-independent CXCR7 activation of MAPK signaling leads to prostate cancer enzalutamide resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4886.

Abstract 1521: Role of Trim28 in prostate cancer

TRIM28 is an essential gene during embryonic development, which is involved in a wide range of biologic processes. From the pathologic viewpoint, TRIM28 overexpression was proved to broadly exist in pancreatic, liver, breast, glioma and lung cancer, and often expression of TRIM28 is correlated with clinical stage. Functional assays have demonstrated that TRIM28 promotes cancer cell growth and metastasis, further supporting TRIM28 as a promising target for therapeutic intervention. For past decade, TRIM28 is considered to be a transcriptional co-repressor due to TRIM28-dependent recruitment of histone modifiers such as CHD1/NuRD complex and SETDB1 for histone methylation and heterochromatin formation to achieve gene silencing. Surprisingly, transcriptome study revealed that TRIM28 can activate the expression of its target genes as much as it represses, hypothesizing the main role of TRIM28 may not lie in transcriptional repression. In addition, recent findings demonstrated that TRIM28 interacts with 7SK snRNP complex, which facilitates P-TEFb kinase module recruitment and productive transcription elongation at inducible genes. This evidence implicated that TRIM28 may form distinct complexes to induce or repress gene expression in context-dependent manner. On top of that, it remains unclear about the role of TRIM28 in prostate cancer. Our preliminary study revealed that TRIM28 is upregulated in castration-resistant prostate cancer (CRPC). TRIM28 knockdown markedly decreased prostate cancer cell proliferation, clonogenicity as well as CRPC-xenograft tumor growth. Moreover, proteomic analysis in LNCaP prostate cancer cells revealed that TRIM28 associates with a number of transcription co-activators. Gene expression profiling showed that androgen signaling is positively regulated by TRIM28. We proposed that TRIM28 forms the transcription activation complexes that modulate gene expression of various oncogenic pathway and promote PCa progression.

Citation Format: Ka-Wing Fong, Jonathan Zhao, Bin Zheng, Jindan Yu. Role of Trim28 in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1521.

Abstract 2080: Polycomb-mediated disruption of an AR-feedback loop drives castration-resistant prostate cancer

Androgen receptor (AR) is an androgen-stimulated transcription factor that critically promotes prostate cancer development and progression. In addition to its conventional role in transcriptional activation, AR also acts as a transcriptional repressor to directly inhibit target gene expression. Through meta-analysis of androgen-regulated expression microarray data, we nominated CCN3/NOV, a CCN family protein, as one of the top AR-repressed genes in prostate cancer, implicating that CCN3 may play a tumor suppressive role in prostate cancer development. Therefore, we sought to investigate the molecular functions of CCN3 and its roles in prostate cancer progression especially in castration-resistant prostate cancer (CRPC). We first showed that CCN3 protein physically interacts with AR. The CCN3 interaction domain was mapped in the N-terminal domain of AR which is also present in constitutively active AR variants. Using immunofluorescence microscopy as well as subcellular fractionation technique, we demonstrated that CCN3 sequesters AR or AR variants into the cytoplasm to inhibit AR nuclear translocation, which in turn suppresses AR chromatin targeting and transcriptional activation. However, this negative feedback loop between AR and AR-repressed gene CCN3is disrupted in CRPC through CCN3 persistent epigenetic silencing by the Polycomb group protein EZH2, rendering AR transcriptional activation and CRPC progression. Taking advantage of this repressive mechanism, we restored CCN3 in CRPC cell model, either through ectopic overexpression or treatment with EZH2 inhibitor, which results in strong suppression of CRPC cell proliferation and anchorage-independent cell growth. Consistently, application of EZH2 inhibitor remarkably reduced tumor size in a castrated mice model. Taken together, our data highlight CCN3 as a novel regulator of AR signaling and support the promise of EZH2-targeting agents in treating CRPC.

Citation Format: Ka-Wing Fong, Jonathan Zhao, Jung Kim, Shangze Li, Angela Yang, Bing Song, Laure Rittié, Ming Hu, Ximing Yang, Bernard Perbal, Jindan Yu. Polycomb-mediated disruption of an AR-feedback loop drives castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2080. doi:10.1158/1538-7445.AM2017-2080

Microtubule plus-end tracking of end-binding protein 1 (EB1) is regulated by CDK5 regulatory subunit-associated protein 2

Microtubules are polar cytoskeleton filaments that extend via growth at their plus ends. Microtubule plus-end-tracking proteins (+TIPs) accumulate at these growing plus ends to control microtubule dynamics and attachment. The +TIP end-binding protein 1 (EB1) and its homologs possess an autonomous plus-end-tracking mechanism and interact with other known +TIPs, which then recruit those +TIPs to the growing plus ends. A major +TIP class contains the SXIP (Ser-X-Ile-Pro, with X denoting any amino acid residue) motif, known to interact with EB1 and its homologs for plus-end tracking, but the role of SXIP in regulating EB1 activities is unclear. We show here that an interaction of EB1 with the SXIP-containing +TIP CDK5 regulatory subunit-associated protein 2 (CDK5RAP2) regulates several EB1 activities, including microtubule plus-end tracking, dynamics at microtubule plus ends, microtubule and α/β-tubulin binding, and microtubule polymerization. The SXIP motif fused with a dimerization domain from CDK5RAP2 significantly enhanced EB1 plus-end-tracking and microtubule-polymerizing and bundling activities, but the SXIP motif alone failed to do so. An SXIP-binding-deficient EB1 mutant displayed significantly lower microtubule plus-end tracking than the wild-type protein in transfected cells. These results suggest that EB1 cooperates with CDK5RAP2 and perhaps other SXIP-containing +TIPs in tracking growing microtubule tips. We also generated plus-end-tracking chimeras of CDK5RAP2 and the adenomatous polyposis coli protein (APC) and found that overexpression of the dimerization domains interfered with microtubule plus-end tracking of their respective SXIP-containing chimeras. Our results suggest that disruption of SXIP dimerization enables detailed investigations of microtubule plus-end-associated functions of individual SXIP-containing +TIPs.

Polycomb-Mediated Disruption of an Androgen Receptor Feedback Loop Drives Castration-Resistant Prostate Cancer

The lethal phenotype of castration-resistant prostate cancer (CRPC) is generally caused by augmented signaling from the androgen receptor (AR). Here, we report that the AR-repressed gene CCN3/NOV inhibits AR signaling and acts in a negative feedback loop to block AR function. Mechanistically, a cytoplasmic form of CCN3 interacted with the AR N-terminal domain to sequester AR in the cytoplasm of prostate cancer cells, thereby reducing AR transcriptional activity and inhibiting cell growth. However, constitutive repression of CCN3 by the Polycomb group protein EZH2 disrupted this negative feedback loop in both CRPC and enzalutamide-resistant prostate cancer cells. Notably, restoring CCN3 was sufficient to effectively reduce CPRC cell proliferation in vitro and to abolish xenograft tumor growth in vivo Taken together, our findings establish CCN3 as a pivotal regulator of AR signaling and prostate cancer progression and suggest a functional intersection between Polycomb and AR signaling in CRPC. Cancer Res; 77(2); 412-22. ©2016 AACR.

FOXA1 potentiates lineage-specific enhancer activation through modulating TET1 expression and function

Forkhead box A1 (FOXA1) is an FKHD family protein that plays pioneering roles in lineage-specific enhancer activation and gene transcription. Through genome-wide location analyses, here we show that FOXA1 expression and occupancy are, in turn, required for the maintenance of these epigenetic signatures, namely DNA hypomethylation and histone 3 lysine 4 methylation. Mechanistically, this involves TET1, a 5-methylcytosine dioxygenase. We found that FOXA1 induces TET1 expression via direct binding to its cis-regulatory elements. Further, FOXA1 physically interacts with the TET1 protein through its CXXC domain. TET1 thus co-occupies FOXA1-dependent enhancers and mediates local DNA demethylation and concomitant histone 3 lysine 4 methylation, further potentiating FOXA1 recruitment. Consequently, FOXA1 binding events are markedly reduced following TET1 depletion. Together, our results suggest that FOXA1 is not only able to recognize but also remodel the epigenetic signatures at lineage-specific enhancers, which is mediated, at least in part, by a feed-forward regulatory loop between FOXA1 and TET1.

Telephone and Teleradiology-Guided Thrombolysis Can Achieve Similar Outcome as Thrombolysis by Neurologist On-site

BACKGROUND

Because of the limitation of on-site neurology workforce, telestroke was implemented to overcome this barrier. We explored the efficacy and safety of intravenous (IV) stroke thrombolysis service by telestroke when neurologist was not available on-site.

METHODS

From January 2009 to December 2012, we compared patients treated with IV stroke thrombolysis by telestroke in the form of telephone consultation with teleradiology, to patients treated after in-person assessment by the same team of neurologists in a regional hospital. Door-to-needle time, symptomatic intracranial hemorrhage, and functional outcome at 3 months were prospectively collected and compared between the groups.

RESULTS

In all, 152 patients were treated with IV thrombolysis; 102 patients were treated with neurologist on-site; whereas 50 patients were treated by internists with telestroke. Fifty-two percent of the telemedical group achieved excellent outcome compared to 43% of the neurologist on-site group (P = .30). Symptomatic intracranial hemorrhage rate (4.0% versus 4.9%, P = 1.0) and mortality (8.3% versus 11.9%, P = .49) were comparable. Using the multiple logistic regression analysis, age, baseline stroke severity, and extent of early ischemic change on brain computed tomography scan, are independent predictors for excellent outcome, whereas the presence of neurologist on-site is not correlated with the outcome.

CONCLUSIONS

Patients treated without neurologist on-site achieved similar outcome. Telephone consultation and teleradiology-guided IV stroke thrombolysis, with the support of on-site internist appeared safe and efficacious.

Fam118B, a newly identified component of Cajal bodies, is required for Cajal body formation, snRNP biogenesis and cell viability

Cajal bodies are specialized and dynamic compartments in the nucleus that are involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs). Because of the dynamic and varied roles of Cajal bodies, it is of great interest to identify the components of Cajal bodies to better understand their functions. We performed a genome-wide screen to identify proteins that colocalize with coilin, the marker protein of Cajal bodies. In this study, we identified and characterized Fam118B as a newly discovered component of Cajal bodies. Fam118B is widely expressed in a variety of cell lines derived from various origins. Overexpression of Fam118B changes the canonical morphology of Cajal bodies, whereas depletion of Fam118B disrupts the localization of components of Cajal bodies, including coilin, the survival of motor neuron protein (SMN) and the Sm protein D1 (SmD1, also known as SNRPD1). Moreover, depletion of Fam118B reduces splicing capacity and inhibits cell proliferation. In addition, Fam118B associates with coilin and SMN proteins. Fam118B depletion reduces symmetric dimethylarginine modification of SmD1, which in turn diminishes the binding of SMN to this Sm protein. Taken together, these data indicate that Fam118B, by regulating SmD1 symmetric dimethylarginine modification, plays an important role in Cajal body formation, snRNP biogenesis and cell viability.

Whole-genome screening identifies proteins localized to distinct nuclear bodies

The nucleus is a unique organelle that contains essential genetic materials in chromosome territories. The interchromatin space is composed of nuclear subcompartments, which are defined by several distinctive nuclear bodies believed to be factories of DNA or RNA processing and sites of transcriptional and/or posttranscriptional regulation. In this paper, we performed a genome-wide microscopy-based screening for proteins that form nuclear foci and characterized their localizations using markers of known nuclear bodies. In total, we identified 325 proteins localized to distinct nuclear bodies, including nucleoli (148), promyelocytic leukemia nuclear bodies (38), nuclear speckles (27), paraspeckles (24), Cajal bodies (17), Sam68 nuclear bodies (5), Polycomb bodies (2), and uncharacterized nuclear bodies (64). Functional validation revealed several proteins potentially involved in the assembly of Cajal bodies and paraspeckles. Together, these data establish the first atlas of human proteins in different nuclear bodies and provide key information for research on nuclear bodies.

Dynamic recruitment of CDK5RAP2 to centrosomes requires its association with dynein

CDK5RAP2 is a centrosomal protein known to be involved in the regulation of the γ-tubulin ring complex and thus the organization of microtubule arrays. However, the mechanism by which CDK5RAP2 is itself recruited to centrosomes is poorly understood. We report here that CDK5RAP2 displays highly dynamic attachment to centrosomes in a microtubule-dependent manner. CDK5RAP2 associates with the retrograde transporter dynein-dynactin and contains a sequence motif that binds to dynein light chain 8. Significantly, disruption of cellular dynein-dynactin function reduces the centrosomal level of CDK5RAP2. These results reveal a key role of the dynein-dynactin complex in the dynamic recruitment of CDK5RAP2 to centrosomes.

RIF1 counteracts BRCA1-mediated end resection during DNA repair

BRCA1 promotes homologous recombination repair and antagonizes 53BP1-dependent nonhomologous end joining (NHEJ) pathway. However, the molecular basis of the competition between BRCA1 and 53BP1 pathways remains elusive. Here we report that RIF1 protein translocates to damage sites via ATM-dependent 53BP1 phosphorylation. Strikingly, loss of RIF1 rescues initial DNA end resection and checkpoint activation in BRCA1-depleted cells. Interestingly RIF1 accumulation at damage sites is antagonized by BRCA1 in S and G2 phases. Conversely, the translocation of BRCA1 to damage sites is inhibited by RIF1 in G1 phase. However, loss of RIF1 differs from that of 53BP1 deficiency, as it cannot fully rescue RAD51 foci formation, homologous recombination defect, and radio-hypersensitivity in BRCA1-deficient cells. This is likely because RIF1, but not 53BP1, also regulates the foci formation and chromatin loading of BLM (the Bloom syndrome helicase). Thus, RIF1 not only acts downstream of 53BP1 and counteracts BRCA1-mediated end resection but also has a secondary role in promoting BLM function in DNA repair.

Proliferating cell nuclear antigen (PCNA)-binding protein C1orf124 is a regulator of translesion synthesis

DNA damage-induced proliferating cell nuclear antigen (PCNA) ubiquitination serves as the key event mediating post-replication repair. Post-replication repair involves either translesion synthesis (TLS) or damage avoidance via template switching. In this study, we have identified and characterized C1orf124 as a regulator of TLS. C1orf124 co-localizes and interacts with unmodified and mono-ubiquitinated PCNA at UV light-induced damage sites, which require the PIP box and UBZ domain of C1orf124. C1orf124 also binds to the AAA-ATPase valosin-containing protein via its SHP domain, and cellular resistance to UV radiation mediated by C1orf124 requires its interactions with valosin-containing protein and PCNA. Interestingly, C1orf124 binds to replicative DNA polymerase POLD3 and PDIP1 under normal conditions but preferentially associates with TLS polymerase η (POLH) upon UV damage. Depletion of C1orf124 compromises PCNA monoubiquitination, RAD18 chromatin association, and RAD18 localization to UV damage sites. Thus, C1orf124 acts at multiple steps in TLS, stabilizes RAD18 and ubiquitinated PCNA at damage sites, and facilitates the switch from replicative to TLS polymerase to bypass DNA lesion.

Retrospective review of diagnostic performance of intracranial translucency in detection of open spina bifida at the 11-13-week scan

OBJECTIVES

To evaluate diagnostic performance of intracranial translucency (IT) for detection of open spina bifida and interobserver agreement for visualization of IT during the 11-13-week scan.

METHODS

A retrospective study was undertaken in a tertiary referral center. Two hundred 11-13-week scans for nuchal translucency, performed by sonographers certified by The Fetal Medicine Foundation, U.K., were reviewed independently for IT by two expert observers. When IT was not seen, the observers determined whether this was due to poor IT image quality or the presence of spina bifida. Discordant cases were reviewed by a third observer and the majority decision was used for analysis. All observers were blinded to individual pregnancy outcome and the number of cases with spina bifida.

RESULTS

There were 191 normal fetuses, eight fetuses with open spina bifida and one with closed spina bifida (this case was excluded from analysis). IT was seen in 150 fetuses and all were normal. In six of the 49 cases in which IT was not seen, IT non-visibility was attributed to open spina bifida; among these cases, four fetuses had open spina bifida and two were normal. In the remaining 43 cases (including 39 normal fetuses), IT non-visibility was attributed to inadequate image quality. Sensitivity was 50% (4/8) and specificity was 99% (150/152). Concordance between the two observers concerning IT visibility was 79%, (κ = 0.47, representing moderate agreement).

CONCLUSION

There was moderate interobserver agreement for visualization of IT on images obtained for nuchal translucency measurement at 11-13 weeks. When IT was confidently seen, open spina bifida could be excluded. However, non-visibility of IT correctly diagnosed only 50% of fetuses with open spina bifida.

Malignant pleural mesothelioma in Singapore

AIM

To examine the clinical characteristics and outcomes of malignant pleural mesothelioma (MPM) in Singapore.

METHODS AND MATERIALS

A retrospective case note review of patients diagnosed with MPM between 1997 and 2007. Overall survival (OS), locoregional recurrence-free survival (LRS) and metastasis-free survival (MFS) were estimated using Kaplan Meier method and comparison were done using log rank test. Multivariate analysis was not done due to the small number of patients.

RESULTS

There were 39 patients diagnosed with MPM. Fifty-nine percent of patients presented with Stage III and IV disease. Eight (21%) patients had surgery with 2 patients receiving trimodality treatment and adjuvant chemotherapy respectively. Three patients received adjuvant RT and one patient had no adjuvant therapy. Twelve patients received palliative RT or chemotherapy. Median follow-up was 27.0 weeks. Median overall survival (OS) for all patients was 8.0 months (95% CI 6.3-9.7). One-year and 2-year OS were 25.6% and 6.4% respectively. Thirty-eight patients died of progressive disease and one patient died of other cause. Locoregional recurrences and distant metastases occurred in 3/8 and 5/8 surgically treated patients respectively. Overall, distant metastases occurred in 44% of patients. Surgery did not affect survival outcomes although patients with dual modality treatment showed a trend towards improved survival. Epithelioid tumours had better prognosis (median OS 10.2 months) compared to biphasic (median OS 8.0 months) and sarcomatoid tumours (median OS 1.4 months).

CONCLUSION

Future management of MPM will need to emphasize on both locoregional and systemic control and hence, inclusion of patients in clinical trials for multimodality treatment should be encouraged.

Interaction of CDK5RAP2 with EB1 to track growing microtubule tips and to regulate microtubule dynamics

Mutations in cdk5rap2 are linked to autosomal recessive primary microcephaly, and attention has been paid to its function at centrosomes. In this report, we demonstrate that CDK5RAP2 localizes to microtubules and concentrates at the distal tips in addition to centrosomal localization. CDK5RAP2 interacts directly with EB1, a prototypic member of microtubule plus-end tracking proteins, and contains the basic and Ser-rich motif responsible for EB1 binding. The EB1-binding motif is conserved in the CDK5RAP2 sequences of chimpanzee, bovine, and dog but not in those of rat and mouse, suggesting a function gained during the evolution of mammals. The mutation of the Ile/Leu-Pro dipeptide within the motif abolishes EB1 interaction and plus-end attachment. In agreement with the mutational analysis, suppression of EB1 expression inhibits microtubule tip-tracking of CDK5RAP2. We have also found that the CDK5RAP2-EB1 complex regulates microtubule dynamics and stability. CDK5RAP2 depletion by RNA interference impacts the dynamic behaviors of microtubules. The CDK5RAP2-EB1 complex induces microtubule bundling and acetylation when expressed in cell cultures and stimulates microtubule assembly and bundle formation in vitro. Collectively, these results show that CDK5RAP2 targets growing microtubule tips in association with EB1 to regulate microtubule dynamics.

CDK5RAP2 is a pericentriolar protein that functions in centrosomal attachment of the gamma-tubulin ring complex

Microtubule nucleation and organization by the centrosome require gamma-tubulin, a protein that exists in a macromolecular complex called the gamma-tubulin ring complex (gammaTuRC). We report characterization of CDK5RAP2, a novel centrosomal protein whose mutations have been linked to autosomal recessive primary microcephaly. In somatic cells, CDK5RAP2 localizes throughout the pericentriolar material in all stages of the cell cycle. When overexpressed, CDK5RAP2 assembled a subset of centrosomal proteins including gamma-tubulin onto the centrosomes or under the microtubule-disrupting conditions into microtubule-nucleating clusters in the cytoplasm. CDK5RAP2 associates with the gammaTuRC via a short conserved sequence present in several related proteins found in a range of organisms from fungi to mammals. The binding of CDK5RAP2 is required for gammaTuRC attachment to the centrosome but not for gammaTuRC assembly. Perturbing CDK5RAP2 function delocalized gamma-tubulin from the centrosomes and inhibited centrosomal microtubule nucleation, thus leading to disorganization of interphase microtubule arrays and formation of anastral mitotic spindles. Together, CDK5RAP2 is a pericentriolar structural component that functions in gammaTuRC attachment and therefore in the microtubule organizing function of the centrosome. Our findings suggest that centrosome malfunction due to the CDK5RAP2 mutations may underlie autosomal recessive primary microcephaly.

Cochlear implantation in postirradiated ears: outcomes and challenges

OBJECTIVES

Radiotherapy to head and neck tumors can potentially damage the auditory pathways. This has relevance in cochlear implants and there is a need for clinical studies to confirm the feasibility of cochlear implantation in these patients.

METHODS

The records of all patients who had received cochlear implants at our institution were reviewed in this retrospective study and those who had prior irradiation for head and neck tumors were further studied. Case controls consisted of comparable cochlear implant recipients who did not have prior radiotherapy.

RESULTS

Four of 230 patients met the criteria for further study. They had received radiotherapy for nasopharyngeal carcinoma 11 to 28 years ago and the postimplant follow-up period ranged from 9 to 46 months. The implanted ear of each patient had favorable preoperative promontory stimulation results. Postimplant, all patients were satisfied with their hearing outcomes and the improvement in speech discrimination scores was comparable to the controls. These cases also illustrated specific clinical concerns, including 1) radiation-induced endocrine dysfunction was common and, if overlooked, could result in increased anesthetic risks, and 2) irreversible eustachian tube dysfunction led to chronic middle ear problems, which complicated surgery; the use of modified surgical techniques overcame these difficulties.

CONCLUSIONS

Deafened postirradiated patients with nasopharyngeal carcinoma were able to achieve good postimplant hearing outcomes comparable to those of nonirradiated patients. Should cochlear implantation be indicated in patients who have had prior radiation to the head and neck, specific preoperative, intraoperative, and postoperative issues have to be addressed.

Effect of radiotherapy on retro-cochlear auditory pathways

OBJECTIVES

The cochlea may be damaged by modern conventional radiotherapy (RT) for head and neck cancers when the ear is included in the radiation field. It is unclear however, if the retro-cochlear auditory pathways are affected as well, which has clinical significance in cochlear implantation. This study aims to investigate the integrity of the retro-cochlear auditory pathways in patients who had received RT for nasopharyngeal carcinoma.

STUDY DESIGN

Prospective study.

METHODS

Patients who were newly diagnosed with nasopharyngeal carcinoma and treated by RT alone were studied. Evoked response audiometry and PTAs were carried out prior to and after RT (at 3, 18, and 48 months postRT). In addition, evoked response audiometry was also performed during the 3rd, 5th, and 7th week of RT. Waves 1 to 5, 1 to 3, and 3 to 5 latencies were measured. The values recorded during and postRT were compared with those recorded before RT. In addition, a subset of ears that demonstrated postRT sensorineural hearing loss were identified so that their respective wave 1 to 5 interwave latencies could be similarly compared. Wilcoxon signed ranks test was used in the statistical analysis. To confirm that the cochlea and internal auditory meatus receive significant doses of radiation, the RT treatment plans of nine other nasopharyngeal carcinoma patients treated by the same RT technique were analyzed to derive dose-volume histograms of these structures.

RESULTS

Twenty-seven patients (20 males and 7 females) with a mean age of 51.2 (range 36-75) years participated in the study. There was no statistically significant difference in waves 1 to 5, 1 to 3, and 3 to 5 interwave latencies recorded during RT and postRT as compared with those recorded before RT (P > .05). Pre- and postRT wave 1 to 5 latencies of the 16 ears that had postRT hearing deterioration were also not statistically significant (P = .366). The mean radiation doses delivered to the cochlea and internal auditory meatus ranged from 24.1 to 62.2 Gy and 14.4 to 43.4 Gy, respectively.

CONCLUSION

This study suggests in patients who have had RT for nasopharyngeal carcinoma, the retro-cochlear auditory pathways are functionally intact even in the longer term.

Prenatal ultrasound findings of lissencephaly associated with Miller-Dieker syndrome and comparison with pre- and postnatal magnetic resonance imaging

OBJECTIVE

To report on the prenatal ultrasound findings in fetuses with lissencephaly associated with Miller-Dieker syndrome (MDS) and to compare these findings with those of magnetic resonance imaging (MRI).

METHODS

Cases of MDS confirmed by postnatal chromosome microdeletion analysis were identified through review of patient records. Prenatal ultrasound scans were reviewed retrospectively by two radiologists. For cerebral cortical development, the Sylvian, parieto-occipital and calcarine fissures, and the cingulate sulcus and sulci over the cerebral convexity were evaluated. If one or more of these fissures or sulci were not visualized at the expected gestational age or their appearance was abnormal for gestational age, cortical development was considered delayed. Prenatal and postnatal MRI examinations were reviewed by a pediatric neuroradiologist.

RESULTS

There were seven cases of MDS. In three cases, the prenatal diagnosis of agyria/lissencephaly was prospectively suspected by ultrasound at 23, 26 and 30 weeks, and subsequently confirmed by prenatal MRI. When we retrospectively reviewed the prenatal ultrasound scans of all fetuses, all had delayed cortical development identified on ultrasound performed after 23 weeks' gestation. In all cases the Sylvian fissure was abnormal on both ultrasound and MRI. In one fetus, a normal cortical appearance for gestational age was seen at the initial 20-week ultrasound examination, but delayed cortical development was identified at a 24-week scan. Mild ventriculomegaly was seen in six fetuses and dysgenesis of the corpus callosum in one. Extracranial abnormalities were detected in five fetuses. Delayed cortical development was seen in two fetuses with mild ventriculomegaly, but no other fetal anomalies.

CONCLUSIONS

In fetuses with MDS, delayed cortical development can be suspected on ultrasound as early as 23 weeks' gestation. This finding warrants further investigations including MRI and FISH analysis for chromosome 17p13.3 deletion.

How early are fetal cerebral sulci visible at prenatal ultrasound and what is the normal pattern of early fetal sulcal development?

OBJECTIVES

To evaluate the time of appearance and pattern of development of fetal cerebral sulci at prenatal ultrasound.

METHODS

We studied 50 normal fetuses for visibility of cerebral sulci, especially sulci which appear early in anatomical studies, namely the parieto-occipital fissure, calcarine sulcus, cingulate sulcus, convexity sulci and insula/Sylvian fissure. The gestational ages of the fetuses studied ranged from 15.6 to 29.6 weeks.

RESULTS

Sulci could be seen by transabdominal ultrasound as early as 18.5 weeks. Medial hemispheric sulci and the insula were visible earlier and more confidently than convexity sulci. The earliest gestational ages at which specific sulci could be seen in any fetus were as follows: parieto-occipital fissure 18.5 weeks, calcarine sulcus 18.5 weeks, cingulate sulcus 23.2 weeks and convexity sulci 23.2 weeks. In the present series, the gestational ages at which these sulci were always visible were as follows: parieto-occipital fissure >20.5 weeks, calcarine sulcus >21.9 weeks, cingulate sulcus >24.3 weeks and convexity sulci >27.9 weeks. The insula and its margin (the circular sulcus) and the overgrowing opercula undergo characteristic maturation. The circular sulcus at the margin of the insula was initially smooth but started becoming angular after about 17 weeks as it started to be overgrown by the parietal and temporal lobe opercula. Initially the insula/operculum angle was obtuse. An acute angle was first evident at 23.2 weeks and in all fetuses older than 24.5 weeks. Our ultrasound data were consistent with anatomical studies and fetal magnetic resonance imaging findings.

CONCLUSIONS

Some cerebral sulci can be seen at prenatal ultrasound as early as 18.5 weeks. Familiarity with the normal pattern of sulcal development and the discriminating gestational ages for the appearance of different sulci may allow early suspicion of lissencephaly.

Design of a prognostic index score for metastatic nasopharyngeal carcinoma

The survival outcome of patients with systemic cancer differs significantly between individuals even within the same tumour type. We set out to illustrate this by analysing the factors determining survival in patients with metastatic disease from nasopharyngeal carcinoma (NPC) and to design a scoring system based on these prognostic factors. Patients referred between January 1994 and December 1999 were retrospectively analysed. Factors analysed included patient (age group, gender, performance status (BS) at diagnosis of metastases), disease (number of metastatic sites, specific metastatic sites, disease-free interval (DFI), metastases at presentation, presence of locoregional recurrence), and laboratory factors (leucocyte count, haemoglobin level, albumin level). Univariate and multivariable analyses were performed using the Cox proportion hazards model. A numerical score was derived from the regression coefficients of each independent prognostic variable. The prognostic index score (PIS) of each patient was calculated by totalling up the scores of each independent variable. Independently significant, negative prognostic factors were liver metastasis, lung metastasis, anaemia, poor PS, distant metastasis at initial diagnosis, and a DFI of <6 months. Three prognostic groups based on the PIS were obtained: (i) good risk (PIS=0-6); (ii) intermediate risk (7-10); (iii) poor risk (>or=11). The median survivals for these groups were 19.5, 10, and 5.8, months, respectively, (log rank test: P<0.0001). The variable prognosis of patients with disseminated NPC can be assessed by using easily available clinical information (patient, disease and laboratory factors). The PIS system will need to be validated on prospectively collected data of another cohort of patients.

Gemcitabine in metastatic nasopharyngeal carcinoma of the undifferentiated type

BACKGROUND

We conducted two parallel phase II trials in chemonaïve and previously treated patients with metastatic nasopharyngeal carcinoma (NPC) to evaluate the tumour response, progression-free and overall survival, and toxicity of gemcitabine.

PATIENTS AND METHODS

Gemcitabine 1250 mg/m2 was given on days 1 and 8 of a 21-day cycle. Patients with an Eastern Cooperative Oncology Group performance status <2, adequate renal, hepatic and bone marrow function, and radiologically measurable NPC were eligible.

RESULTS

Twenty-five chemonaïve and 27 previously treated patients were enrolled. The overall response rate was 28% [95% confidence interval (CI) 14% to 48%] for the chemonaïve and 48% (95% CI 31% to 66%) for previously treated patients. Toxicities greater than or equal to grade 3 occurred in 15 (60%) chemonaïve and 13 (48%) previously treated patients. Neutropenia was uncommon in chemonaïve patients, but occurred in 37% of previously treated patients. The median time to progression was 3.6 months (range 0.9-7.9) for chemonaïve and 5.1 months (0.9-13.1) for previously treated patients. Median overall survival time was 7.2 months (1.4-15.6) and 10.5 months (2.4-15.0) for chemonaïve and previously treated patients, respectively.

CONCLUSIONS

Gemcitabine has moderate activity in NPC with minimal toxicity, and is also an effective salvage agent for patients who have failed or progressed after treatment with other agents.

Cerebellopontine angle involvement by nasopharyngeal carcinoma

OBJECTIVE

This article describes a series of patients with nasopharyngeal carcinoma involvement of the cerebellopontine angle and discusses the clinical significance of this entity.

SETTING

Tertiary referral center.

STUDY DESIGN

Retrospective case study.

PATIENTS

Patients who were diagnosed with nasopharyngeal carcinoma with clinical features of cerebellopontine involvement by tumor.

INTERVENTIONS

Cerebellopontine involvement by tumor confirmed by computed tomography, magnetic resonance imaging, or both.

RESULTS

Patients with this entity either had advanced disease or had been treated previously for advanced nasopharyngeal carcinoma. They had varied clinical features attributable to cerebellopontine involvement, such as sensorineural deafness, dizziness, facial palsy, and facial numbness.

CONCLUSIONS

Cerebellopontine angle involvement by nasopharyngeal carcinoma is a difficult entity, both from the diagnostic and therapeutic points of view. In high-risk patients, particularly in patients who were previously treated for advanced nasopharyngeal carcinoma, a high index of suspicion for nasopharyngeal carcinoma involvement of the cerebellopontine angle is warranted when they experience unexplained neurootologic symptoms such as sensorineural hearing loss, dizziness and facial palsy.

Diagnostic value of Epstein-Barr viral serology in nasopharyngeal carcinoma

Although Epstein-Barr virus (EBV) IgA serology has been established as an effective marker for nasopharyngeal carcinoma (NPC), it remains unclear how useful or cost-effective it is as a screening test. This article is aimed at establishing how these tests could be used most effectively in the diagnosis of NPC in an otolaryngology outpatient clinic. A total of 111 consecutive patients with NPC and an equal number of control subjects were studied. Forty-seven patients with NPC had early (AJCC stages 1 and 2) and 64 had advanced (stages 3 and 4) disease. A positive early antigen (EA) serology result was found in 81.2% of NPC patients and in none of the controls. Negative EA and viral capsid antigen (VCA) serology results were present in 2.7% of NPC patients and in 46.8% of controls. Negative EA and positive VCA serology results were found in 30.0% of NPC patients with early disease, 7.8% of NPC patients with advanced disease, and 53.2% of controls. Given its high specificity, serology for EA is recommended as a clinically useful screening test. Serology for VCA, although highly sensitive, has an unacceptably high false-positive rate, and its cost-effectiveness as a universal screening test is questionable.

Induction chemotherapy followed by concurrent chemoradiotherapy in stage III unresectable non-small cell lung cancer

The favourable experience with the combination regimen of vinorelbine, ifosfamide and cisplatin (NIP) in patients with metastatic non-small cell lung cancer (NSCLC) has led to a protocol assessing this regimen as an induction treatment in patients with stage III unresectable NSCLC, followed by thoracic radiotherapy with concurrent daily cisplatin as a radiosensitizer. Two cycles of NIP were administered 21 days apart; each cycle comprised i.v. vinorelbine 25 mg/m2 on days 1 and 8, i.v. ifosfamide 3 g/m2 on day 1 with MESNA as uroprotection, and i.v. cisplatin 50 mg/m2 on day 1. Radical thoracic radiotherapy commenced on day 43 to a total dose of 64 Gy and i.v. cisplatin 6 mg/m2 was given concurrently prior to each fraction of radiation as a sensitiser. Two more cycles of NIP were given to patients who responded favourably to the induction treatment about 2 weeks after completion of radiation. Between July 1995 and July 1997, 44 patients were treated with this protocol. This treatment schedule was generally well tolerated. Grade 3-4 neutropenia occurred in 50% of the patients and neutropenic sepsis was seen in 8. Grade 3-4 oesophagitis was uncommon. Most of the patients were able to complete the induction and concurrent chemoradiotherapy phase. Major response occurred in 75% of the patients with 2 (4.5%) complete responses (CR). A total of 6 patients achieved CR after chemoradiotherapy. At a median follow-up of 35 months, the median overall survival for all patients was 15 months with a 3-year survival rate of 24%. The median overall survival for stage IIIA patients was 19 months with a 3-year survival rate of 39% in contrast to 13 months' median overall survival and only 15% 3-year survival rate for stage IIIB. The NIP regimen results in a high response rate in NSCLC and this treatment programme seems to benefit selected patients with stage III disease.

Prediction of perinatal outcome in fetuses suspected to have intrauterine growth restriction: Doppler US study of fetal cerebral, renal, and umbilical arteries

PURPOSE

To determine and compare the diagnostic performance of fetal middle cerebral (MCA), renal (RA), and umbilical (UA) arterial Doppler ultrasonography (US) for prediction of adverse perinatal outcome in suspected intrauterine growth restriction (IUGR).

MATERIALS AND METHODS

Two hundred ninety-three small-for-gestational age fetuses (24-39 weeks at recruitment and US-estimated weight or abdominal circumference below 10th percentile) were prospectively examined with Doppler US of the UA, MCA, and RA. Clinicians were blinded to MCA and RA Doppler measurements.

RESULTS

Seventy-six fetuses (25.9%) had at least one major or minor adverse perinatal outcome. Major outcomes included stillbirth, neonatal death, neurologic complication, and necrotizing enterocolitis. The MCA pulsatility index (PI), compared with the UA PI and RA PI, was more sensitive (72.4% vs 44.7% and 8.3%) but less specific (58.1% vs 86.6% and 92.6%) in predicting adverse outcome. The UA PI had the highest positive likelihood ratio (ratio, 3.3); the MCA PI had the lowest negative likelihood ratio (ratio, 0.48). When gestational age at the first Doppler US examination was less than 32 weeks, the MCA PI had a sensitivity of 95.5% and negative predictive value of 97.7% for major adverse outcome (negative likelihood ratio, 0.10).

CONCLUSION

In suspected IUGR, while an abnormal UA PI is a better predictor of adverse perinatal outcome than an abnormal MCA or RA PI, a normal MCA PI may help to identify fetuses without major adverse perinatal outcome, especially before 32 weeks gestational age.

Prognostic factors in 677 patients in Singapore with nondisseminated nasopharyngeal carcinoma

BACKGROUND

The objective of the current study was to describe the survival of nasopharyngeal carcinoma (NPC) patients in Singapore, verify the prognostic value of the revised 1997 TNM staging system, and develop a multivariate prognostic model for NPC. In addition, the authors also examined the prognostic value of characteristics of lymph node spread and parapharyngeal involvement.

METHODS

A prospectively maintained database containing clinical and computed tomography scan data was used to reclassify 677 NPC patients treated between 1992 and 1994 according to the new staging system. Records were linked with the death registry to ascertain the patient's vital status and date of death. Overall and stage specific survival were analyzed using the Kaplan-Meier method and the log rank test. Univariate and multivariate Cox proportional hazards regression analysis were used to obtain prognostic models.

RESULTS

Two hundred seventy-four deaths (40.5%) occurred. The 5-year survival rate was 56.6% (95% confidence interval [95% CI], 52.3%, 60.7%). The stage specific 5-year survival rates were: Stage I, 88%; Stage IIA, 75%; Stage IIB, 74%; Stage III, 60%; Stage IVA, 35%; and Stage IVB, 28%. TNM stage was found to be a statistically significant prognostic factor (P < 0.0001). Cranial nerve (hazard ratio [HR]: 2.77), orbit (HR: 5.71), and intracranial involvement (HR: 2.46) conferred a particularly bad prognosis in univariate analysis. Independently significant prognostic factors were age; lymph node status; and paraoropharyngeal, cranial nerve, orbit, and nasal involvement. Among lymph node positive patients, independently significant prognostic lymph node characteristics were Ho level and laterality. Although parapharyngeal involvement appeared to be prognostically unimportant, paraoropharyngeal involvement distinguished a subgroup with a poorer prognosis (HR: 1.84; 95% CI, 1.45, 2.34; P < 0.0001). Lateral spread to the medial infratemporal fossa and beyond also was found to confer a poorer prognosis.

CONCLUSIONS

The results of the current study show that the revised 1997 TNM staging system is prognostically useful. Subdivision into paraoropharyngeal involvement and using the medial infratemporal fossa to delineate prognostically significant lateral spread should be considered in future revisions.

Concurrent chemoradiotherapy followed by adjuvant chemotherapy in Asian patients with nasopharyngeal carcinoma: toxicities and preliminary results

PURPOSE

Nasopharyngeal carcinoma (NPC) is endemic in Singapore. Nearly 60% of the patients diagnosed with NPC will present with locally advanced disease. The North American Intergroup study 0099 reported improved survival outcome in patients with locally advanced NPC who received combined chemoradiotherapy when compared to radiotherapy alone. Hence we explored the feasibility and efficacy of a similar protocol in our patients.

METHODS AND MATERIALS

Between June 1996 and December 1997, 57 patients were treated with the following schedule as described. Radical radiotherapy (RT) of 66-70 Gy to the primary and neck with cisplatin (CDDP) 25 mg/m2 on days 1-4 given by infusion over 6-8 hours daily on weeks 1, 4, and 7 of the RT. This is followed by a further 3 cycles of adjuvant chemotherapy starting from week 11 from the first dose of radiation (CDDP 20 mg/m2/d and 5-fluorouracil [5-FU] 1 gm/m2/d on days 1-4 every 28 days).

RESULTS

The majority of patients (68%) had Stage IV disease. About 54% of patients received all the intended treatment; 75% received all 3 cycles of CDDP during the RT phase and 63% received all three cycles of adjuvant chemotherapy. The received dose intensity of CDDP and 5-FU of greater than 0.8 was achieved in 58% and 60% of the patients respectively. Two treatment-related deaths due to reactivation of hepatitis B and neutropenic sepsis respectively, were encountered. At median follow-up of 16 months, 14 patients had relapsed, 12 systemically and 2 loco-regionally.

CONCLUSION

Due to the acceptable tolerability of such a protocol in our cohort of patients, we have embarked on a Phase III study to confirm the results of the 0099 Intergroup study in the Asian context.

Vinorelbine, ifosfamide and cisplatin in advanced non-small cell lung cancer

Between September 1994 and July 1997, 78 patients with advanced/metastatic, non-small cell lung cancer (NSCLC) were selected for the NIP (vinorelbine, ifosfamide, and cisplatin) protocol. The study group included 43 males; age range 34-74 years; median age 56 years; median follow-up for all patients was 14 months and for surviving patients, 30 months. Histological distribution included 55 adenocarcinomas (70.5%), 8 squamous cell carcinomas, and 9 large cell carcinomas. Stage distribution was 14 stage IIIB (malignant effusions) and 64 stage IV or recurrent metastatic; sites of metastasis were lungs, -26; liver-19; bones-27; brain-7; adrenals-3; distant nodes-2; skin-2. The NIP regimen was well tolerated by most of the patients but nausea/vomiting was noted in 55% of the cycles administered, most of them of grade 1-2 severity. Fifteen neutropenic episodes (5%) were encountered. Response to NIP was: 44 partial responses (56%); 1 complete response (1%); overall response, 58%. For stage IIIB, overall response was 36%, while for stage IV/metastatic, overall response was 63%. The median time to progression was 7 months for stage IIIB and 8 months for stage IV/metastatic disease and the overall median survival achieved was 14 months, with 60% of patients alive after one year. No significant difference in survival outcome was noted between patients with metastatic disease and those with stage IIIB (malignant effusion) disease. The NIP regimen has produced encouraging results in advanced NSCLC, as well as a favourable toxicity profile. The efficacy of NIP as a palliative tool should be assessed. A randomized trial to compare NIP with a two-drug combination of vinorelbine and cisplatin has been initiated.

Factors contributing to delayed diagnosis in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) can be difficult to diagnose. Not only is the post-nasal space (PNS) inaccessible to examination, it is frequently occupied by normal lympho-epithelium which can make differentiation from NPC difficult. Together with its frequent atypical presentation, it is not surprising that the diagnosis is missed or delayed. This is undesirable as the treatment of early NPC carries an excellent prognosis. The aim of this study is to ascertain the extent of the problem of missed or delayed diagnosis and to study the factors responsible. This was a retrospective study of all newly diagnosed patients with NPC from the Singapore General Hospital and treated in the Department of Therapeutic Radiology in the year 1996 (1 January-31 December). A total of 126 patients were studied. Eighteen patients (14.3 per cent) were found to have delayed diagnosis of more than a month. The delay ranged from 1.2 to 25 months (mean 7.2 months). Factors identified which contributed to delayed diagnosis included i) Clinicians not considering a diagnosis of NPC ii) Clinicians suspecting NPC but misled by the results of investigations iii) Patients refusing investigation or defaulting follow-up. Nearly a fifth of patients with NPC had delayed diagnosis. Many of the factors responsible for the delays appear to be preventable by better patient education and counselling, doctors having sharper clinical acumen and skills in NPC diagnosis and the hospital administration having a system of tracking down high risk patients who default.

Concurrent chemoradiotherapy in patients with locally advanced nasopharyngeal carcinoma of the undifferentiated type

The result with radiotherapy alone in patients with locally advanced nasopharyngeal carcinoma (NPC) was disappointing. Encouraging results have been reported with the use of concurrent chemoradiotherapy in patients with locally advanced squamous cell carcinoma of the head and neck. Hence, we decided to explore the use of this treatment schedule in patients who presented with locally advanced disease (UICC/AJCC classification system). Between July 1995 and March 1996, 14 patients with locally advanced NPC were treated with the following schedule: radiation therapy was given conventionally to a total of 66 to 70 Gy to both the nasopharynx and neck with or without parapharyngeal/intracavitary boost; chemotherapy consisted of intravenous cisplatin at 20 mg/m2/day and intravenous 5-flurouracil 1000 mg/m2/day, infused over 8 hours on days 1 to 4 during the first and fifth week of radiation therapy. Depending on the patient's tolerability and clinical assessment of toxicity, a third cycle of chemotherapy was planned 4 to 5 weeks after the second cycle, upon the completion of the radiotherapy. Twelve patients completed all intended treatment. Two patients failed to do so due to treatment-related mortality. The median follow-up duration was 30 months. Limiting toxicities were myelosuppression and oropharyngeal mucositis. The overall response rate was a 100% at both the primary and nodal sites of disease. The median disease-free survival was 21 months. Forty per cent of the patients were alive at 3 years. This treatment schedule was associated with an unacceptable treatment-related death rate. As a result, this protocol was terminated.

The pattern of nodal recurrence following definitive radiotherapy for nasopharyngeal carcinoma

BACKGROUND

The pattern of nodal metastasis in previously untreated nasopharyngeal carcinoma (NPC) has been studied and reported. In order to analyse the pattern of recurrent nodal disease in previously treated NPC, a retrospective study on 68 patients who underwent radical neck dissection for regionally recurrent NPC was conducted.

METHODS

Seventy-four neck dissections were performed on 68 patients who developed nodal recurrence after a mean disease-free interval of 39.2 months. None of the patients had evidence of local or systemic disease at the time of surgery. Histopathological reports of the 74 neck dissections were analysed with regard to the number of positive nodes as well as the number of involved nodal levels.

RESULTS

Of the 65 neck dissection specimens with analysable data, 31 showed metastatic disease at a single nodal level with a mean number of positive nodes of 1.2, while 34 showed metastatic disease at multiple levels with a mean number of positive nodes of 6.6. Nodal recurrence occurred at level II with the greatest frequency (78.5%). Of the 31 specimens with single level nodal involvement, 21 (67.7%) occurred at level II. Isolated involvement at the other levels did occur, but was uncommon (range 3-16%). Of the 34 specimens with multiple level nodal involvement, 30 (88.2%) showed involvement at level II. Once more than one level was involved, the frequency of involvement at any given level was at least 30%.

CONCLUSION

The predominant involvement at level II and the high frequencies of involvement at all levels support the use of a classical radical neck dissection in treating recurrent nodal disease in NPC.

Phase II trial of a paclitaxel and carboplatin combination in Asian patients with metastatic nasopharyngeal carcinoma

PURPOSE

An earlier phase II trial of paclitaxel in patients with metastatic nasopharyngeal carcinoma (NPC) demonstrated a response rate of 22%. Hence we proceeded to study the combination of paclitaxel and carboplatin in these patients.

PATIENTS AND METHODS

The 21-day regimen was as follows: i.v. paclitaxel 175 mg/m2 over three hours preceded by standard premedications, followed by i.v. carboplatin dosed at AUC of six infused over one hour. Only chemotherapy-naive patients with histological diagnoses of undifferentiated carcinoma of the nasopharynx, systemic metastases and radiologically measurable lesions were eligible.

RESULTS

Thirty-two patients were accrued to this study. Twenty patients (62%) had at least two sites of metastasis. The main grade 3-4 toxicity was neutropenia (31%). Nine patients (28%) developed neutropenic sepsis, which caused the demise of one of them. Twenty-four patients (75%) responded to treatment, with one (3%) attaining a complete response. The median time to progression of disease was seven months and the median survival was 12 months. At one year, 52% of the patients were alive.

CONCLUSIONS

The combination of paclitaxel and carboplatin is an active regimen in NPC. Its convenience of administration and good tolerability make it an attractive alternative regimen to consider for patients with metastatic disease.

A novel nonmetallized tip for electrospray mass spectrometry at nanoliter flow rate

We report the fabrication of a durable nonmetallized nanospray tip. This nanospray tip does not require complex preparation procedures such as chemical treatment, deposition of gold or SiOx vapor. It was fabricated by pulling a heated glass capillary of 1.1 mm internal diameter to produce a fine tip with an orifice of 10-15 microns in diameter. A 10 microns gold-plated tungsten wire was inserted through the capillary tip. This tungsten wire played a central role in the operation of this durable nanospray tip by providing electrical contact. This type of nanospray tip could withstand electrical discharges and sustained spraying of solution at nanoliter flow rate for more than 3 h. Using insulin (35 microM) and myoglobin (1 microM) solutions, useful mass spectrum could be acquired with low fmol sensitivity.

Long-term post-irradiation middle ear effusion in nasopharyngeal carcinoma

This study aimed to find out if there were factors which influenced the development of long-term middle ear effusion (MEE) in patients irradiated for nasopharyngeal carcinoma. Thirty-five patients (70 ears) were studied for 2-8 years (mean 5.5 years) post-radiotherapy. The factors studied were (a) sex (b) age (c) tumour size and (d) presence of pre-radiotherapy MEE. Only the presence of pre-radiotherapy MEE was found to be statistically significant (P = 0.004, Fisher's exact test). Stepwise multiple regression analysis showed the presence of pre-radiotherapy MEE was a predictor of post-radiotherapy MEE with an odds ratio of 0.67. It is postulated that irreversible Eustachian tube dysfunction occurs when the tube which has been damaged by tumour is further damaged by irradiation. This may explain the frequent persistent otorrhea when ventilation tubes are used to treat post-radiotherapy MEE in patients with nasopharyngeal carcinoma. In conclusion, an ear with pre-irradiation MEE was almost seven times more likely to have long-term post-irradiation MEE than an ear without pre-irradiation MEE.

Long-term hearing status after radiotherapy for nasopharyngeal carcinoma

This paper evaluates the hearing status in the long-term, of patients who have had radiotherapy for nasopharyngeal carcinoma (NPC) and also discusses the hearing losses from a disability point of view, which takes into account binaural hearing. Forty patients who have had NPC successfully treated by a single radical course of radiotherapy of 70-80 Gy were studied at 2-12 years (mean 6.2 years) after radiotherapy. Each patient was examined clinically and with a pure-tone audiogram. Averaged hearing thresholds over 0.5, 1.0, 2.0 and 4.0 kHz were evaluated and a value > 30 dB was considered abnormal. The findings were compared with age-matched controls. The median hearing threshold for each ear in NPC patients was found to be 31.9 dB (range 10.0-86.3 dB) and that for controls 17.5 dB (7.5-38.8 dB) (P < 0.0005, Wilcoxon's matched pairs test). In NPC patients, 44 ears (55.0%) had abnormal hearing, of which 17 (21.3%), 5 (6.3%) and 22 (27.5%) ears had predominantly sensori-neural, conductive and mixed hearing losses, respectively. Nineteen ears had middle ear effusions, accounting for the majority of mixed and conductive hearing losses. In terms of individual patients, 8 (20.0%) and 18 (45.0%) patients had abnormal hearing in one year (monaural hearing disability) and both ears (binaural hearing disability), respectively. In conclusion, a substantial proportion of patients who have had radiotherapy for NPC, have hearing disability in the long-term, as compared to normal controls.

Intrathecal methotrexate overdose

We report two cases of intrathecal methotrexate overdose. A 3-y-old girl with acute lymphoblastic leukaemia and a 4-y-old boy with Burkitt's lymphoma were to receive an intrathecal injection of methotrexate after completion of intravenous methotrexate infusion. Instead of 12.5 mg, they both received a dose of 125 mg. Both children developed generalized convulsion 3 h after the overdose, but afterwards recovered completely. Intravenous folinic acid and dexamethasone rescue were employed, but no attempt was made to exchange the cerebrospinal fluid. In addition to the staff's failure to check the drug label carefully, the marked resemblance of the two dose preparations of methotrexate (50 mg/5 ml and 500 mg/5 ml) may have been contributory.

Localised nodal non-Hodgkin's lymphoma--a study of 42 cases treated by radiotherapy

The records of 42 patients with stage I and II nodal non-Hodgkin's lymphoma treated by radiotherapy with and without chemotherapy were analysed with regards to clinical presentation, investigations, treatment, radiotherapy techniques and results. The 5-year overall survival rates for all, low grade, intermediate grade and high grade histology types are 69.5%, 100%, 64.4% and 46.9% respectively. The 5-year relapse-free survival rates of those treated by initial radiotherapy alone for all, low grade and intermediate-high grade histology types are 54.8%, 46.9% and 59.4% respectively.

Patient profile and survival in 270 computer tomography-staged patients with nasopharyngeal cancer treated at the Singapore General Hospital

This is a report analysing the patient profile and survival results in 270 patients with nasopharyngeal carcinoma treated with radiation therapy between July 1987 and December 1988. The patients had a median age of 52.6 months, and a male-female ratio of 2.5:1. Ninety-four percent of patients were Chinese. The commonest presentation was that of a neck mass (found in approximately 65% of patients). Approximately two-thirds presented with disease more advanced than Ho's stage II. At a median follow-up of 52.6 months, the 5-year actuarial survival rate was 53% and the freedom from relapse rate was 57%. One hundred and seven patients died within the observation period. Of these, 46 patients had disease in the post nasal space, 41 in the neck and 60 in sites outside the head and neck.

Hearing disability before and after radiotherapy for nasopharyngeal carcinoma

This paper evaluates post-irradiation hearing changes in patients with nasopharyngeal carcinoma (NPC) from a disability orientated approach, which takes into account binaural hearing. Newly diagnosed patients with NPC were studied before radiotherapy, and at four to 12 months (mean 9.2 months) after radiotherapy, provided they remained disease-free. Each patient was examined clinically and with pure tone audiograms. Tympanometry was used to confirm middle ear effusion. Averaged hearing thresholds over 0.5, 1 and 2 kHz were evaluated. If abnormal (> 30 dB), the resultant hearing disability was illustrated by a modified Glasgow Plot. Twenty-three males and 10 females completed the study. Middle ear effusions resulted in 39.3 per cent (binaural in two patients) and 33.3 per cent (binaural in five patients) of patients having hearing disability pre- and post-irradiation respectively. No patient had hearing disability as a result of a sensorineural loss. It is recommended that future reporting of post-irradiation hearing changes in patients with NPC, as in middle ear surgery, be considered from a disability-orientated approach.