Associations between patient-level health literacy and diagnostic time intervals for head and neck cancer: A prospective cohort study

BACKGROUND

Health literacy (HL) comprises skills and knowledge required to understand, access, and make decisions about healthcare. Our aim was to examine associations between patient HL and time intervals (defined in the Aarhus statement) along the pathway to treatment of head and neck cancer (HNC).

METHODS

A prospective cohort study was conducted from October 2018 to March 2020. Participants completed the Health Literacy Questionnaire (HLQ®) and described key events and dates along the pathway to treatment using validated questionnaires. Correlations between six diagnostic time intervals and domains of HL were explored, and factors predicting exceeding maximum acceptable timeframes were assessed using logistic regression.

RESULTS

One hundred patients with a diagnosis of HNC within the preceding 6 months were recruited. HLQ® Domain 2 (sufficient information to manage health) was significantly negatively associated with four intervals: the patient interval (first symptom to first presentation), primary care interval (first presentation to referral to secondary care), diagnostic interval (first presentation to diagnosis), and total interval (first symptom to treatment onset); correlation coefficients -0.25 to -0.27 (P < 0.05). Domain 8 (ability to find good information) was significantly negatively associated with three intervals (primary care interval, diagnostic interval, and total interval; correlation coefficients -0.23 to -0.34; P < 0.05). Higher education, age, and comorbidity levels were associated with shorter patient and diagnostic intervals.

CONCLUSIONS

HL may be a potential target to improve timeliness of HNC diagnosis and reduce disparities in outcomes.

First Phase Development of a Patient-reported Outcome Measure for Midface Oncology

Background

Facial cancer surgery involving the midface (comprising the lower eyelids, nose, cheeks, and upper lip) can have debilitating life-changing functional, social, and psychological impacts on the patient. Midface symptoms are inadequately captured by existing patient-reported outcome measures (PROMs). PROMs are increasingly used for individual patient care, quality improvement, and standardized reporting of treatment outcomes. This study aimed to present our findings from the first phase of the development of a midface, specifically periocular and nasal, PROM.

Methods

After international guidance for PROM development, the first phase comprised identification of salient issues and item generation. Fifteen patients who had midface surgery and 10 clinicians from various specialties with more than 5 years' experience treating these patients were recruited. Semi-structured interviews explored aesthetic, functional, social, and psychological outcomes, with specific attention to deficiencies in current PROMs. Thematic analysis was used to develop an item pool, and group interviews with clinicians were carried out to create and refine PROM scales.

Results

Qualitative data from patient interviews were grouped into aesthetic, functional, and psychosocial domains for the eyelids and nose. Ninety-nine draft items were generated across these domains. Following focus group discussions, the final version of the midface-specific PROM contained 31 items (13 eye-specific, 10-nose-specific, eight general midface items).

Conclusions

This midface-specific PROM is valuable in assessing and comparing patient-reported outcomes in those who have undergone complex resection and reconstruction of the midface. This PROM is currently undergoing field testing.

When should patients with T1N0 oral squamous cell carcinoma be considered for elective neck dissection?

AIMS

To identify adverse pathological features (APF) predicting nodal failure in clinically node negative T1 oral squamous cell carcinoma (OSCC).

METHODOLOGY

This study evaluated patients with T1N0 (≤5 mm depth of invasion (DOI) and ≤2 cm diameter) oral cancers from a prospectively maintained database between 1988 and 2020. All patients underwent surgical excision of the primary lesion without neck dissection. Patients underwent three monthly clinical surveillance and salvage neck dissection was performed if nodal relapse was diagnosed.

RESULTS

Overall, 141 patients were included. Nodal relapse was reported in 16/141 (11.3%) patients. Factors impacting regional recurrence-free survival were DOI ≥3 mm (HR: 2.4, P < 0.001), maximum tumour diameter ≥12 mm (HR: 1.1, P = 0.009), perineural invasion (PNI) (HR 7.5, P = 0.002) and poor differentiation (HR 5.3, P = 0.01). Rates of nodal relapse increased from 2% amongst patients with no APFs to 100% for those with four APFs. Patients with two or more APFs had significantly poorer 5-year regional recurrence-free survival (94.8% vs. 56.3%, P < 0.001).

CONCLUSION

Patients with T1N0 OSCC with two or more APFs (DOI ≥3 mm, diameter ≥12 mm, PNI or poor differentiations) should be considered for elective neck dissection.

Patient-reported experiences and satisfaction with head and neck surgery outreach clinics in regional New South Wales, Australia: A cross-sectional survey

RATIONALE

Head and neck surgery services are increasingly being centralised in Australia. Outreach models can overcome burdens of travel that patients in regional and rural areas experience when attending routine appointments, by providing services closer to home.

AIM

To explore patient-reported experiences and satisfaction with regional outreach services for head and neck surgery in Australia.

METHODS

Patients who attended two regional outreach clinics in New South Wales (NSW), Australia, were surveyed over a 6-month period. Patients completed the Outpatient Cancer Clinics Survey (2020 version) that explored perceptions and experiences of the clinic. Patients with cancer were asked to complete the Edmonton Symptom Assessment System and the Communication and Attitudinal Self-Efficacy scale. Descriptive statistics and analysis of data was performed, and results were compared to the NSW statewide Outpatient Cancer Clinics Survey (2020). Content analysis of free text responses was performed.

RESULTS

Some 128 patients responded (56% response rate; mean age 67.2 years, 46.1% female). Compared to the 2020 NSW survey, a higher proportion of patients in our cohort responded positively to 14 of the 26 questions, with the greatest differences observed for questions regarding waiting area comfort (+12.1%, p = 0.008), being informed about different treatment options (+9.5%, p = 0.04), and issues relating to parking (+9.5%, p = 0.03). A lower proportion of our sample responded positively to the question about whether health professionals knew enough about their medical history (-19.3%, p < 0.001). Respondents appreciated having a local clinic that helped them avoid travel to major cities and associated expenses and highlighted benefits of expert consultation and timeliness of investigations. However, cost of appointments and level of reimbursements remain barriers for some patients.

CONCLUSIONS

Patients had a high level of satisfaction with regional outreach clinics for head and neck surgery across most domains, indicating patients highly value this service.

The Utility of Near-Infrared Autofluorescence for Parathyroid Gland Identification During Thyroid Surgery: A Single-Center Experience

Parathyroid gland injury during thyroid surgery is common and can lead to postoperative hypocalcemia. This study aims to determine the utility of near-infrared autofluorescence (NIRAF) technology for parathyroid gland identification in thyroid surgery. A prospective case series of patients who underwent thyroid surgery between March and June 2021 were examined. Following intra-operative visualisation, parathyroid glands and surrounding tissues were exposed to near-infrared light with a wavelength of approximately 800 nm using the Storz® Near-Infrared Range/Indocyanine Green (NIR/ICG) endoscopic system. Parathyroid glands were expected to show autofluorescence following exposure. Twenty patients who underwent thyroid surgery were included. Eighteen patients (90%) were female, with a median age of 50.0 (IQR 41.0 - 62.5). Surgeries performed include hemithyroidectomy (9 patients; 45.0%), total thyroidectomy (8 patients; 40.0%), completion thyroidectomy (2 patients; 10.0%) and right inferior parathyroidectomy (1 patient; 5.0%). Attempts were made to identify 56 parathyroid glands in this case series. There were 46/56 (82.1%) surgeon-identified parathyroid glands through direct visualisation. Using NIRAF technology, 39/46 (84.8%) were identified as parathyroid glands. There was no inadvertent resection of parathyroid glands or post-operative hypocalcaemia. NIRAF technology has the potential to be a useful tool in confirming the presence of parathyroid glands following direct visualisation intra-operatively.

Comparative analysis of pre-operative ultrasound and histopathology in small papillary thyroid carcinoma in the era of active surveillance

BACKGROUND

Contemporary management of small papillary thyroid carcinomas (PTC) includes active surveillance (AS) as a number of these tumours are indolent. Overseas studies have reported AS in tumours up to 15 mm. This study aims to look at an Australian cohort of patients who have had surgery for non-incidental PTCs and analyse their pre-operative ultrasound and histopathology data to investigate potential issues that might arise in the era of AS.

METHODS

Retrospective review of 82 patients who had surgical removal of PTCs ≤15 mm in diameter. Pre-operative ultrasound imaging was reviewed by an experienced sonologist and histopathology data was obtained from medical records. The AS risk stratification framework by Brito et al. was used to determine those who were feasible for AS based on ultrasound findings.

RESULTS

Review of pre-operative ultrasounds demonstrated there were 68 (82.9%) patients who were shown to be either appropriate or ideal for AS. On review of histopathology, 49 (69%) patients had at least one adverse pathological risk factor. This is more than half of the patients that were originally identified as candidates for AS.

CONCLUSION

Our study has revealed a large proportion were suitable for AS but when compared with histopathological guidelines there was a high incidence of adverse pathological features found. This discrepancy indicates that although the guidelines are important, there are unknown pathological variables that need to be considered in patients selected for AS.

Anterolateral thigh, radial forearm and superficial circumflex iliac perforator flaps in oral reconstruction: a comparative analysis

BACKGROUND

Anterolateral thigh (ALT) and Radial forearm free flaps (RFFF) are historically the most common methods of oral reconstruction. The Superficial circumflex iliac artery perforator flap (SCIP) is an alternative providing a donor site that can be readily closed primarily with improved cosmesis in younger patients, due to its concealability.

METHODS

We reviewed 135 patients who received ALT, RFFF or SCIP flaps for oral reconstruction in our institution. Our aim was to compare operative and perioperative outcomes between each cohort. ANOVA and χ² test were used for statistical analysis.

RESULTS

There were 37 ALT, 64 RFFF and 35 SCIP reconstructions. Patients reconstructed with SCIP flaps had smaller resection volumes (P < 0.001) and earlier T and N classifications (P = 0.001, P = 0.008), and consequently reduced tracheostomy rates (P < 0.001), reduced need for enteral feeding at discharge (P < 0.001) and shorter length of stay and perioperative times (P < 0.001). SCIP flaps were more common in younger patients (P < 0.01). ALT flaps were used for more advanced disease (P = 0.001) and had larger resection volumes (P < 0.001) and increased need for assisted enteral feeding (P < 0.001). There were no significant differences in flap or donor site outcomes. There were two flap failures, both RFFF.

CONCLUSION

Each flap plays an important role in the reconstruction of oral defects, with larger defects preferentially reconstructed with ALT flaps. SCIP appears to be a reliable alternative in small defects with excellent perioperative and postoperative outcomes.

ADMANI: Annotated Digital Mammograms and Associated Non-Image Datasets

Supplemental material is available for this article. Keywords: Mammography, Screening, Convolutional Neural Network (CNN) Published under a CC BY 4.0 license. See also the commentary by Cadrin-Chênevert in this issue.

Survival outcomes of perineural spread in head and neck cutaneous squamous cell carcinoma

AIM

To present an institution's experience and survival outcomes for patients with head and neck cutaneous squamous cell carcinoma (HNcSCC) and perineural spread (PNS).

METHOD

Retrospective study of patients with HNcSCC and PNS treated between January 2010 and August 2020 from the Sydney Head and Neck Cancer Institute database, Sydney, Australia; a high-volume, tertiary, academic head and neck centre. Patient demographics, primary site, involved cranial nerves, treatment modality, loco-regional failure and survival data were obtained.

RESULTS

Forty-five patients were identified, of which 32 patients were male (71%). Mean age at diagnosis was 68.7 years (range 43-90). Median follow-up was 16.1 months (range 1-107). The trigeminal nerve was most frequently involved (n = 30, 66.6%) followed by facial nerve (n = 13, 28.9%). Most patients underwent surgery followed by radiotherapy (n = 33, 73%) and eight received definitive radiotherapy. The median overall survival (OS) was 4.5 years (95% CI 3.71-5.38), median disease-specific survival 5.1 years (95% CI 4.21-5.97) and median disease-free survival (DFS) was 1.7 years (95% CI 1.11-2.22). The estimated 5-year OS and DFS were 45% and 25%, respectively. Patients treated with surgery and adjuvant radiotherapy with a clear proximal nerve margin had favourable DFS (P = 0.035) and trended towards better OS (P = 0.134) compared with patients with an involved nerve margin. Patients treated surgically with involved proximal nerve margins had similar outcomes compared with patients with treated definitive radiotherapy (HR 0.80, 95% CI 0.29-2.22, P = 0.664).

CONCLUSION

The likelihood of achieving a clear proximal nerve margin should be a strong consideration in the selection of appropriate patients for primary surgery.

Benchmarking Survival Outcomes Following Surgical Management of pT3 and pT4 Cutaneous Squamous Cell Carcinoma of the Head and Neck

Background

pT3/4 head and neck cutaneous squamous cell carcinomas (HNcSCCs) are associated with poor outcomes, including local recurrence, metastasis and death. Whilst surgery remains the standard treatment for advanced HNcSCC, novel systemic therapies, such as immunotherapy, are being used earlier in the treatment paradigm. It is imperative that the clinical outcomes of surgery are clearly described so that conventional and emerging treatment modalities can be better integrated and sequenced in the management of pT3/4 HNcSCC.

Methods

Patients with confirmed pT3/4 HNcSCC undergoing curative surgical resection between 2014-2020 were identified retrospectively from a prospectively maintained research database. The primary outcomes of interest were locoregional control (LRC), disease-specific survival (DSS), and overall survival (OS). The secondary outcome was surgical complication rate.

Results

A total of 104 patients (median age 74, range 41–94 years) were included, 90% of which had pT3 tumors; 36.5% received adjuvant radiotherapy. Median follow-up was 24.3 (range 1.0–84.3) months. LRC at 5 years was 62.0%, DSS at 5 years was 83.7%, and OS at 5 years was 71.9%. Median time to recurrence was 8.4 months. LRC was reduced in the presence of margin involvement and previous treatment (radiotherapy/surgery). The major surgical complication rate was 9.6%.

Conclusions

More than 60% of patients treated surgically for pT3/4 head and neck cSCC were alive and free of disease at 5 years posttreatment. High-risk features such as margin involvement and having had previous treatment (radiotherapy/surgery) should be used to guide adjuvant therapy.

Retina Injury After Dexamethasone Injection Into a Vitrectomized Eye

Purpose:

This work reports a case of retinal and vitreous hemorrhage after a dexamethasone (Ozurdex, Allergan) intravitreal implant injection to treat clinically significant macular edema (ME) in a patient with moderate nonproliferative diabetic retinopathy.

Methods:

A 61-year-old woman who had a vitrectomy 3 years prior in the right eye underwent intravitreal dexamethasone implant injection in the right eye. Immediately after the injection, the patient noted numerous floaters, with visual acuity decline from 20/30 before injection, to counting fingers at 3 feet after injection. Dilated examination revealed the dexamethasone implant resting against the retina, just inferior to the inferior arcade. On 360° fundus examination, the retina was found to be flat and attached. Optical coherence tomography of the macula demonstrated that the dexamethasone implant was preretinal, possibly having lifted the internal limiting membrane.

Results:

Thirty minutes after the injection, the patient reported that her vision was starting to clear. The patient was informed about what had transpired and warned about signs and symptoms of retinal detachment. She canceled her 1-week follow-up appointment because her vision returned to baseline. By 4 weeks post injection, her vision was 20/20 without macular edema.

Conclusions:

This case represents the first reported instance in which retinal impact by an Ozurdex implant was observed without treatment and vision recovered to baseline.

Application of salivary noncoding microRNAs for the diagnosis of oral cancers

Oral cancer is on the rise globally and survival rates, despite improvements in clinical care, have not significantly improved. Early detection followed by immediate intervention is key to improving patient outcomes. The use of biomarkers has changed the diagnostic landscape for many cancers. For oral cancers, visual inspection followed by a tissue biopsy is standard practice. The discovery of microRNAs as potential biomarkers has attracted clinical interest but several challenges remain. These microRNAs can be found in bodily fluids such as blood and saliva which have been investigated as potential sources of biomarker discovery. As oral cancer is localized within the oral cavity, saliva may contain clinically relevant molecular markers for disease detection. Our review provides an outline of the current advances for the application of salivary microRNAs in oral cancer. We also provide a technical guide for the processing of salivary RNAs to ensure accurate clinical measurement and validation.

Replication and extension of a model predicting response to psilocybin

BACKGROUND

Recent research demonstrated the potential of psychedelic drugs as treatment for depression and death-related anxiety and as an enhancement for well-being. While generally positive, responses to psychedelic drugs can vary according to traits, setting, and mental state (set) before and during ingestion. Most earlier models explain minimal response variation, primarily related to dosage and trust, but a recent study found that states of surrender and preoccupation at the time of ingestion explained substantial variance in mystical and adverse psilocybin experiences.

OBJECTIVES

The current study sought to replicate the previous model, extend the model with additional predictors, and examine the role of mystical experience on positive change.

METHOD

A hierarchical regression model was created with crowdsourced retrospective data from 183 individuals who had self-administered psilocybin in the past year. Scales explored mental states before, during, and after psilocybin ingestion, relying on open-ended memory prompts at each juncture to trigger recollections. Controlled drug administration was not employed.

RESULTS

This study replicated the previous model, finding a state of surrender before ingestion a key predictor of optimal experience and preoccupation a key predictor of adverse experience. Additional predictors added to the explanatory power for optimal and adverse experience. The model supported the importance of mystical experiences to long-term change.

CONCLUSION

Mental states of surrender or preoccupation at the time of ingestion explain variance in mystical or adverse psilocybin experiences, and mystical experiences relate to long-term positive change. The capacity to recognize this optimal preparatory mental state may benefit therapeutic use of psilocybin in clinical settings.

Acetazolamide: A New Treatment for Visual Vertigo

Visual vertigo is a disorder characterised by symptoms of dizziness, vertigo, unsteadiness, disorientation, and general discomfort induced by visual triggers. It is currently treated with vestibular rehabilitation therapy, with no effective pharmacotherapy available for treatment-resistant cases. The objective of this study was to evaluate the efficacy of oral acetazolamide in improving symptoms of visual vertigo. A comparative case series of adult patients clinically diagnosed with visual vertigo was conducted from January 1992 to May 2015. Patients without a full neurologic or otorhinolaryngologic work-up, negative magnetic resonance imaging (MRI), and an organic cause for their symptoms were excluded. The identified patients were then contacted by phone to complete a voluntary symptom survey. Main outcome was the subjective reported percentage in symptom improvement. Secondary outcomes were subjective improvement by symptom triggers. The participants were retrospectively divided into three groups based on their treatment with acetazolamide: currently on acetazolamide, terminated acetazolamide, or never initiated acetazolamide. Fifty-seven patients met the inclusion criteria and were willing to complete the phone survey (19 currently on acetazolamide, 27 terminated acetazolamide, and 11 never initiated therapy). Overall symptomatic improvement was reported by 18 (94.7%) patients currently on acetazolamide, 18 (66.7 %) who terminated acetazolamide, and 5 (45.5%) who never initiated therapy, varying significantly by group (p = 0.0061). Greatest improvement was reported in symptoms triggered by being a passenger in a car. These results show that acetazolamide has a positive association with improvement of symptoms of visual vertigo.

Prognostic implications of lymph node yield and lymph node ratio in papillary thyroid carcinoma

BACKGROUND

The lymph node yield (LNY) and the lymph node ratio (LNR) have been shown to be important prognostic factors in oral, colon, and gastric cancers. The role of the LNY and LNR in papillary thyroid cancer (PTC) is unclear. The aims of this study were to determine if a high LNR and a low LNY decrease disease-free survival rates. This study further aimed to determine an optimum nodal yield.

METHODS

A retrospective analysis was conducted of 198 patients with PTC undergoing total thyroidectomy with neck dissection between 1987 and 2011. The LNY and LNR were adjusted by relevant covariates in a multivariate Cox regression analysis with Andersen-Gill extension.

RESULTS

The LNR was associated with a decrease in disease-free survival (hazard ratio 3.2 [95% confidence interval 1.4-7.3], p=0.005). Patients with an LNR of 0.30 or higher had a 3.4 times higher risk of persistent or recurrent disease compared with patients with an LNR of 0.00 ([95% confidence interval 1.1-10.5], p=0.031). Conversely, patients with an LNR of 0.11 or lower had an 80% chance of remaining disease free during 5 years of follow-up. The LNY showed no significant independent effect and an optimum nodal yield was not determined.

CONCLUSIONS

The LNR is an important independent prognostic factor in PTC and can be used in conjunction with existing staging systems. A clinical relevant cut-off point of 0.3 (one positive lymph node out of three total) is proposed. No prognostic implications for LNY were identified.

The prognostic and staging implications of bone invasion in oral squamous cell carcinoma

BACKGROUND

A study was undertaken to determine whether bone invasion is an independent prognostic factor in oral squamous cell carcinoma (SCC) after taking into account the extent of bone invasion.

METHODS

The study was a retrospective review of 498 patients with oral SCC undergoing surgery with curative intent, 102 of whom had pathologically proven bone invasion. Bone invasion was categorized as absent, cortical, or medullary and tested for association with disease control and survival.

RESULTS

After adjusting for potential confounding factors in multivariate analysis, there was no association between cortical invasion and overall (P = .48) or disease-specific survival (P = .63). In contrast, medullary invasion was an independent predictor of reduced overall (hazard ratio [HR], 1.9; 95% confidence interval [CI], 1.2-3.1; P = .006) and disease-specific survival (HR, 2.1; 95% CI, 1.2-3.6; P = .01), and this appeared to result from an increased risk of distant metastatic failure (P = .037) rather than local (P = .51) or regional recurrence (P = .14). Within the subset of patients with medullary invasion, survival differed significantly according to tumor size (P = .029).

CONCLUSIONS

Patients with oral SCC and bone invasion have widely variable outcomes depending on the depth of bone invasion and tumor size. The results suggest that the current American Joint Committee on Cancer staging system, which classifies all tumors invading through cortical bone as T4, has limited prognostic utility. The authors recommend a revision of the T staging system such that tumors are classified as T1 to T3 based on size and then upstaged by 1 T stage in the presence of medullary bone invasion.

Vesicular glutamate transporter and cognition in stroke: a case-control autopsy study

OBJECTIVES

Vascular dementia (VaD) accounts for approximately 15%-20% of all dementias, but the relationship of progressive cognitive impairment to neurochemical changes is poorly understood. We have therefore investigated glutamatergic synaptic markers in VaD.

METHODS

We used homogenates prepared from gray matter from 2 neocortical regions (Brodmann area [BA] 9 and BA 20) and Western blotting to determine the concentrations of key components of the glutamatergic neurotransmitter system, vesicular glutamate transporter 1 (VGLUT1) and excitatory amino acid transporter EAAT2 (GLT-1), and the ubiquitous synaptic protein, synaptophysin, in 73 individuals-48 patients with cerebrovascular disease with and without dementia, 10 patients with AD, and 15 controls-in a case-control design.

RESULTS

VGLUT1 concentrations in BA 20 and BA 9 were correlated with CAMCOG total (Rs 0.525, p = 0.018, n = 20; Rs 0.560, p = 0.002, n = 27) and CAMCOG memory scores (Rs 0.616, p = 0.004, n = 20; Rs 0.675, p = 0.000, n = 27). VGLUT1 concentration in BA 9 differed between the different dementia groups and the stroke no dementia group (1-way analysis of variance F = 6.69, p = 0.001 and Bonferroni p < 0.01 in each case), with subjects with stroke who did not develop dementia exhibiting the highest mean value for VGLUT1.

CONCLUSIONS

These data suggest that loss of glutamatergic synapses is a feature of VaD and Alzheimer disease but the preservation of synapses, in particular glutamatergic synapses, in the frontal cortex against the temporal cortex plays a role in sustaining cognition and protecting against dementia following a stroke.

Role of thyroidectomy in advanced laryngeal and pharyngolaryngeal carcinoma

OBJECTIVE

Total thyroidectomy (TThy) or hemithyroidectomy (HThy) in conjunction with a total laryngectomy (TL) or pharyngolaryngectomy (PL) for laryngeal carcinoma often results in hypothyroidism requiring life-long thyroid hormone replacement. The aims were to determine the incidence of thyroid gland (TG) invasion in patients undergoing TL or TPL with TThy or HThy for laryngeal or hypopharyngeal carcinoma and to assess predicative factors.

STUDY DESIGN

Case series with chart review.

SETTING

Guy's Hospital, London, UK.

SUBJECTS AND METHODS

Thirty-five patients from 2004 to 2008 were reviewed. Specimens were examined to determine the incidence of TG invasion and predicative factors. Preoperative imaging was reviewed to assess the radiological evidence of TG invasion.

RESULTS

TL and TThy were performed in 19 patients, TL and HThy in three patients, and PL and TThy in 13 patients. Surgery was performed for primary and recurrent carcinoma in 28 and eight patients, respectively. Histological evidence of invasion of the TG was found in three patients (8.5%). No significant relationship was found between TG invasion and patient's sex, subsite of primary carcinoma, stage of primary disease at surgery, degree of differentiation, or the presence of subglottic extension. In addition, no significant relationship was found between the presence of TG invasion and recurrent disease. Definite evidence of radiological invasion of the TG was seen in only one patient.

CONCLUSIONS

Invasion of the TG in patients undergoing TL or TPL is a rare event and limits the need for TThy in most cases.

Queuosine modification of tRNA: a case for convergent evolution

Queuosine is a hypermodified nucleoside found in position 34, the anticodon wobble position, of four tRNA species. This modification is distributed with near uniformity across all life forms found on this planet. Yet the molecular mechanisms involved with accomplishing this ubiquitous posttranscriptional modification of tRNA are dramatically different between prokaryotic and eukaryotic organisms, which suggests that these were formed by convergent evolution of a fundamental life process essential to nearly all life forms. This minireview describes the differences between these modification systems and points to a new direction for developing research on the molecular function queuosine-modified tRNA in diverse species.

Determination of queuosine modification system deficiencies in cultured human cells

Queuosine-deficient tRNAs are often observed in neoplastic cells. In order to determine possible sites for malfunction of the multistep queuosine modification system, comprehensive studies were performed on two human neoplastic cell lines, the HxGC(3) colon adenocarcinoma and the MCF-7 breast adenocarcinoma, which are 100 and 50-60% queuosine deficient, respectively. These results were compared with data obtained from normal human fibroblast (HFF) cultures which maintain 100% queuosine-modified tRNA populations. Queuine uptake in all three cell types was similar and each demonstrated activation by protein kinase C (PKC). However, incorporation of queuine into tRNA by tRNA:guanine ribosyltransferase (TGRase; E.C. 2.4.2.24) and PKC-catalyzed activation of this enzyme occurred only in HFF and MCF-7 cells. The HxGC(3) cell line exhibited no TGRase activity as was expected. Treatment with 5-azacytidine (5-azaC) induced TGRase activity to a level 20% of that in HFF and MCF-7 cells; however, this 5-azaC-induced TGRase activity was not regulated by PKC. Salvage of the queuine base from tRNA degradation products has been shown in mammalian cells and was measured in the HFF cells. However, salvage activity in the MCF-7 cell line was deficient. Therefore, it was shown by direct measurements that the HxGC(3) cell line is completely lacking in queuosine-modified tRNA due to loss of functional TGRase, while the MCF-7 cell line has an inefficient queuine salvage mechanism resulting in a significant deficiency of queuosine-modified tRNA. These techniques can be applied to any cultured cell types to determine specific lesions of the queuosine modification system, which have been suggested to be associated with neoplastic progression.

The effect of queuosine on tRNA structure and function

Computational modeling was performed to determine the potential function of the queuosine modification of tRNA found in wobble position 34 of tRNAasp, tRNAasn, tRNAhis, and tRNAtyr. Using the crystal structure of tRNAasp and a tRNA-tRNA-mRNA complex model, we show that the queuosine modification serves as a structurally restrictive base for tRNA anticodon loop flexibility. An extended intraresidue and intramolecular hydrogen bonding network is established by queuosine. The quaternary amine of the 7-aminomethyl side chain hydrogen bonds with the base's carbonyl oxygen. This positions the dihydroxycyclopentenediol ring of queuosine in proper orientation for hydrogen bonding with the backbone of the neighboring uridine 33 residue. The interresidue association stabilizes the formation of a cross-loop hydrogen bond between the uridine 33 base and the phosphoribosyl backbone of the cytosine at position 36. Additional interactions between RNAs in the translation complex were studied with regard to potential codon context and codon bias effects. Neither steric nor electrostatic interaction occurs between aminoacyl- and peptidyl-site tRNA anticodon loops that are modified with queuosine. However, there is a difference in the strength of anticodon/codon associations (codon bias) based on the presence or lack of queuosine in the wobble position of the tRNA. Unmodified (guanosine-containing) tRNAasp forms a very stable association with cytosine (GAC), but is much less stable in complex with a uridine-containing codon (GAU). Queuosine-modified tRNAasp exhibits no bias for either of cognate codons GAC or GAU and demonstrates a lower binding energy similar to the wobble pairing of guanosine-containing tRNA with a GAU codon. This is proposed to be due to the inflexibility of the queuosine-modified anticodon loop to accommodate proper positioning for optimal Watson-Crick type associations. A preliminary survey of codon usage patterns in oncodevelopmental versus housekeeping gene transcripts suggests a significant difference in bias for the queuosine-associated codons. Therefore, the queuosine modification may have the potential to influence cellular growth and differentiation by codon bias-based regulation of protein synthesis for discrete mRNA transcripts.

Modulation of queuine uptake and incorporation into tRNA by protein kinase C and protein phosphatase

It has been suggested that the rate of queuine uptake into cultured human fibroblasts is controlled by phosphorylation levels within the cell. We show that the uptake of queuine is stimulated by activators of protein kinase C (PKC) and inhibitors of protein phosphatase; while inhibitors of PKC, and down-regulation of PKC by chronic exposure to phorbol esters inhibit the uptake of queuine into cultured human fibroblasts. Activators of cAMP- and cGMP-dependent kinases exert no effect on the uptake of queuine into fibroblast cell cultures. These studies suggest that PKC directly supports the activity of the queuine uptake mechanism, and that protein phosphatase activity in the cell acts to reverse this. Regardless of the modulation of uptake rate, the level of intracellular queuine base saturates in 6 h. However, there is still an effect on the incorporation rate of queuine into tRNA of fibroblast cultures even after 24 h. We now show that the incorporation of queuine into tRNA in cultured human fibroblasts by tRNA-guanine ribosyltransferase (TGRase) is also stimulated by activators of PKC and inhibitors of protein phosphatase; while inhibitors of PKC decrease the activity of this enzyme. These studies suggest that PKC supports both the cellular transport of queuine and the activity of TGRase in cultured human fibroblasts, and that protein phosphatase activity in fibroblasts acts to reverse this phenomenon. A kinase-phosphatase control system, that is common to controlling both intracellular signal transduction and many enzyme systems, appears to be controlling the availability of the queuine substrate and the mechanism for its incorporation into tRNA. Since hypomodification of transfer RNA with queuine is commonly observed in undifferentiated, rapidly growing and neoplastically transformed cells, phosphorylation of the queuine modification system may be a critical regulatory mechanism for the modification of tRNA and subsequent control of cell growth and differentiation.

Activation of transfer RNA-guanine ribosyltransferase by protein kinase C

Transfer RNA-guanine ribosyltransferase (TGRase) irreversibly incorporates queuine into the first position in the anticodon of four tRNA isoacceptors. Rat brain protein kinase C (PKC) was shown to stimulate rat liver TGRase activity. TGRase preparations derived from rat liver have been observed to decrease in activity over time in storage at -20 or -70 degrees C. Contamination of the samples by phosphatases was indicated by a p-nitrophenylphosphate conversion test. The addition of micromolar concentrations of the phosphatase inhibitors sodium pyrophosphate and sodium fluoride into TGRase isolation buffers resulted in a greater return of TGRase activity than without these inhibitors. Inactive TGRase preparations were reactivated to their original activity with the addition of PKC. In assays combining both TGRase and PKC enzymes, inhibitors of protein kinase C (sphingosine, staurosporine, H-7 and calphostin C) all blocked the reactivation of TGRase, whereas activators of protein kinase C (calcium, diacylglycerol and phosphatidyl serine) increased the activity of TGRase. None of the PKC modulators affected TGRase activity directly. Alkaline phosphatase, when added to assays, decreased the activity of TGRase and also blocked the reactivation of TGRase with PKC. Denaturing PAGE and autoradiography was performed on TGRase isolates that had been labelled with 32P by PKC. The resulting strong 60 kDa band (containing the major site for phosphorylation) and weak 34.5 kDa band (containing the TGRase activity) are suggested to associate to make up a 104 kDa heterodimer that comprises the TGRase enzyme. This was corroberated by native and denaturing size-exclusion chromatography. These results suggest that PKC-dependent phosphorylation of TGRase is tied to efficient enzymatic function and therefore control of the queuine modification of tRNA.

Absence of tRNA-guanine transglycosylase in a human colon adenocarcinoma cell line

Queuosine (Q), found exclusively in the first position of the anticodons of tRNA(Asp), tRNA(Asn), tRNA(His) and tRNA(Tyr), is synthesized in eucaryotes by a base-for-base exchange of queuine, the base of Q, for guanine at tRNA position 34. This reaction is catalyzed by the enzyme tRNA-guanine transglycosylase (EC 2.4.2.29). We measured the specific release of queuine from Q-5'-phosphate (queuine salvage) and the extent of tRNA Q modification in 6 human tumors carried as xenografts in immune-deprived mice. Q-deficient tRNA was found in 3 of the tumors but it did not correlate with diminished queuine salvage. The low tRNA Q content of one tumor, the HxGC3 colon adenocarcinoma, prompted us to examine a HxGC3-derived cell line, GC3/M. GC3/M completely lacks Q in its tRNA and measurable tRNA-guanine transglycosylase activity; the first example of a higher eucaryotic cell which lacks this enzyme. Exposure of GC3/M cells to 5-azacytidine induces the transient appearance of Q-positive tRNA. This result suggests that at least one allele of the transglycosylase gene in GC3/M cells may have been inactivated by DNA methylation. In clinical samples, we found Q-deficient tRNA in 10 of 46 solid tumors, including 2 of 13 colonic carcinomas.

Protein kinase C modulation of queuine uptake in cultured human fibroblasts

Protein kinase C modulates the activity of a highly specific uptake mechanism for queuine in cultured human fibroblasts. Activators of protein kinase C induce an increased uptake rate for the radiolabeled analog of queuine, rQT3. The protein kinase C inhibitors, H-7, staurosporine and sphingosine all induced a dramatic decrease in the uptake rate of rQT3. This suggests that protein kinase C is tied to efficient cellular uptake of queuine. Uptake is prerequisite to the modification of transfer RNA with queuine. Perturbation of queuine-modified transfer RNA levels has been associated with neoplastic transformation, differentiation and growth control.

Interferon induced inhibition of queuine uptake in cultured human fibroblasts

Interferon inhibits uptake of the radiolabeled queuine analog, rQT3, into cultured human fibroblasts. Simultaneous exposure to 10 nM phorbol-12,13-didecanoate (PDD) potentiates interferon-induced inhibition of rQT3 into cultured fibroblasts. All three major classes of human interferon tested affected uptake similarly, with fibroblast derived beta-interferon being more effective in dose response than gamma or alpha interferons. This suggests that endogenous production of interferon by cultured cells, such as that observed during a low grade viral infection, inhibits queuine uptake and may subsequently lead to a decreased level of queuine modified transfer RNA. Queuine-hypomodified transfer RNA has been implicated in growth control, differentiation and neoplastic transformation.

Identifying inhibitors of queuine modification of tRNA in cultured cells

Altered queuine modification of tRNA has been associated with cellular development, differentiation, and neoplastic transformation. Present methods of evaluating agents for their ability to induce queuine hypomodification of tRNA are tedious, time-consuming, and not readily amenable to examining cell-type or tissue specificity. Therefore, a rapid, small-scale assay was developed to identify agents that alter queuine modification of tRNA in cultured cells. Monolayer cultures (2cm2) of Chinese hamster embryo cells depleted of queuine for 24 h were evaluated for their ability to incorporate [3H]dihydroqueuine into acid precipitable material (tRNA) in the presence and absence of potential inhibitors. Known inhibitors of the queuine modification enzyme tRNA-guanine ribosyltransferase (e.g., 7-methylguanine, 6-thio-guanine, and 8-azaguanine) were very effective in blocking incorporation of the radiolabel, and the dose-dependent results exhibited small standard deviations in independent experiments. The data indicate that the method is rapid, reliable, and potentially useful with a variety of cell types.

Inhibition of queuine uptake in diploid human fibroblasts by phorbol-12,13-didecanoate. Requirement for a factor derived from early passage cells

Cell cultures derived from human neonatal foreskins (HF cells) are susceptible to phorbol-12,13-didecanoate- (PDD) induced inhibition of queuine uptake, but this inhibition is pronounced only in early passage HF cells. The present analysis of five different primary cultures demonstrated that, between 10 and 30 population doublings beyond the primary cultures, HF cells gradually became refractile to PDD-induced inhibition of queuine uptake, after which PDD begins to stimulate queuine uptake. Treating late passage HF cells with conditioned medium from early passage HF cells partially restored the PDD-induced inhibition of queuine uptake. This indicates the existence of a factor produced by early passage HF cells that permits PDD to inhibit queuine uptake. The tumor promoter, teleocidin, mimics the effects of PDD on queuine uptake. Both PDD and teleocidin are known to activate protein kinase C; therefore, this kinase may be an intermediary in tumor promoter-induced effects on queuine uptake. Epidermal growth factor, platelet-derived growth factor, and transforming growth factor beta stimulated queuine uptake in both early and late passage HF cells. Growth factor stimulation of uptake was enhanced by PDD in late passage cells but inhibited by PDD in early passage cells. Polyinosinic polycytidylic acid treatment of late passage HF cells partially restored PDD-induced inhibition of queuine uptake. Human recombinant beta-interferon, plus or minus PDD, had no effect on queuine uptake. PDD did not inhibit queuine uptake in the immortal human and non-human cell lines examined.

Inhibition of queuine uptake in cultured human fibroblasts by phorbol-12,13-didecanoate

The modified base queuine is inserted posttranscriptionally into the first position of the anticodon of tyrosine tRNA, histidine tRNA, asparginine tRNA, and aspartic acid tRNA. Phorbol-12,13-didecanoate (PDD) effects a decrease in the queuine content of tRNA in cultured human foreskin fibroblasts. The present data suggest that this results from a PDD-mediated inhibition of queuine uptake. Nonsaturable uptake was observed for tritiated dihydroqueuine (rQT3) for up to 2 hr at 10 to 1000 nM concentrations, while saturation of uptake was observed after 3 to 4 hr. Lineweaver-Burke analysis of concentration versus uptake revealed biphasic uptake kinetics with high and low Km components of approximately 350 and 30 nM, respectively. Competition by queuine of rQT3 uptake indicated that both compounds have equal affinity for the uptake mechanism. PDD inhibited rQT3 uptake but required 30 to 60 min of exposure before the uptake was completely blocked. The rQT3 efflux rate from cells was found to be 3 to 4 times greater than that of uptake, and PDD also inhibited the efflux reaction. The potential inhibitors furosemide, nitrobenzylthioinosine, ouabain, 7-methylguanine, 7-deazaguanine, guanine, guanosine, adenine, adenosine, hypoxanthine, and epidermal growth factor had no effect on rQT3 uptake. However, dipyridamole was immediately effective at reducing rQT3 uptake.

Relationship between a tumor promoter-induced decrease in queuine modification of transfer RNA in normal human cells and the expression of an altered cell phenotype

With normal human skin fibroblasts in culture, a transient decrease in queuine modification of tRNA precedes a phorbol ester tumor promoter-induced 5- to 10-fold increase in saturation density. Subsequently, an increase in the queuine content of cellular tRNA (to levels comparable to those in untreated cultures) precedes a decrease in saturation density. This reversal of the phorbol ester-induced alteration in tRNA modification occurs in the continued presence of the tumor promoter, and it parallels an increased ability of the cells to salvage queuine from catabolized endogenous tRNA. Addition of exogenous queuine concurrently with the tumor promoter at early passage significantly inhibits the increase in saturation density. The results suggest a role for the decrease in queuine modification of tRNA in mediating the phenotypic change induced by the tumor promoter.

Inosine biosynthesis in transfer RNA by an enzymatic insertion of hypoxanthine

An enzyme was discovered which incorporates hypoxanthine into mature tRNA macromolecules. This enzyme is postulated to be similar to tRNA-guanine ribosyltransferase which inserts 7-(3,4-trans-4,5-cis-dihydroxy-1-cyclopenten-3-ylaminomethyl )-7-deazaguanine into the first position of the anticodon of four tRNAs. The hypoxanthine-incorporating enzyme has been assayed in extracts of rat liver and cultured human leukemia cells and it has been resolved from tRNA-guanine ribosyltransferase by DEAE-cellulose column chromatography. The enzyme assay is based on the incorporation of radiolabeled hypoxanthine into unfractionated heterologous tRNA and the reaction rate is proportional to the amount of added enzyme extract. Hydrolysis of the radiolabeled tRNA and analysis of the nucleoside composition yields inosine (the nucleoside of hypoxanthine) as the only radiolabeled product. It is proposed that the enzyme, a tRNA-hypoxanthine ribosyltransferase, is responsible for the biosynthesis of inosine in the anticodon wobble position of specific tRNAs, resulting in greatly expanded codon recognition by these tRNAs.

Interaction of 2-aminobicyclo[3.2.1]octane-2-carboxylic acid with the amino acid transport systems of the sarcoma 37 murine ascites tumor cell

The relatively broad and overlapping specificities of amino acid transport systems have made the synthesis of analogues specific to single transport systems desirable. The analogue in general use as a specific substrate for transport system L has been 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH). The affinity of BCH for the binding site of system L has been shown to be less than that of the natural substrate, leucine. Earlier studies from this laboratory suggested that higher homologues in a series could have greater affinity for system L. A higher homologue of BCH, 2-aminobicyclo[3.2.1]octane-2-carboxylic acid (ABOCA), has been synthesized and studied as a substrate and competitor for amino acid transport systems of the sarcoma 37 (S37) ascites cell. ABOCA inhibited the transport system dominant in the low concentration region for histidine uptake (system L) but had no effect on the uptake of labeled N-methyl-alpha-aminoisobutyric acid (MeAIB). MeAIB had no effect on labeled ABOCA uptake in S37 cells. ABOCA inhibited the uptakes of labeled leucine and labeled BCH competitively. Leucine, histidine, and BCH inhibited the uptake of labeled ABOCA competitively. Typical L system substrates demonstrated exchange effects with labeled ABOCA. The b isomer of ABOCA demonstrated slightly greater affinity for system L than did the a isomer. We conclude that ABOCA is an analogue restricted to interaction with amino acid transport system L, that it has greater affinity for system L than does BCH, and that its selection for system l is determined principally by an apolar interaction with steric considerations secondary.