Maveropepimut-S, a DPX-based immune-educating therapy, shows promising and durable clinical benefit in patients with recurrent ovarian cancer, a phase 2 trial

PURPOSE

Patients with platinum resistant ovarian cancer (OvCa) respond poorly to existing therapies. Hence there is a need for more effective treatments.

METHODS

The DeCidE1 trial is a multicenter, randomized, open-label, single-arm phase 2 study to evaluate the safety and effectiveness of maveropepimut-S (MVP-S) with cyclophosphamide (CPA) in patients with recurrent ovarian cancer. Median follow-up for evaluable subjects was 4.4 months. Data were collected from March 2019 to June 2021. Subjects received two injections of 0.25 mL MVP-S 3 weeks apart, followed by one 0.1 mL doses, every 8 weeks up to progression. Oral CPA, 50 mg twice daily, was administered in repeating weekly on and off cycles.

RESULTS

Twenty-two patients were enrolled. Median age was 58 years (38-78 years). Among the evaluable population, ORR was 21% (90% CI, 7.5%-41.9%), with a DCR of 63% (90% CI, 41.8%-81.3%), including 4 (21%) patients with partial responses, 8 (42%) stable disease, and 7 (37%) progressive disease. The ORRs were consistent across subgroups based on platinum-sensitivity, and DCR was higher in the platinum-resistant subpopulation. Four stable disease patients maintained clinical benefit up to 25 months. Most treatment related adverse events (TRAEs) were grade 1 and 2 (87% of unique events). Most common AEs were injection site reactions. Eight subjects reported grade 3 and no grade 4 AEs. Survivin-specific T cell responses were observed in treated patients with clinical benefit.

CONCLUSIONS

MVP-S with intermittent low-dose CPA is well-tolerated, with clinical benefit for patients with recurrent OvCa. Observed responses are irrespective of the platinum status.

Right middle cerebral artery stroke secondary to ovarian clear cell carcinoma in a 35-year-old: A case report

Thromboembolic events (TEEs) can be classified into two types: venous TEEs (vTEEs), such as pulmonary embolism (PE) and deep vein thrombosis (DVT), and arterial TEEs (ATEs), such as acute myocardial infarction and cerebral infarction. Ovarian cancer has a high incidence of venous thromboembolism, with the clear cell subtype carrying the highest risk. However, the incidence of ATEs, especially cerebral infarction, in patients with ovarian carcinoma, of all subtypes, is much lower. This report is of a rare case of a 35-year-old Asian woman who presented with sudden onset of left hemiplegia and right gaze as the first presenting signs of an underlying ovarian malignancy. The patient had no pertinent medical history and no underlying cardiovascular risk factors. Final diagnosis was stage 2B clear cell carcinoma of the ovary without lymphovascular invasion arising from endometriosis. Patients who suffer from arterial thrombosis without known atherosclerotic risk factors should undergo further evaluations to rule out the possibility of cancer, particularly ovarian carcinoma.

Whole-Genome Sequencing Identifies PPARGC1A as a Putative Modifier of Cancer Risk in BRCA1/2 Mutation Carriers

While BRCA1 and BRCA2 mutations are known to confer the largest risk of breast cancer and ovarian cancer, the incomplete penetrance of the mutations and the substantial variability in age at cancer onset among carriers suggest additional factors modifying the risk of cancer in BRCA1/2 mutation carriers. To identify genetic modifiers of BRCA1/2, we carried out a whole-genome sequencing study of 66 ovarian cancer patients that were enriched with BRCA carriers, followed by validation using data from the Pan-Cancer Analysis of Whole Genomes Consortium. We found PPARGC1A, a master regulator of mitochondrial biogenesis and function, to be highly mutated in BRCA carriers, and patients with both PPARGC1A and BRCA1/2 mutations were diagnosed with breast or ovarian cancer at significantly younger ages, while the mutation status of each gene alone did not significantly associate with age of onset. Our study suggests PPARGC1A as a possible BRCA modifier gene. Upon further validation, this finding can help improve cancer risk prediction and provide personalized preventive care for BRCA carriers.

353 Identification of potential response predictors to maveropepimut-S (DPX-Survivac), a novel T cell activating immunotherapy, in patients with advanced recurrent ovarian cancer

Background

Epithelial ovarian cancer (OvCa) is the most lethal of gynecological malignancies. The high mortality is related to a late diagnosis with over 75% being at an advanced stage, high recurrence rates, and ultimately resistance to chemotherapy. Previous studies have consistently demonstrated a strong association between higher tumor T cell infiltration and improved survival in OvCa patients supporting the potential clinical utility of T cell activating immunotherapy approaches. Maveropepimut-S (MVP-S, formerly named DPX-Survivac) is a T cell activating immunotherapy which is a formulation of the proprietary drug delivery platform DPX™ with immunogenic T-cell epitopes derived from the tumor-associated antigen survivin. MVP-S in combination with intermittent low-dose cyclophosphamide has been shown to induce robust and durable antigen-specific T cell responses and anti-tumor clinical activity in recurrent OvCa patients. The current study presents translational data aimed at identifying tumor tissue-based predictive biomarkers for response to treatment with MVP-S.

Methods

Baseline and on-treatment tumor biopsies were collected from patients treated with MVP-S primed with immune-modulating low dose cyclophosphamide. Multiplex-immunohistochemistry (mIHC, Akoya Biosciences) and RNAseq analyses (Personalis Inc.) were used to analyze the tumor immune environment and identify potential response predictors to MVP-S.

Results

Twenty-two patients with advanced, recurrent OvCa were enrolled in this study. mIHC analysis demonstrated that higher baseline CD3+CD8+ T cell infiltration in tumor tissue was significantly associated with anti-tumor clinical activity of MVP-S defined as >10% on-treatment tumor regression. Pathway enrichment analyses using the differentially expressed genes associated with anti-tumor clinical activity confirmed these findings. In addition, we identified B cell pathway genes to be significantly upregulated in patients with >10% on-treatment tumor regression. mIHC analyses of paired biopsies available for one subject with clinical response (PR) demonstrated that MVP-S treatment induced increased T and B cell infiltration in the on-treatment biopsy compared to the baseline biopsy. These findings suggest that immunogenic tumors are more susceptible to the MVP-S treatment, in line with its mechanism of action. Pathway enrichment analyses further revealed that upregulation of genes or pathways related to immune-suppression (e.g. WNT pathway) or immune evasion/exclusion (CD276, Arg2) were significantly associated with lack of anti-tumor activity indicative of potential mechanism of primary resistance.

Conclusions

Collectively, these results provide insight for possible response predictors to MVP-S based therapy

Trial Registration

NCT02785250

Ethics Approval

The protocol and patient-informed consent form received approval by Institutional Review Boards. Written informed consent was obtained from all patients. REBs: Comite d’ethique de la recherche du CHUM (Montreal, Canada); Western Institutional Review Board 20161075 (Augusta, GA, USA); FWA #00002505 (NEW YORK, NY, USA); FWA00000161, IRB00000471 (Portland, Oregon, USA); University Health Network REB (Toronto, Canada); FWA00000935, FWA00000934 (Standford, CA, USA); Health Research Ethics Board of Alberta, (Edmonton, Canada)

Radiotherapy dose escalation on pelvic lymph node control in patients with cervical cancer

OBJECTIVE

Data supporting dose escalation for node-positive cervical cancer are currently limited to small retrospective studies. The goal of this study was to assess whether radiation dose was associated with lymph node control or gastrointestinal toxicity in patients with node-positive cervical cancer.

METHODS

A total of 390 patients with carcinoma of the uterine cervix were treated between October 1997 and October 2017. Patients included in our analysis were those with squamous cell carcinoma or adenocarcinoma who were node-positive, treated definitively, and with at least one follow-up visit and post-treatment imaging scan. We excluded those without follow-up and those treated with palliative intent. All patients were treated with external beam radiation to pelvic±para-aortic fields with concurrent weekly cisplatin. All lymph nodes present at the time of treatment were stratified by size as <2 cm or ≥2 cm. Acute and late gastrointestinal toxicity were recorded for all patients.

RESULTS

A total of 77 patients with 206 lymph nodes were identified. Median stage at presentation was FIGO IIB. Thirteen patients underwent definitive surgical resection followed by adjuvant radiation, of which 12 were treated to doses ≤5040 (range 2700-5940) cGy. Sixty-four patients were treated with definitive chemoradiation, of which 42 (66%) received ≤5040 (range 4500-5040) cGy and 22 (34%) received >5040 (range 5300-6640) cGy. Patients with pre-chemoradiation lymph nodes ≥2 cm had inferior lymph node control compared with patients with pre-chemoradiation lymph node <2 cm at 12 months (77% vs 100%, p=0.002). Radiation dose >5040 cGy was not significantly associated with improved lymph node control compared with ≤5040 cGy when analyzing all patients (12 months, 100% vs 89%, p=0.112). In patients with pre-chemoradiation lymph nodes ≥2 cm, radiation dose >5040 cGy was associated with improved lymph node control (12 months, 100% vs 60%, p=0.020). Acute grade ≥2 gastrointestinal toxicity was not associated with radiation dose >5040 cGy (20% vs 13%, p=0.424). Two patients developed grade ≥2 late gastrointestinal toxicity, both of whom were treated to ≤5040 cGy.

CONCLUSIONS

This series supports the role of dose escalation for patients with lymph nodes ≥2 cm. Dose escalation is associated with improved control in patients with larger lymph nodes, and is not associated with greater gastrointestinal toxicity.

Whole-exome sequencing of ovarian cancer families uncovers putative predisposition genes

Despite the identification of several ovarian cancer (OC) predisposition genes, a large proportion of familial OC risk remains unexplained. We adopted a two-stage design to identify new OC predisposition genes. We first carried out a large germline whole-exome sequencing study on 158 patients from 140 families with significant OC history, but without evidence of genetic predisposition due to BRCA1/2. We then evaluated the potential candidate genes in a large case-control association study involving 381 OC cases in the Cancer Genome Atlas project and 27,173 population controls from the Exome Aggregation Consortium. Two new putative OC risk genes were identified, namely, ANKRD11, a putative tumor suppressor, and POLE, an enzyme involved in DNA repair and replication. These two genes likely confer moderate OC risk. We performed in vitro experiments and showed an ANKRD11 mutation identified in our patients markedly lowered the protein expression by compromising protein stability. Upon future validation and functional characterization, these genes may shed light on cancer etiology along with improving ascertainment power and preventive care of individuals at high risk of OC.

Management options for a patient with squamous cell carcinoma arising in a mature cystic teratoma of the ovary

Mature cystic teratomas, also referred to as dermoid cysts, are one of the commonly occurring ovarian germ cell tumors. Malignant transformation of a germ cell tumor occurs approximately 1-2% of the time. Treatment options vary by stage and are not well outlined in the literature. Here we report a case of a perimenopausal female who presented with increasing abdominal girth and an elevated CA-125. Final pathology revealed an invasive squamous cell carcinoma, moderately to poorly differentiated, multifocal, arising in a cyst on the left ovary, possibly a teratoma. At the time of diagnosis, the patient was FIGO stage IA. The decision was made against adjuvant treatment. Squamous cell carcinoma arising in a mature cystic teratoma of the ovary is rare. Treatment options are not well outlined in the literature, especially for disease less than stage II. Further research is needed to better inform the clinician on management recommendations.

Effects of 1-methyltryptophan stereoisomers on IDO2 enzyme activity and IDO2-mediated arrest of human T cell proliferation

IDO2 is a newly discovered enzyme with 43 % similarity to classical IDO (IDO1) protein and shares the same critical catalytic residues. IDO1 catalyzes the initial and rate-limiting step in the degradation of tryptophan and is a key enzyme in mediating tumor immune tolerance via arrest of T cell proliferation. The role of IDO2 in human T cell immunity remains controversial. Here, we demonstrate that similar to IDO1, IDO2 also degrades tryptophan into kynurenine and is inhibited more efficiently by Levo-1-methyl tryptophan (L-1MT), an IDO1 competitive inhibitor, than by dextro-methyl tryptophan (D-1MT). Although IDO2 enzyme activity is weaker than IDO1, it is less sensitive to 1-MT inhibition than IDO1. Moreover, our results indicate that human CD4(+) and CD8(+) T cell proliferation was inhibited by IDO2, but both L-1MT and D-1MT could not reverse IDO2-mediated arrest of cell proliferation, even at high concentrations. These data indicate that IDO2 is an inhibitory mechanism in human T cell proliferation and support efforts to develop more effective IDO1 and IDO2 inhibitors in order to overcome IDO-mediated immune tolerance.

Expression and serum immunoreactivity of developmentally restricted differentiation antigens in epithelial ovarian cancer

Cancer-embryo antigens or developmentally restricted differentiation antigens (DRDAGs), such as PLAC1 (CT92) and developmental pluripotency associated-2 (DPPA2/CT100), are expressed in pluripotent embryonic cells. They are also recognized as cancer-testis antigens (CT) which are proteins normally expressed only in the human germ line but that are also present in a significant subset of malignant tumors. These antigens may prove to be markers of 'repopulating' cells with stem cell-like characteristics and could be critical targets for immunotherapy in epithelial ovarian cancer (EOC). Our objective was to define the frequency of expression and immunogenicity of PLAC1 and DPPA2 in EOC and correlate expression with clinical outcome. One-step reverse transcriptase PCR was performed on 101 EOC samples and a panel of normal tissues. Expression of PLAC1 and DPPA2 in the EOC specimens was 21/101 (21%) and 31/101 (31%) respectively. In normal tissues, PLAC1 expression was restricted to the placenta while DPPA2 expression was restricted to the placenta and testis. Immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA) were also performed on a subset of specimens. Humoral immunity was demonstrable in 2/12 serum samples from patients whose tumors expressed DPPA2. There was no demonstrable antibody response to PLAC1 in patients with PLAC1 positive tumors. The presence of PLAC1 and DPPA2 did not have a statistically significant effect on recurrence-free and overall survival. The tissue-restricted expression of PLAC1 and DPPA2, their expression in a significant proportion of EOC patients, and their potential to represent markers of stem cells make DRDAGs attractive targets for antigen-specific immunotherapy in EOC.

Efficacy of levo-1-methyl tryptophan and dextro-1-methyl tryptophan in reversing indoleamine-2,3-dioxygenase-mediated arrest of T-cell proliferation in human epithelial ovarian cancer

It has been reported that levo-1-methyl tryptophan (L-1MT) can block indoleamine-2,3-dioxygenase (IDO) expressed by human dendritic cells (DC), whereas dextro-1-methyl tryptophan (D-1MT) is inefficient. However, whether L-1MT or D-1MT can efficiently reverse IDO-induced arrest of human T-cell proliferation has not been clarified. Here, we show a marked immunosuppressive effect of IDO derived from INDO-transfected 293 cell, IDO+ ovarian cancer cells, and monocyte-derived DCs on CD4+ Th1 cells, CD8+ T cells, and natural killer cells derived from peripheral blood, ascites, and tumors of ovarian cancer patients. We found that, whereas L-1MT and D/L-1MT can restore proliferation of tumor-derived and peripheral blood T-cell subsets, D-1MT does not effectively restore IDO-induced arrest of T-cell proliferation. Although D-1MT inhibited kynurenine production at high concentrations, L-1MT was more effective in abrogating kynurenine generation and tryptophan depletion, whereas tryptophan was completely depleted by IDO even in the presence of high amounts of D-1MT. Together, the results indicate that, whereas the generation of tryptophan metabolites (kynurenines) by IDO is important in mediating suppression of T-cell proliferation, the degree to which tryptophan depletion is restored by 1MT is also critical in overcoming IDO-induced arrest of T-cell proliferation.

Vaccination with an NY-ESO-1 peptide of HLA class I/II specificities induces integrated humoral and T cell responses in ovarian cancer

NY-ESO-1 is a "cancer-testis" antigen expressed in epithelial ovarian cancer (EOC) and is among the most immunogenic tumor antigens defined to date. The NY-ESO-1 peptide epitope, ESO(157-170), is recognized by HLA-DP4-restricted CD4+ T cells and HLA-A2- and A24-restricted CD8+ T cells. To test whether providing cognate helper CD4+ T cells would enhance the antitumor immune response, we conducted a phase I clinical trial of immunization with ESO(157-170) mixed with incomplete Freund's adjuvant (Montanide ISA51) in 18 HLA-DP4+ EOC patients with minimal disease burden. NY-ESO-1-specific Ab responses and/or specific HLA-A2-restricted CD8+ and HLA-DP4-restricted CD4+ T cell responses were induced by a course of at least five vaccinations at three weekly intervals in a high proportion of patients. There were no serious vaccine-related adverse events. Vaccine-induced CD8+ and CD4+ T cell clones were shown to recognize NY-ESO-1-expressing tumor targets. T cell receptor analysis indicated that tumor-recognizing CD4+ T cell clones were structurally distinct from non-tumor-recognizing clones. Long-lived and functional vaccine-elicited CD8+ and CD4+ T cells were detectable in some patients up to 12 months after immunization. These results confirm the paradigm that the provision of cognate CD4+ T cell help is important for cancer vaccine design and provides the rationale for a phase II study design using ESO(157-170) epitope or the full-length NY-ESO-1 protein for immunotherapy in patients with EOC.

Clinical and pathological predictive factors in women with adult-type granulosa cell tumor of the ovary

Granulosa cell tumor (GCT) is a rare neoplasm hallmarked by a very indolent course and late recurrences. Although numerous clinical and pathological parameters have been implicated as prognostic factors for GCT, their role remains controversial. We performed a retrospective study at our institution where we identified 48 patients with GCT from our tumor registry. Demographic and clinical course information was recorded from the medical record. Twenty of 48 formalin-fixed, paraffin-embedded blocks were retrieved from archived specimens. Pathological parameters such as nuclear atypia, mitotic count, Ki-67 index using immunohistochemistry, and quantitative DNA ploidy were performed. DNA aneuploidy by quantitative method was associated with patients' overall survival. The degree of nuclear atypia, mitotic count, Ki-67 index, and DNA aneuploidy was not predictive of tumor recurrence. Multi-institutional collaboration is imperative to create a comprehensive national database for investigation into ways that may better indicate prognosis in these patients.

Optimising Treatment of Elderly Patients with Ovarian Cancer

The aging population is the fastest growing segment of our population. Over the last century, the average life expectancy has increased by 25 years. The incidence of ovarian carcinoma, seen primarily in postmenopausal women, is, therefore, expected to increase. The current standard treatment of ovarian cancer has been determined on the basis of prospective, randomised clinical trials carried out by cooperative groups. Sixty-one percent of new cancer cases occur in women >65 years of age. Despite this fact, enrollment in clinical trials has been exceedingly low. In turn, this causes suboptimal treatment for a very fatal disease. The aetiology of this is multifactorial, and strategies for improvement are lacking. Elderly patients may be barred from participation based on physician biases alone. Elderly patients may have limited access to academic centres where clinical trials are conducted or be excluded on the basis of unrealistic inclusion criteria. As physicians, it is our duty to understand the elderly patient and the comorbidities in this age group that may influence the tolerability and toxicity of conventional therapies. Therefore, it is imperative that we make a conscious effort to examine ways in which we may improve enrollment of elderly women with ovarian cancer in clinical trials.

Response of combination platinum and gemcitabine chemotherapy for recurrent epithelial ovarian carcinoma

OBJECTIVE

It has been postulated that gemcitabine inhibits DNA repair, and platinum resistance is due to increased DNA repair activity. The addition of gemcitabine to platinum-based agents may have synergistic tumoricidal activity.

METHODS

Retrospective chart review of all patients with recurrent, persistent, or progressive fallopian tube or ovarian carcinoma treated with a platinum-based compound and gemcitabine from 2001 to present was performed.

RESULTS

Twenty-nine patients on second to eight line chemotherapy met inclusion criteria. The median age was 53 years. Twenty-two patients received cisplatin and gemcitabine, and 7 patients received carboplatin and gemcitabine based on results of chemoresistance assays or prior chemorelated toxicities. The intent to treat was with six cycles of gemcitabine (1000 mg/m(2)) and either cisplatin (75 mg/m(2)) or carboplatin (AUC 5) day 1 and gemcitabine only on day 8 of a 21-day cycle. The median number of cycles administered was six. There were 20 grade 3 and 4 toxicities and 63% of patients by cycle 6 needed erythropoietin marrow support and 19% needed GCSF support by cycle 4. Twenty-one patients required discontinuation of day 8 that most commonly occurred at cycle 4. Eleven (38%) had CR, 5 (17%) had PR, 6 (21%) had SD, and 7 (24%) had PD, which is a 55% overall response. Nineteen of 29 patients (66%) showed platinum resistance to initial therapy. Of those, four (21%) had CR, four (21%) had PR, six (32%) had SD, and five (26%) with PD, which demonstrates a 42% overall response rate for this particular subset of patients.

CONCLUSIONS

Adjuvant combination platinum-based agent with gemcitabine is a very effective and well-tolerated treatment for recurrent fallopian tube or ovarian carcinoma; even in those who exhibit initial platinum resistance.

Promoter hypermethylation of FANCF: disruption of Fanconi Anemia-BRCA pathway in cervical cancer

Patients with advanced stage invasive cervical cancer (CC) exhibit highly complex genomic alterations and respond poorly to conventional treatment protocols. In our efforts to understand the molecular genetic basis of CC, we examined the role of Fanconi Anemia (FA)-BRCA pathway. Here, we show that FANCF gene is disrupted by either promoter hypermethylation and/or deregulated gene expression in a majority of CC. Inhibition of DNA methylation and histone deacetylases induces FANCF gene re-expression in CC cell lines. FANCF-deregulated CC cell lines also exhibit a chromosomal hypersensitivity phenotype after exposure to an alkylating agent, a characteristic of FA patients. We also show the involvement of BRCA1 gene by promoter hypermethylation or down-regulated expression in a small subset of CC patients. Thus, we have found inactivation of genes in the FA-BRCA pathway by epigenetic alterations in a high proportion of CC patients, suggesting a major role for this pathway in the development of cervical cancer. Thus, these results have important implications in understanding the molecular basis of CC tumorigenesis and clinical management in designing targeted experimental therapeutic protocols.

Frequent promoter methylation of CDH1, DAPK, RARB, and HIC1 genes in carcinoma of cervix uteri: its relationship to clinical outcome

BACKGROUND

Cervical cancer (CC), a leading cause of cancer-related deaths in women worldwide, has been causally linked to genital human papillomavirus (HPV) infection. Although a host of genetic alterations have been identified, molecular basis of CC development is still poorly understood.

RESULTS

We examined the role of promoter hypermethylation, an epigenetic alteration that is associated with the silencing tumor suppressor genes in human cancer, by studying 16 gene promoters in 90 CC cases. We found a high frequency of promoter methylation in CDH1, DAPK, RARB, and HIC1 genes. Correlation of promoter methylation with clinical characteristics and other genetic changes revealed the following: a) overall promoter methylation was higher in more advanced stage of the disease, b) promoter methylation of RARB and BRCA1 predicted worse prognosis, and c) the HIC1 promoter methylation was frequently seen in association with microsatellite instability. Promoter methylation was associated with gene silencing in CC cell lines. Treatment with methylation or histone deacetylation-inhibiting agents resulted in profound reactivation of gene expression.

CONCLUSIONS

These results may have implications in understanding the underlying epigenetic mechanisms in CC development, provide prognostic indicators, and identify important gene targets for treatment.

Postpartum angiographic embolization for vulvovaginal hematoma. A report of two cases

BACKGROUND

Puerperal hematomas can become a life-threatening obstetric emergency. Their incidence is 1 or 2/1,000 deliveries. When mainstay methods of suture and packing fail, arterial embolization becomes an excellent alternative to definitive treatment, laparotomy.

CASES

A 32-year-old woman, para 2-0-2-2, developed extreme rectal and vulvar pain one hour postpartum. A 12 x 10-cm vulvovaginal hematoma was identified, drained, sutured and packed. Bleeding continued, blood products were administered, and selective angiographic embolization of the pudendal and inferior gluteal arteries was successfully performed. A 31-year-old woman, para 1-0-1-1, developed a left vaginal hematoma immediately postpartum. She failed vaginal packing and underwent angiographic arterial embolization successfully. The patient was discharged on the fourth postpartum day. At six weeks postpartum, neither patient had evidence of hematoma formation.

CONCLUSION

In the setting of a puerperal hematoma refractory to conventional first-line therapy, arterial embolization provides a rational, effective alternative for achieving hemostasis with minimal morbidity.

Chemical and biological profiles of sediments as indicators of sources of genotoxic contamination in Hamilton Harbour. Part I: analysis of polycyclic aromatic hydrocarbons and thia-arene compounds

Bottom sediment and suspended sediment samples from Hamilton Harbour (western Lake Ontario) and from a major tributary were profiled using polycyclic aromatic hydrocarbons (PAH) and thia-arenes as source apportionment tracers. Ratios of selected PAH and ratios of monomethyl and dimethyl/ethyl dibenzothiophenes to the parent dibenzothiophenes were calculated. Thia-arene and PAH profiles of Standard Reference Material SRM 1649 (urban dust/organics), SRM 1650 (diesel), SRM 1597 (coal tar), Hamilton coal tar and a composite Hamilton air particulate sample provided source sample data. The gas chromatography-mass spectrometry (GC-MS) chromatograms of all sample extracts were dominated by homocyclic PAH but interpretation of PAH profiles with respect to source was difficult. In contrast, thia-arene analyses revealed more distinct differences in profiles of samples collected in different areas of the harbour, including the tributary. These results indicated that areas of coal tar-contaminated sediment are potential contributors to the overall contaminant burden of sediments and suspended sediments in Hamilton Harbour. These data also indicated that contaminants related to mobile combustion sources were entering the harbour via a major tributary.

Chemical and biological profiles of sediments as indicators of sources of contamination in Hamilton Harbour. Part II: bioassay-directed fractionation using the Ames Salmonella/microsome assay

Bottom sediment and suspended sediment samples from Hamilton Harbour (western Lake Ontario) and from a major tributary were profiled using a bioassay-directed fractionation approach. Sample extracts were fractionated using an alumina/Sephadex gel clean-up procedure to afford non-polar aromatic fractions which were characterized using chemical analyses and the Ames/microsome bacterial assay in Salmonella typhimurium strains YG1025 with the addition of oxidative metabolism (S9), and YG1024 without S9. Non-polar aromatic fractions of selected samples were separated by normal phase HPLC into 1-min fractions which were subjected to bioassay analyses. The bioassays using strain YG1025+S9, a TA100-type strain, were performed to assess genotoxicity arising from the presence of polycyclic aromatic hydrocarbons (PAH). Fractions which exhibited mutagenic activity contained PAH with molecular masses of 252, 276 and 278 amu; these fractions contained over 80% of the genotoxicity attributable to PAH. Individual compounds identified using Gas Chromatography-Mass Spectrometry analyses in these active fractions included benzo[a]pyrene, indeno[cd]pyrene and dibenz[a,h]anthracene. The YG1025+S9 mutagenic activity profiles were similar for all samples. Mutagenic activity profiles generated using strain YG1024-S9, a TA98-type strain sensitive to compounds characteristic of mobile source emissions, were very different. The mutagenic activities in strain YG1024-S9 were greatest for harbour-suspended sediment samples collected from sites impacted by a major tributary. Suspended sediments collected near areas known to contain high levels of coal tar-contamination in the bottom sediments contained higher levels of genotoxic PAH than suspended sediments collected from other areas of the harbour.