Metastatic primary breast neuroendocrine neoplasms: a case series.

BACKGROUND: Breast neuroendocrine neoplasms represent a rare subtype of breast cancer which have not been well studied or characterised, particularly in the metastatic setting. AIM: To present clinicopathological characteristics, treatment and outcomes of a series of patients with metastatic neuroendocrine carcinoma of the breast and review the current literature. METHODS: We performed a retrospective review to identify and describe patients with metastatic neuroendocrine carcinoma of the breast at our centre between 2011 and 2021. Medical records, pathology and imaging results were examined to evaluate the clinical and histopathological features as well as the treatment pathways and prognosis of these patients. RESULTS: We present a series of seven female patients with metastatic neuroendocrine carcinoma of the breast, as defined by the World Health Organization classification, over a period of 10 years (2011-2021) from a single centre. Median age at diagnosis was 48 years (range 39-63). Six of seven tissue samples expressed synaptophysin and chromogranin and were also oestrogen and progesterone receptor positive; median Ki-67 index was 50% (range 20-90%). All seven patients had demonstrated avidity on 18 F-FDG PET imaging, and the six who underwent 68 Ga-DOTATATE PET all had significant avidity. Treatment modalities and sequencing varied, but all patients received chemotherapy during their disease course. Six patients received three or more lines of treatment. Median overall survival was 31.8 months (range 3.7-108.6). Median progression-free survival (PFS) with first-line therapy for metastatic disease was 5.8 months (range 1.8-37.8). CONCLUSIONS: This series shows the use of multiple modalities in treating this disease, with different sequencing in different patients. Despite multiple modalities used in the first-line setting, first-line PFS remains short. Larger series and further molecular characterisation are required to aid clinicians in managing this condition and to guide optimal treatment sequencing to improve outcomes in this rare patient group.

Australasian Consensus Statement on the Identification, Prevention, and Management of Hormonal Crises in Patients with Neuroendocrine Neoplasms Undergoing Peptide Receptor Radionuclide Therapy.

Hormonal crises are a rare but increasingly recognized phenomenon following peptide receptor radionuclide therapy (PRRT) in patients with neuroendocrine neoplasms (NENs). Due to the paucity of published studies, approaches to the identification, prevention, and management of risk factors are inconsistent between different institutions. This consensus statement aimed to provide guidance for NEN patients undergoing PRRT. Our statement has been created on the basis of clinical demand and concerns regarding the precipitation of hormonal crises. A formal literature review was conducted to identify available studies. A total of 19 Australian and New Zealand experts in the fields of medical oncology, nuclear medicine, anaesthetics, and endocrinology collaborated on this consensus statement. The main focus is on carcinoid crises. Other hormonal crises seen in patients with functional pancreatic NENs are addressed briefly. These recommendations are relevant to PRRT centres internationally and should be tailored to local experience and available resources.

Overall survival with circulating tumor DNA-guided therapy in advanced non-small-cell lung cancer.

Circulating tumor DNA (ctDNA) sequencing guides therapy decisions but has been studied mostly in small cohorts without sufficient follow-up to determine its influence on overall survival. We prospectively followed an international cohort of 1,127 patients with non-small-cell lung cancer and ctDNA-guided therapy. ctDNA detection was associated with shorter survival (hazard ratio (HR), 2.05; 95% confidence interval (CI), 1.74-2.42; P < 0.001) independently of clinicopathologic features and metabolic tumor volume. Among the 722 (64%) patients with detectable ctDNA, 255 (23%) matched to targeted therapy by ctDNA sequencing had longer survival than those not treated with targeted therapy (HR, 0.63; 95% CI, 0.52-0.76; P < 0.001). Genomic alterations in ctDNA not detected by time-matched tissue sequencing were found in 25% of the patients. These ctDNA-only alterations disproportionately featured subclonal drivers of resistance, including RICTOR and PIK3CA alterations, and were associated with short survival. Minimally invasive ctDNA profiling can identify heterogeneous drivers not captured in tissue sequencing and expand community access to life-prolonging therapy.

Synchronous Operable Pancreatic and Breast Cancer Without Genetic Mutation: A Literature Review and Discussion.

Background: Synchronous cancers are rarely detected when working-up a patient for a primary cancer. Neoadjuvant management of synchronous breast and pancreatic cancers, without a germline mutation, has yet to be discussed. Two patients were diagnosed with synchronous breast and pancreatic cancers at our institution over the last decade. A literature review was performed to evaluate the current evidence stance. Results: The first patient was 61-years old and diagnosed with a HER2+ breast cancer. The second patient was 77-years old and diagnosed with a Luminal B breast cancer. The inability to provide concurrent breast and pancreatic neoadjuvant therapy for the HER2+ patient, resulted in upfront surgery. The second patient was able to have both cancers treated simultaneously - neoadjuvant chemotherapy to the pancreas, and neoadjuvant endocrine therapy to the breast. Discuss: There is no single neoadjuvant regimen that treats both pancreatic and breast cancer. The differences in breast cancer sub-types impacted our neoadjuvant options. Our recent experience led us to the hypothesis that breast cancer care dictates treatment, while pancreatic cancer determines survival. There is a significant paucity in the literature regarding synchronous breast and pancreatic cancer.

Differential effects of radiation fractionation regimens on glioblastoma.

BACKGROUND: Radiotherapy (RT) is a mainstay of treatment for patients with glioblastoma (GB). Early clinical trials show that short course hypofractionation showed no survival benefit compared to conventional regimens with or without temozolomide chemotherapy (TMZ) but reduces the number of doses required. Concerns around delayed neurological deficits and reduced cognition from short course hypofractionated RT remain a concern. The aim of this study was to evaluate the effect of increased interfractional time using two different radiation fractionation regimens on GB. METHODS: The radiobiological effect of increasing doses 0-20 Gy x-ray photon RT on Gl261 and CT2A GB cell lines was compared by colony forming assay, DNA damage by alkaline comet assay, oxidative stress, DNA damage, cell cycle, and caspase-3/7 by MUSE® flow cytometric analyses, and protein expression by western blot analyses. Conventional (20 Gy/10 fractions) and hypofractionated (20 Gy/4 fractions spaced 72 h apart) RT regimens with and without TMZ (200 mg/kg/day) were performed in syngeneic Gl261 and CT2A intracranial mouse models using the Small Animal Radiation Research Platform (Xstrahl Inc.). RESULTS: X-ray photon radiation dose-dependently increased reactive oxygen species, DNA damage, autophagy, and caspase 3/7-mediated apoptotic cell death. While the conventional fractionated dose regimen of 20 Gy/10 f was effective at inducing cell death via the above mechanism, this was exceeded by a 20 Gy/4 f regimen which improved median survival and histopathology in Gl261-tumor bearing mice, and eradicated tumors in CT2A tumors with no additional toxicity. CONCLUSIONS: Spacing of hypofractionated RT doses 72 h apart showed increased median survival and tumor control via increased activation of RT-mediated cell death, with no observed increased in radiotoxicity. This supports further exploration of differential RT fractionated regimens in GB clinical trials to reduce delayed neurological radiotoxicity.

Computed tomography (CT)-defined sarcopenia and myosteatosis are prevalent in patients with neuroendocrine neoplasms (NENs) treated with peptide receptor radionuclide therapy (PRRT).

BACKGROUND/OBJECTIVES: Neuroendocrine neoplasms (NEN) may predispose patients to malnutrition. CT-defined sarcopenia and myosteatosis are common in other tumour types and recognized adverse prognostic factors. However, the prevalence and prognostic impact of sarcopenia and myosteatosis remain undetermined in NEN patients to date. METHODS: A retrospective study of NEN patients treated with peptide receptor radionuclide therapy (PRRT) at a tertiary institution from 2012 to 2017. Patients with PET/CT imaging at baseline and follow-up were included. The L3 slice of the co-localizing CT was analysed using the Alberta Protocol. Skeletal muscle cross-sectional area and muscle attenuation were measured and compared with pre-defined cut-offs. The primary endpoint was the prevalence of sarcopenia and myosteatosis according to previously published cut-offs. RESULTS: Fourty-nine patients (median age 64 (range 26-80) years) were included. The most common primary sites of tumour were the small bowel (51%) and pancreas (26%). Baseline sarcopenia was prevalent in 67% of patients and myosteatosis in 71%. Forty-five percent of patients gained weight over the course of PRRT. The presence of baseline sarcopenia was not associated with progression-free survival (20.8 mo vs. 20.7 mo, HR 0.86, p = 0.70) nor overall survival. Similarly, baseline myosteatosis (PFS 19.5 mo vs. 20.8 mo, HR 0.77, p = 0.47) was not significantly associated with survival outcomes. The mean (SD) age of those with myosteatosis was 60.8 ± 11.6 years compared to 49.7 ± 12.7 years for those without (p = 0.003). CONCLUSIONS: Body composition analysis is feasible using routinely acquired PET/CT data for patients with NEN. CT-defined sarcopenia and myosteatosis are prevalent in NEN patients, although myosteatosis is more common with increasing age. These findings were not associated with worsened overall or progression-free survival in the current study.

Glycolysis and Fatty Acid Oxidation Inhibition Improves Survival in Glioblastoma.

Glioblastoma (GBM) is the most aggressive adult glioma with a median survival of 14 months. While standard treatments (safe maximal resection, radiation, and temozolomide chemotherapy) have increased the median survival in favorable O(6)-methylguanine-DNA methyltransferase (MGMT)-methylated GBM (~21 months), a large proportion of patients experience a highly debilitating and rapidly fatal disease. This study examined GBM cellular energetic pathways and blockade using repurposed drugs: the glycolytic inhibitor, namely dicholoroacetate (DCA), and the partial fatty acid oxidation (FAO) inhibitor, namely ranolazine (Rano). Gene expression data show that GBM subtypes have similar glucose and FAO pathways, and GBM tumors have significant upregulation of enzymes in both pathways, compared to normal brain tissue (p < 0.01). DCA and the DCA/Rano combination showed reduced colony-forming activity of GBM and increased oxidative stress, DNA damage, autophagy, and apoptosis in vitro. In the orthotopic Gl261 and CT2A syngeneic murine models of GBM, DCA, Rano, and DCA/Rano increased median survival and induced focal tumor necrosis and hemorrhage. In conclusion, dual targeting of glycolytic and FAO metabolic pathways provides a viable treatment that warrants further investigation concurrently or as an adjuvant to standard chemoradiation for GBM.

Are In Vitro Human Blood-Brain-Tumor-Barriers Suitable Replacements for In Vivo Models of Brain Permeability for Novel Therapeutics?

BACKGROUND: High grade gliomas (HGG) are incapacitating and prematurely fatal diseases. To overcome the poor prognosis, novel therapies must overcome the selective and restricted permeability of the blood-brain barrier (BBB). This study critically evaluated whether in vitro human normal BBB and tumor BBB (BBTB) are suitable alternatives to "gold standard" in vivo models to determine brain permeability. METHODS: A systematic review utilizing the PRISMA guidelines used English and full-text articles from the past 5 years in the PubMed, Embase, Medline and Scopus databases. Experimental studies employing human cell lines were included. RESULTS: Of 1335 articles, the search identified 24 articles for evaluation after duplicates were removed. Eight in vitro and five in vivo models were identified with the advantages and disadvantages compared within and between models, and against patient clinical data where available. The greatest in vitro barrier integrity and stability, comparable to in vivo and clinical permeability data, were achieved in the presence of all cell types of the neurovascular unit: endothelial cells, astrocytes/glioma cells, pericytes and neurons. CONCLUSIONS: In vitro co-culture BBB models utilizing stem cell-derived or primary cells are a suitable proxy for brain permeability studies in order to reduce animal use in medical research.

Temporal and spatial modulation of the tumor and systemic immune response in the murine Gl261 glioma model.

Glioblastoma, the most aggressive form of glioma, has a 5-year survival rate of <5%. While radiation and immunotherapies are routinely studied in the murine Gl261 glioma model, little is known about its inherent immune response. This study quantifies the temporal and spatial localization of immune cell populations and mediators during glioma development. Eight-week old male C57Bl/6 mice were orthotopically inoculated with 1x106 Gl261 cells and tumor morphology, local and systemic immune cell populations, and plasma cytokines/chemokines assessed at day 0, 1, 3, 7, 14, and 21 post-inoculation by magnetic resonance imaging, chromogenic immunohistochemistry, multiplex immunofluorescent immunohistochemistry, flow cytometry and multiplex immunoassay respectively. From day 3 tumors were distinguishable with >30% Ki67 and increased tissue vascularization (p<0.05). Increasing tumor proliferation/malignancy and vascularization were associated with significant temporal changes in immune cell populations within the tumor (p<0.05) and systemic compartments (p = 0.02 to p<0.0001). Of note, at day 14 16/24 plasma cytokine/chemokines levels decreased coinciding with an increase in tumor cytotoxic T cells, natural killer and natural killer/T cells. Data derived provide baseline characterization of the local and systemic immune response during glioma development. They reveal that type II macrophages and myeloid-derived suppressor cells are more prevalent in tumors than regulatory T cells, highlighting these cell types for further therapeutic exploration.

Mass Cytometry Reveals a Sustained Reduction in CD16+ Natural Killer Cells Following Chemotherapy in Colorectal Cancer Patients.

The immune system and inflammation plays a significant role in tumour immune evasion enhancing disease progression and reducing survival in colorectal cancer (CRC). Patients with advanced stages of colorectal cancer will all undergo treatment with cytotoxic chemotherapy which may alter the complexity of immune cell populations. This study used mass cytometry to investigate the circulating immune cell profile of advanced CRC patients following acute and chronic doses of standard cytotoxic chemotherapy and analysed seven major immune cell populations and over 20 subpopulations. Unsupervised clustering analysis of the mass cytometry data revealed a decrease in NK cells following one cycle of cytotoxic chemotherapy. Investigation into the NK sub-population revealed a decline in the CD56dim CD16+ NK cell population following acute and chronic chemotherapy treatment. Further analysis into the frequency of the NK cell sub-populations during the long-term chemotherapy treatment revealed a shift in the sub-populations, with a decrease in the mature, cytotoxic CD56dim CD16+ accompanied by a significant increase in the less mature CD56dim CD16- and CD56bright NK cell populations. Furthermore, analysis of the phosphorylation status of signalling responses in the NK cells found significant differences in pERK, pP38, pSTAT3, and pSTAT5 between the patients and healthy volunteers and remained unchanged throughout the chemotherapy. Results from this study reveals that there is a sustained decrease in the mature CD16+ NK cell sub-population frequency following long-term chemotherapy which may have clinical implications in therapeutic decision making.

A Prospective Study of Circulating Tumor DNA to Guide Matched Targeted Therapy in Lung Cancers.

BACKGROUND: Liquid biopsy for plasma circulating tumor DNA (ctDNA) next-generation sequencing (NGS) is commercially available and increasingly adopted in clinical practice despite a paucity of prospective data to support its use. METHODS: Patients with advanced lung cancers who had no known oncogenic driver or developed resistance to current targeted therapy (n = 210) underwent plasma NGS, targeting 21 genes. A subset of patients had concurrent tissue NGS testing using a 468-gene panel (n = 106). Oncogenic driver detection, test turnaround time (TAT), concordance, and treatment response guided by plasma NGS were measured. All statistical tests were two-sided. RESULTS: Somatic mutations were detected in 64.3% (135/210) of patients. ctDNA detection was lower in patients who were on systemic therapy at the time of plasma collection compared with those who were not (30/70, 42.9% vs 105/140, 75.0%; OR = 0.26, 95% CI = 0.1 to 0.5, P < .001). The median TAT of plasma NGS was shorter than tissue NGS (9 vs 20 days; P < .001). Overall concordance, defined as the proportion of patients for whom at least one identical genomic alteration was identified in both tissue and plasma, was 56.6% (60/106, 95% CI = 46.6% to 66.2%). Among patients who tested plasma NGS positive, 89.6% (60/67; 95% CI = 79.7% to 95.7%) were also concordant on tissue NGS and 60.6% (60/99; 95% CI = 50.3% to 70.3%) vice versa. Patients who tested plasma NGS positive for oncogenic drivers had tissue NGS concordance of 96.1% (49/51, 95% CI = 86.5% to 99.5%), and directly led to matched targeted therapy in 21.9% (46/210) with clinical response. CONCLUSIONS: Plasma ctDNA NGS detected a variety of oncogenic drivers with a shorter TAT compared with tissue NGS and matched patients to targeted therapy with clinical response. Positive findings on plasma NGS were highly concordant with tissue NGS and can guide immediate therapy; however, a negative finding in plasma requires further testing. Our findings support the potential incorporation of plasma NGS into practice guidelines.

Sub-acute Toxicity in Non-cancerous Tissue and Immune-Related Adverse Events of a Novel Combination Therapy for Cancer.

Brain, lung, and colon tissue experience deleterious immune-related adverse events when immune-oncological agents or radiation are administered. However, there is a paucity of information regarding whether the addition of radiation to immuno-oncological regimens exacerbates the tissue inflammatory response. We used a murine model to evaluate sub-acute tissue damage and the systemic immune response in C57Bl/6 mice when administered systemic anti-programmed cell death protein 1 (αPD-1) immunotherapy alone or in combination with stereotactic fractionated 10 gray/5 X-ray radiation to normal brain, lung or colon tissue. The model indicated that combinatorial αPD-1 immunotherapy and radiation may alter normal colon cell proliferation and cerebral blood vasculature, and induce systemic thrombocytopenia, lymphopenia, immune suppression, and altered immune repertoire (including interleukin-1ß). Therein our data supports close monitoring of hematological and immune-related adverse events in patients receiving combination therapy.

Radiation, inflammation and the immune response in cancer.

Radiation is an important component of cancer treatment with more than half of all patients receive radiotherapy during their cancer experience. While the impact of radiation on tumour morphology is routinely examined in the pre-clinical and clinical setting, the impact of radiation on the tumour microenvironment and more specifically the inflammatory/immune response is less well characterised. Inflammation is a key contributor to short- and long-term cancer eradication, with significant tumour and normal tissue consequences. Therefore, the role of radiation in modulating the inflammatory response is highly topical given the current wave of targeted and immuno-therapeutic treatments for cancer. This review provides a general overview of how radiation modulates the inflammatory and immune response-(i) how radiation induces the inflammatory/immune system, (ii) the cellular changes that take place, (iii) how radiation dose delivery affects the immune response, and (iv) a discussion on research directions to improve patient survival, reduce side effects, improve quality of life, and reduce financial costs in the immediate future. Harnessing the benefits of radiation on the immune response will enhance its maximal therapeutic benefit and reduce radiation-induced toxicity.

A Longitudinal Investigation of Inflammatory Markers in Colorectal Cancer Patients Perioperatively Demonstrates Benefit in Serial Remeasurement.

OBJECTIVE: To characterize the longitudinal course of the systemic inflammatory response (SIR) throughout the perioperative period. To investigate whether postoperative changes in the neutrophil-to-lymphocyte ratio (NLR) or lymphocyte-to-monocyte ratio (LMR) when compared with preoperative levels ('conversion') are associated with survival differences in colorectal cancer patients undergoing resection. BACKGROUND: Recent evidence suggests that preoperative measurements of markers of the SIR including the NLR and LMR are prognostic. However, a few data exist evaluating longitudinal changes in the SIR especially in regards to their association with surgical interventions, optimal timing of assessment, and their effect on patient survival. METHODS: Data from 6 hospitals from January 1998 to December 2012 were retrospectively collected. We examined 2280 patients with complete data. For the subgroup analysis investigating conversion, we examined 587 patients with full preoperative and postoperative data from 21 to 56 days postoperative. Patients were stratified into 4 groups for analysis of conversion in a multivariate Cox-regression model. RESULTS: A longitudinal profile for the perioperative NLR and LMR was clearly characterized identifying an optimal period of remeasurement at 21 to 56 days postoperation. In multivariate analysis both NLR change group (P < 0.001) and LMR change group (P < 0.001) were independently associated with overall survival. For both biomarkers, patients with both a low preoperative and postoperative inflammatory state had the best survival. A change from the preoperative to postoperative inflammatory state was associated with a survival difference. CONCLUSIONS: This study characterizes the perioperative SIR profile and provides evidence for the remeasurement of SIR biomarkers postoperatively at 21 to 56 days for further prognostication.

Cancer-Related Systemic Inflammation: The Challenges and Therapeutic Opportunities for Personalized Medicine.

Over the last decade there has been significant progress towards the development of personalized or "precision" medicine for many patients with cancer. However, there still remain subpopulations of cancer patients that do not possess a tumor mutation profile that is successfully targeted by the newer molecular anticancer drugs and further personalized approaches are needed. The presence of cancer-related systemic inflammation represents an underappreciated subpopulation of cancer patients needing personalized therapy. For ∼25% of all advanced cancer patients, regardless of histological subtype, the patients with systemic inflammation have significantly poorer response to chemotherapy and also shorter overall survival compared to those cancer patients without inflammation. The development of cancer-related systemic inflammation involves interactions between host and tumor cells that are potential new drug targets in cancer chemotherapy. In this review we discuss the challenges and clinical opportunities to develop new therapeutic strategies for this underappreciated drug target.

Prognostic and predictive biomarkers in neuroendocrine tumours.

Neuroendocrine tumours are extremely heterogeneous malignancies. Despite marked heterogeneity in clinical course and prognosis, few biomarkers exist to help predict prognosis and guide treatment. Many tumour-based biomarkers (Ki-67, mitotic count, genetic/epigenetic changes and microRNAs) exist, but only Ki-67 and mitotic count have strong evidence to support their routine use. Blood-based markers are easily repeatable, but currently established biomarkers (chromogranin A and urinary 5-HIAA) are difficult to measure accurately in practice. Structural imaging is used routinely via the TNM system. Functional imaging such as 68Ga-based and FDG PET may become valuable biomarkers with their increasing availability, aided by ongoing quantitative research. Multiple nomograms have been proposed to integrate the above factors, but most have not been prospectively validated and are difficult to use in practice. Further research should aim to establish robust new biomarkers and integrate existing ones to help optimise NET treatment.

The Lymphocyte-to-Monocyte Ratio is a Superior Predictor of Overall Survival in Comparison to Established Biomarkers of Resectable Colorectal Cancer.

OBJECTIVE: The study aims to investigate the prognostic value of the lymphocyte-to-monocyte ratio (LMR) in patients with colorectal cancer (CRC) undergoing curative resection and to compare it to established biomarkers including the neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), modified Glasgow prognostic score (mGPS), and combined BRAF-mismatch repair (MMR) status. BACKGROUND: The prognostic significance of systemic inflammatory markers in CRC such as the NLR, PLR, and mGPS has been well defined. Commonly used genetic markers such as combined BRAF-MMR status have also been found to be prognostic. Recent evidence, although limited, suggests that the preoperative LMR may be prognostic in CRC. METHODS: Data from the Northern Sydney Local Health District from January 1998 to December 2012 were retrospectively collected. Of 3281 consecutive patients identified, 1623 patients who underwent curative resection were deemed eligible for inclusion. The relation between the LMR, clinicopathologic variables, and other biomarkers were analyzed in Kaplan-Meier log-rank survival analysis and then multivariate Cox regression models looking for association with overall survival (OS). RESULTS: In multivariate analysis of all patients, elevated LMR was associated with better OS (hazard ratio 0.569, 95% confidence interval: 0.478-0.677, P < 0.001) independent of age (P < 0.001), T stage (P < 0.001), N stage (P < 0.001), and grade (P = 0.049). The NLR, PLR, and combined BRAF-MMR status were not independently significant. In multivariate subgroup analysis of 389 patients with mGPS, LMR remained the only independently significant biomarker (hazard ratio 0.620, 95% confidence interval: 0.437-0.880, P = 0.007). CONCLUSIONS: The LMR is an independent predictor of OS in patients with CRC undergoing curative resection and appears to be superior to pre-existing biomarkers.

Cancer-related inflammation and treatment effectiveness.

Inflammation is a recognised hallmark of cancer that substantially contributes to the development and progression of malignancies. In established cancers, there is increasing evidence for the roles that local immune response and systemic inflammation have in progression of tumours and survival of patients with cancer. This knowledge provides an opportunity to target these inflammatory responses to improve patient outcomes. In this Review, we examine the complex interplay between local immune responses and systemic inflammation, and their influence on clinical outcomes, and propose potential anti-inflammatory interventions for patients with cancer.

Identification by NMR spectroscopy of the two stereoisomers of the platinum complex [PtCl2(S-ahaz)] (S-ahaz = 3(S)-aminohexahydroazepine) bound to a DNA 14-mer oligonucleotide. NMR evidence of structural alteration of a platinated A x T-rich 14-mer DNA duplex.

The enantiomers of the asymmetric, chiral platinum(II) complex [PtCl(2)(S-ahaz)] (S-ahaz = 3(S)-aminohexahydroazepine) each form two stereoisomers on binding to GpG sequences of DNA: one in which the primary amine is directed toward the 5' end of the DNA and one in which it is directed toward the 3' end. Previous binding studies have revealed that the S-enantiomer forms the two stereoisomers in a 7:1 ratio while the R-enantiomer forms them in close to a 1:1 ratio. In an attempt to elucidate the reasons behind the stereoselectivity displayed by the S-enantiomer and to establish which isomer is formed in the greater amount, we report here its reaction with a 14-mer oligodeoxyribonucleotide having a single GpG site. The two stereoisomers that formed were separated using HPLC methods, and their integrities were confirmed by electrospray ionization mass spectrometry. The DNA duplex was formed by combination of each of the purified reaction products with the complementary strand of DNA. Identification of both of the stereoisomers was achieved using 2D NMR spectroscopy, which is the first time this has been achieved for an unsymmetric platinum complex bound to DNA. The minor stereoisomer, with the bulk of the ahaz ring directed toward the 3' end of the platinated strand, induced considerable disruption to the 14-mer DNA duplex structure. The primary amine of the ahaz ligand was oriented toward the 3' side of the duplex in the major isomer, giving a DNA structure that was less disrupted and was more akin to the structure of the DNA on binding of cisplatin to the same sequence.

Synthesis, characterisation and in vitro cytotoxicity studies of a series of chiral platinum(II) complexes based on the 2-aminomethylpyrrolidine ligand: X-ray crystal structure of [PtCl2(R-dimepyrr)] (R-dimepyrr=N-dimethyl-2(R)-aminomethylpyrrolidine).

A series of platinum(II) complexes were synthesised based on the enantiomerically pure amino acid proline. Novel synthetic pathways were developed, adapted from standard peptide chemistry, to produce the 2-aminomethylpyrrolidine (pyrr) ligand and its derivatives with differing arrangements of methyl substituents at the exocyclic amine sites. The crystal structure of [PtCl(2)(R-dimepyrr)] (R-dimepyrr=N,N-dimethyl-2(R)-aminomethylpyrrolidine) is reported and the five-membered ligand ring has been shown to be in an envelope conformation. Cytotoxicity studies were carried out on the ovarian cancer A2780 tumour cell line and its cisplatin-resistant variant, A2780cisR. Remarkably good activity was seen for several of the drugs when compared to cisplatin despite the addition of substantial steric bulk to the amine groups, and there was a lack of cross-resistance with cisplatin seen for some compounds.