Abstract 2966: Novel ex vivo model for ERα positive breast cancer

Three-dimensional ex vivo cultures from patient-derived tumor tissue offer new opportunities for drug development and personalized treatment of cancer. However, one of the main challenges in establishing a tumor type faithful ex vivo tissue culture system is in optimization of biochemical and physical microenvironment to preserve desired phenotypic features. A collaboration with the Helsinki University Hospital enables us to receive live patient-derived breast cancer tissue samples from most breast cancer surgeries performed in the Southern Finland, typically samples arriving twice a week. Together with a group of materials scientists from Aalto Technical University we have explored seven different 3D culture matrices and defined their biomechanical properties and stiffness values with rheological measurements. Four investigated matrices preserved the luminal CK8+ cell phenotype of the luminal cancers they derived from, whereas rest of the matrices that included commonly used Matrigel and collagen scaffolds promoted a switch in the cell identity from luminal CK8+ to basal CK14+ phenotype. Furthermore, the genetic expression profiles examined with NGS corresponded to observed phenotypic switch. We noticed significant species-specific differences between mouse mammary and human breast samples in their morphology, phenotypic responses and ERα+ preservation to microenvironmental matrix stiffness. Furthermore, a combination of scaffold stiffness and composition of biochemical matrix constituency is required for long-term maintenance of ERα+ luminal tumour phenotype. Therefore, both physical properties and composition of the microenvironment need to be optimized for maintenance of breast tumor type specific phenotype and genetic profiles of ex vivo tumor explant cultures.

Citation Format: Pauliina M. Munne, Lahja Martikainen, Iiris Räty, Kia Bertula, Nonappa Nonappa, Aino Peura, Minna Mutka, Marjut Leidenius, Tuomo Meretoja, Panu Kovanen, Johanna Mattson, Paivi Heikkila, Heikki Joensuu, Olli Ikkala, Juha T. Klefstrom. Novel ex vivo model for ERα positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2966.

Abstract LB-189: Pharmacological reactivation of MYC-dependent apoptosis cooperates with anti-PD1 immunotherapy

Elevated MYC levels sensitize tumor cells to apoptosis but the therapeutic potential of this mechanism remains unclear. We find, in a model of MYC-driven breast cancer, that pharmacological activation of AMPK dramatically synergizes with BCL-2/BCL-XL inhibitors to activate MYC-dependent apoptosis. We demonstrate the translational potential of an AMPK and BCL- 2/BCL-XL co-targeting strategy in ex vivo and in vivo models of MYC-high breast cancer. Metformin combined with either navitoclax or venetoclax efficiently inhibits tumor growth, confers survival benefits and induces tumor infiltration by immune cells. However, withdrawal of the drugs allowed tumor re- growth with presentation of PD1+/CD8+ T cell infiltrates, suggesting immune escape. A two-step treatment regimen, beginning with neoadjuvant metformin+venetoclax to induce apoptosis and followed by tumor resection and adjuvant metformin+venetoclax+anti-PD1 treatment to overcome immune escape, led to durable antitumor responses even after drug withdrawal. We demonstrate that pharmacological reactivation of MYC-dependent apoptosis is a powerful antitumor strategy involving both tumor cell depletion and immunosurveillance.

Citation Format: Heidi M. Haikala, Johanna M. Anttila, Mariel Savelius, Elsa Marques, Tiina Raatikainen, Mette Ilander, Henna Hakanen, Johanna Mattson, Paivi Heikkila, Marjut Leidenius, Heikki Joensuu, Satu Mustjoki, Panu Kovanen, Martin Eilers, Joel D. Leverson, Juha T. Klefström. Pharmacological reactivation of MYC-dependent apoptosis cooperates with anti-PD1 immunotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-189.

Metastasis to sentinel lymph nodes in breast cancer is associated with maturation arrest of dendritic cells and poor co-localization of dendritic cells and CD8+ T cells

The regional immune systems of patients with breast cancer are immunosuppressed. Dendritic cells are professional antigen-presenting cells and present cancer-associated antigens to the adaptive immune system in sentinel lymph nodes. Dendritic cells may promote, or inhibit, an adaptive immune response to specific antigens. Our aim was to assess whether dendritic cells were associated with nodal metastasis in patients with breast cancer. Sentinel lymph nodes of 47 patients with breast cancer with varying degrees of nodal disease and ten controls were evaluated using immunohistochemistry for the accumulation of dendritic cells in general (CD1a(+)), mature dendritic cells (CD208(+)), and plasmacytoid dendritic cells (CD123(+)). Cytotoxic T cell and regulatory T cell accumulation were also evaluated. Sentinel lymph nodes with macrometastases demonstrated fewer mature dendritic cells than sentinel lymph nodes without metastasis (p = 0.028), but not controls. There were fewer mature dendritic cells to cytotoxic T cells in sentinel lymph nodes with metastasis than those without (p = 0.033). Also, there were more regulatory T cells to mature dendritic cells in sentinel lymph nodes with metastasis than those without (p = 0.02). In conclusion, our study suggests that sentinel lymph nodes with metastasis have arrest of maturation of dendritic cells, fewer mature dendritic cell interactions with cytotoxic T cells, and more regulatory T cells than sentinel lymph nodes without metastasis in patients with breast cancer. These findings extend our understanding of regional immunosuppression and suggest that most regional immunosuppressive changes are associated with nodal metastasis in breast cancer.

Chromosome 5 imbalance mapping in breast tumors from BRCA1 and BRCA2 mutation carriers and sporadic breast tumors

Comparative genomic hybridization (CGH) analysis has shown that chromosome 5q deletions are the most frequent aberration in breast tumors from BRCA1 mutation carriers. To map the location of putative 5q tumor suppressor gene(s), 26 microsatellite markers covering chromosome 5 were used in loss of heterozygosity (LOH) analysis of breast tumors from BRCA1 (n = 42) and BRCA2 mutation carriers (n = 67), as well as in sporadic cases (n = 65). High-density array CGH was also used to map chromosome 5 imbalance in 10 BRCA1 tumors. A high LOH frequency was found in BRCA1 tumors (range 19-82%), as compared to BRCA2 and sporadic tumors (ranges 11-44% and 7-43%, respectively). In all, 11 distinct chromosome 5 regions with LOH were observed, the most frequent being 5q35.3 (82%), 5q14.2 (71%) and 5q33.1 (69%) in BRCA1 tumors; 5q35.3 (44%), 5q31.3 (43%) and 5q13.3 (43%) in BRCA2 tumors and 5q31.3 (43%) in sporadic tumors. Array CGH analysis confirmed the very high frequency of 5q deletions, including candidate tumor suppressor genes such as XRCC4, RAD50, RASA1, APC and PPP2R2B. In addition, 2 distinct homozygous deletions were identified, spanning regions of 0.7-1.5 Mbp on 5q12.1 and 5q12.3-q13.1, respectively. These regions include only a few genes, most notably BRCC3/DEPDC1B (pleckstrin/G protein interacting and RhoGAP domains) and PIK3R1 (PI3 kinase P85 regulatory subunit). Significant association (p < or = 0.05) was found between LOH at certain 5q regions and factors of poor prognosis, including negative estrogen and progesterone receptor status, high grade, large tumor size and high portion of cells in S-phase. In conclusion, our results confirm a very high prevalence of chromosome 5q alterations in BRCA1 tumors, pinpointing new regions and genes that should be further investigated.

Discrepancies in current practice of pathological evaluation of sentinel lymph nodes in breast cancer. Results of a questionnaire based survey by the European Working Group for Breast Screening Pathology

AIMS

To evaluate aspects of the current practice of sentinel lymph node (SLN) pathology in breast cancer via a questionnaire based survey, to recognise major issues that the European guidelines for mammography screening should address in the next revision.

METHODS

A questionnaire was circulated by mail or electronically by the authors in their respective countries. Replies from pathology units dealing with SLN specimens were evaluated further.

RESULTS

Of the 382 respondents, 240 European pathology units were dealing with SLN specimens. Sixty per cent of these units carried out intraoperative assessment, most commonly consisting of frozen sections. Most units slice larger SLNs into pieces and only 12% assess these slices on a single haematoxylin and eosin (HE) stained slide. Seventy one per cent of the units routinely use immunohistochemistry in all cases negative by HE. The terms micrometastasis, submicrometastasis, and isolated tumour cells (ITCs) are used in 93%, 22%, and 71% of units, respectively, but have a rather heterogeneous interpretation. Molecular SLN staging was reported by only 10 units (4%). Most institutions have their own guidelines for SLN processing, but some countries also have well recognised national guidelines.

CONCLUSIONS

Pathological examination of SLNs throughout Europe varies considerably and is not standardised. The European guidelines should focus on standardising examination. They should recommend techniques that identify metastases > 2 mm as a minimum standard. Uniform reporting of additional findings may also be important, because micrometastases and ITCs may in the future be shown to have clinical relevance.

Consistency of staining and reporting of oestrogen receptor immunocytochemistry within the European Union—an inter-laboratory study

To assess the variability of oestrogen receptor (ER) testing using immunocytochemistry, centrally stained and unstained slides from breast cancers were circulated to the members of the European Working Group for Breast Screening Pathology, who were asked to report on both slides. The results showed that there was almost complete concordance among readers (kappa=0.95) in ER-negative tumours on the stained slide and excellent concordance among readers (kappa=0.82) on the slides stained in each individual laboratory. Tumours showing strong positivity were reasonably well assessed (kappa=0.57 and 0.4, respectively), but there was less concordance in tumours with moderate and low levels of ER, especially when these were heterogeneous in their staining. Because of the variation, the Working Group recommends that laboratories performing these stains should take part in a external quality assurance scheme for immunocytochemistry, should include a tumour with low ER levels as a weak positive control and should audit the percentage positive tumours in their laboratory against the accepted norms annually. The Quick score method of receptor assessment may also have too many categories for good concordance, and grouping of these into fewer categories may remove some of the variation among laboratories.

Pathological work-up of sentinel lymph nodes in breast cancer. Review of current data to be considered for the formulation of guidelines

Controversies and inconsistencies regarding the pathological work-up of sentinel lymph nodes (SNs) led the European Working Group for Breast Screening Pathology (EWGBSP) to review published data and current evidence that can promote the formulation of European guidelines for the pathological work-up of SNs. After an evaluation of the accuracy of SN biopsy as a staging procedure, the yields of different sectioning methods and the immunohistochemical detection of metastatic cells are reviewed. Currently published data do not allow the significance of micrometastases or isolated tumour cells to be established, but it is suggested that approximately 18% of the cases may be associated with further nodal (non-SN) metastases, i.e. approximately 2% of all patients initially staged by SN biopsy. The methods for the intraoperative and molecular assessment of SNs are also surveyed.

T-cell-mediated mucosal immunity is attenuated in experimental necrotizing enterocolitis

In premature infants with necrotizing enterocolitis (NEC) the gastrointestinal mucosal barrier is immature, but little is known about the immune response of immature bowel. The aim of this study was to evaluate the intestinal mucosal immune response in experimental NEC. In general anaesthesia, NEC was induced in six newborn piglets by injection of bovine casein into terminal ileum. Six controls received an equal amount of saline. Four hours later, samples were taken from the macroscopically most affected part of the treated loop and from the macroscopically healthy untreated intestine. Monoclonal antibodies to porcine CD1, CD2, CD4, CD8, CD45 and IgM were used for immunohistochemical staining. Casein-treated bowel showed typical macro- and microscopic findings of NEC. No changes were found in the saline-treated bowel. In both groups the bowel outside the treatment sector was normal. In casein-treated animals, treated samples showed significant decrease in density of CD4+ cells when compared with saline-treated controls. Similar trend was found in CD2+ and CD8+ cells but without statistical significance. Macroscopically healthy proximal untreated samples showed significant decrease in densities of CD2+, CD4+ and CD8+ lymphocytes in casein-treated group when compared with control samples. In casein-treated animals the density of CD45+ cells in the non-injected bowel was also decreased, but this did not reach statistical significance. Densities of CD1+ and IgM+ cells did not differ between casein-treated and saline-treated groups. A significant T-cell decrease was found in the present NEC model. Surprisingly, this was most prominent in the macroscopically healthy bowel outside the casein injection segment. The reason for T-cell decrease remains unclear, but bovine casein is known to contain peptide fractions that can modulate immune function. These findings may have implications in the design of neonatal milk formulas.

Somatic deletions in hereditary breast cancers implicate 13q21 as a putative novel breast cancer susceptibility locus

A significant proportion of familial breast cancers cannot be explained by mutations in the BRCA1 or BRCA2 genes. We applied a strategy to identify predisposition loci for breast cancer by using mathematical models to identify early somatic genetic deletions in tumor tissues followed by targeted linkage analysis. Comparative genomic hybridization was used to study 61 breast tumors from 37 breast cancer families with no identified BRCA1 or BRCA2 mutations. Branching and phylogenetic tree models predicted that loss of 13q was one of the earliest genetic events in hereditary cancers. In a Swedish family with five breast cancer cases, all analyzed tumors showed distinct 13q deletions, with the minimal region of loss at 13q21-q22. Genotyping revealed segregation of a shared 13q21 germ-line haplotype in the family. Targeted linkage analysis was carried out in a set of 77 Finnish, Icelandic, and Swedish breast cancer families with no detected BRCA1 and BRCA2 mutations. A maximum parametric two-point logarithm of odds score of 2.76 was obtained for a marker at 13q21 (D13S1308, theta = 0.10). The multipoint logarithm of odds score under heterogeneity was 3.46. The results were further evaluated by simulation to assess the probability of obtaining significant evidence in favor of linkage by chance as well as to take into account the possible influence of the BRCA2 locus, located at a recombination fraction of 0.25 from the new locus. The simulation substantiated the evidence of linkage at D13S1308 (P < 0.0017). The results warrant studies of this putative breast cancer predisposition locus in other populations.

Adenovirus-mediated gene transfer into kidney glomeruli using an ex vivo and in vivo kidney perfusion system - first steps towards gene therapy of Alport syndrome

In order to develop gene therapy for Alport syndrome, we have examined the efficiency of adenovirus-mediated transfer of the beta-galactosidase gene into cultured cells and intact glomeruli in vitro, and developed an organ perfusion system for gene transfer into kidney ex vivo and in vivo. Human endothelial and mesangial cells, as well as isolated human glomeruli, were readily infected and exhibited expression of the reporter gene. Single or multiple injections of the virus solution into the renal artery of pig in vivo did not lead to significant gene transfer and expression of the reporter gene in kidney cells. To increase the exposure time of kidney cells to the virus we perfused kidneys ex vivo and in vivo for up to 12 and 2 h, respectively. The perfusion system consisted of a perfusate container, a peristaltic pump and an artificial membrane lung gassed with carbogen. Using this system, intense expression of the reporter gene could be achieved in up to about 85% of the glomeruli after perfusion of an explanted kidney ex vivo and about the same efficiency of gene transfer could be obtained in glomerular cells after 2-h perfusion in vivo. Some expression was observed in other vascular endothelial cells following the perfusion, but no expression was observed in cells of the Bowman's capsule or epithelial cells of the tubuli. The X chromosome-linked form of Alport syndrome is caused by defects in the gene for the type IV collagen of alpha5 chain, which is primarily expressed in the kidney in glomerular cells. The present results demonstrated that efficient gene transfer can be achieved into glomerular cells, a prerequisite for gene therapy of this disease. The organ perfusion method developed in this study might also be applicable for gene therapy of other diseases.