ESTRO 37 Abstract book

ESTRO 37

S592

Material and Methods We selected 20 patients. Proteins involved in the apoptotic cascade (Bax, Caspases -3 and -9) were studied before and after 12 Gy in neoplastic tissues, high grade PIN areas and in healthy prostate cells. Immunofluorescent detection of antigens (anti-Bax, anti- caspases-3 and -9), were performed on bioptic sample and on surgical specimens 5-mm slices. Before and after IORT, also Bcl-2, p53, and ki-67 with immunoistochimical analysis were detected. A count of positive spots for immunofluorescence (Bax+, Caspases-3 and -9+/all nuclei) was performed on tumour cells, PIN and healthy tissue areas. Bax and caspases immunofluorescent positivity was compared in different areas and in neoplastic areas before and after single shot high dose Results Before IORT, mean Bcl-2 in neoplastic cells is 2.23% (range: 1-23), mean ki-67 in neoplastic area is 4.5% (range: 1-17) and mean p53 is 22.5% (1-36). After IORT mean Bcl-2 in neoplastic cells is 8.85% (range: 1-28), mean ki-67 in neoplastic area is 7.8% (range: 1-18) and mean p53 is 24.9% (1-94). A significant increase in Bax expression was detected in tumour and PIN areas comparing treated and untreated samples (p<0.05). After 12 Gy-single dose, healthy areas expressed significantly lower level of Bax positive with respect to neoplastic cells (p<0.0001), while in PIN areas, Bax positive cells were significantly more present than in neoplastic areas (p=0.0001). Results about Caspases 3 and 9 were conflicting and we did not find significant differences in expression between neoplastic and healthy tissue cells after IORT. With multivariate analysis, we find that cancer cells with ki-67 ≥ 8% show a trend toward greater expression of Bax (p=0.0641). We do not find correlations between ki-67 and caspases activation. We also found an increasing in Bcl-2 expression after IORT in neoplastic areas (p=0.0041); with multivariate analysis, we found that neoplastic cells with higher Bcl-2 expression after IORT had a worsen local control with higher incidence in biochemical failure. Bioptic specimens with p53 higher than 18% and ki-67 higher than 8% had worst post- operative staging with higher incidence in extracapsular invasion (p<0.05) and nodal positivity (p<0.05) Conclusion After 12 Gy, Bax is overexpressed in tumour and PIN cells. PIN areas seem to be more radiosensitive than neoplastic areas and healthy cells do not activate apoptosis after single dose, showing an intrinsic radioresistance. Pre-operative ki-67 and p53 definition could be use in clinical practice to predict patients with worsen pathological stage, while Bcl-2 activation after IORT might be predictive factor for loco-regional failure. At the best of our knowledge, this is the first study that correlated clinical parameters with pathology and apoptotic factors

Biology Research Center, Taoyuan, Taiwan 3 Chang Gung University, Department of Medical Imaging and Radiological Science, Taoyuan, Taiwan Purpose or Objective To study the role of MLK4 oncoprotein in the invasiveness of breast cancer and its response to ionizing radiation (IR). Material and Methods The expression and association of MLK4 in different sub- type breast cancer was first examined. By employing MLK4-knockdown technologies of short-hairpin RNA and clustered regularly interspaced short palindromic repeats (CRISPR) specifically targeting to MLK4, we performed the functional assessment of MLK4 in proliferation, invasiveness and migration in MLK4 expressing cell lines. The dose-response of MLK4 expression after ionizing radiation and its association with subtype was studied . Results Our data demonstrated that MLK4 protein expresses predominantly in triple-negative breast cancers (TNBCs) and is less present in other breast cancer like luminal, HER2 and normal-like subtypes. In addition, we have also identified that the presence of MLK4 is critical in cellular proliferation, invasion and migration of TNBCs but not other breast cancer subtypes, suggesting role of MLK4 in mediating breast cancer aggressiveness is subtype- specific. The importance of MLK4 in regulating the above- mentioned phenotypic behaviors of TNBCs was further confirmed by employing MLK4-knockdown technologies. The MLK4 appears to correlate with cancer stemness as our 3D mammosphere culture in MLK4-expressing breast cancer cells was compromised by MLK4-knockdown. MLK4 expression can be up-regulated upon IR in the most invasive TNBCs and the proportion of stem cell population is increased after IR, by a dose-dependent manner. Conclusion MLK4 is highly expressed in triple-negative breast cancers (TNBCs) and associated with the cancer cell proliferation, invasiveness, migration and stemness. It is exclusively radiation-inducible in TNBCs but not other subtypes of breast cancer. Our results suggest that MLK4 plays an important role in tumor biology and radiation biology of breast cancer and could be a potential therapeutic target for TNBCs. PO-1054 Wound fluids from patients after IORT abrogates epithelial-mesenchymal transition in breast cancer K. Kulcenty 1,2 , I. Piotrowski 2 , D. Murawa 3 , W. Suchorska 2,4 1 Greater Poland Cancer Centre, Radiobiology Laboratory- Department of Medical Physics, Poznan, Poland 2 University of Medical Sciences, Department of Electroradiology, Poznań, Poland 3 Greater Poland Cancer Centre, First Clinic of Surgical Oncology and General Surgery, Poznań, Poland 4 Greater Poland Cancer Centre, Radiobiology Laboratory- Department of Medical Physics, Poznań, Poland Purpose or Objective After breast cancer surgery, more than 90% of local recurrences occur in the same quadrant as the primary cancer. Wound fluids (WF) are believed to play a role in this process by inducing an inflammatory process in the scar tissue area, thereby modifying the tumor microenvironment. Given that most metastatic lesions occur within or near the scar tissue area, researchers have investigated whether localized radiotherapy, such as intraoperative radiotherapy (IORT), could be more

Poster: Radiobiology track: Radiobiology of breast cancer

PO-1053 A new radiation-inducible oncoprotein MLK4 and its role in in mediating breast cancer invasiveness J.H. Hong 1 , C.L. Lee 2 , Y.Y. Shih 3 1 Chang Gung Memorial Hospital, Radiation Oncology, Taoyuan, Taiwan 2 Institute for Radiological Research- Chang Gung Memorial Hospital/Chang Gung University, Radiation