Abstract 4037: The pattern of extracellular vesicles secretion and their role in head and neck squamous cell carcinoma

Head and Neck Squamous Cell Carcinoma (HNSCC) is a keratinocytic neoplasm that is considered to be one of the six most common malignancies worldwide. It represents more than 90% of all cancers that occur throughout the upper aerodigestive tract. Unfortunately, HNSCC is still related to a high rate of morbidity and mortality. The poor prognosis of HNSCC shows remarkable association with local invasion and subsequent metastasis. Recent evidences have shown that the tumor development and the metastatic process are supported by extracellular vesicles (EVs), which are released from the tumor cells to the blood or lymphatic system. The molecular mechanisms involved in EVs biogenesis and secretion are, however, poorly understood. Herein, we sought to evaluate the pathways that govern EVs formation and the crucial mechanism that regulates EVs’ release by HNSCC cells. In addition, we tried to recognize the role of HNSCC EVs upon dysplastic keratinocytes and microenvironment cells such as endothelial cells. EVs derived from three HNSCC cell lines (SCC-9, Cal27 and FaDu) were isolated by ultracentrifugation and quantified using Nanoparticle Tracking Analysis (NTA - NanoSight®). A screen targeting for the components of EVs’ biogenesis in the HNSCC cell lines through western blotting was also performed and lysosomal compartment was followed by immunofluorescence in live cells. Finally, the invasion and angiogenic potential of dysplastic keratinocytes (DOK cell line) and endothelial cells (HUVEC cell line) were evaluated, respectively, after treatment with EVs secreted by HNSCC cell lines. Comparing the three cell lines, FaDu cells presented higher expression of proteins responsible for EVs formation (p<0.05), such as Flotilin-1, Tsg101, VPS36 and also Rab7, a small GTPase that directs vesicles to lysosomes. However, FaDu cells secreted less EVs than SCC-9 and Cal27, as well as it showed lower levels of Vps4, required for formation of multivesicular bodies. Immunofluorescence experiments showed the presence of numerous perinuclear clusters positive for LAMP-1 (lysosome marker) in FaDu and Cal27 cells, while SCC-9 showed LAMP1-positive organelles dispersed throughout its cytoplasm. These findings indicate that the majority of EVs formed by FaDu cells can be driven to lysosome compartment instead of being released to the extracellular milieu. Interestingly, when DOK and HUVEC cells were treated with the same number of EVs derived from HNSCC cell lines, SCC-9 EVs enhanced the invasion and angiogenic potential of keratinocytes and endothelial cells, respectively. Taken together, our data highlights a possible role for Rab7 protein in the negative regulation of EVs secretion by HNSCC cell lines. Moreover, the results provided by the in vitro functional assays suggest the clinical importance of regulating EVs secretion for the controlling of HNSCC tumor aggressivenes.

Citation Format: Fernanda S. Giudice, Bruna R. Rodrigues, Tonielli C. Lacerda, Rodrigo T. Cartaxo, Antuani R. Baptistella, Marcos V. S. Dias, Luiz P. Kowalski, Vilma R. Martins. The pattern of extracellular vesicles secretion and their role in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4037. doi:10.1158/1538-7445.AM2015-4037

Abstract 4444: The role of small GTPase Rab7 in the secretion of extracellular microvesicles by head and neck squamous cells carcinoma

Head and neck squamous cell carcinoma (HNSCC) is an epithelial malignant tumor that shows its highest incidence in the upper aerodigestive tract and is considered one of the six most common malignancies worldwide. Among the processes involved in the poor prognosis of HNSCC, local invasion and subsequent metastasis are the most important events. Recent evidences have shown that metastasis can be the result of extracellular microvesicles (MVEs) being released from the tumor cells to the blood or lymphatic system. The molecular mechanisms involved in MVEs biogenesis and secretion are, however, poorly understood. Herein, we have performed a screen targeting for the components of MVEs biogenesis in three HNSCC cell lines (SCC-9, Cal27 and FaDu) through western blotting. MVEs were quantified using Nanoparticle Tracking Analysis (NTA - NanoSight®) and the lysosomal compartment was followed in the cell lines through immunofluorescence. Comparing the three cell lines, FaDu cells presented higher expression of proteins responsible for MVEs formation (p<0.05), such as Flotilin-1, Tsg101, VPS36 and also Rab7, a small GTPase that directs vesicles to lysosomes. However, FaDu cells secreted less MVEs than SCC-9 and Cal27. Immunofluorescence experiments showed the presence of numerous perinuclear clusters positive to LAMP-1 (lysosome marker) in FaDu cells, while SCC-9 and Cal27 showed LAMP1-positive organelles dispersed throughout their cytoplasms. Taken together, the results highlight a role for Rab7 protein in the negative regulation of MVEs secretion by HNSCC cell lines, which may provide important information related to tumor progression, treatment response, and especially the development of metastasis.

Supported by São Paulo Research Foundation (FAPESP)

Citation Format: Fernanda S. Giudice, Bruna R. Rodrigues, Marcos V. S. Dias, Antuani R. Baptistella, Tonielli Cristina S. Lacerda, Luiz P. Kowalski, Vilma R. Martins. The role of small GTPase Rab7 in the secretion of extracellular microvesicles by head and neck squamous cells carcinoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4444. doi:10.1158/1538-7445.AM2014-4444

Abstract 3942: Cell death resistance promoted by radiotherapy in a colorectal cell line

Colorectal adenocarcinoma is the fourth more frequent cause of death by cancer in the world. Despite some similarities, the rectal cancer has characteristics that differentiate it from the colon cancer, resulting in different treatments and outcomes. The rectal cancer in stages II and III is treated with neoadjuvant chemoradiation followed by surgery, and the response to neoadjuvant treatment in patients is variable and unpredictable. Up to now, surgery intervention is required to assess the pathologic response to therapy. The identification of predictive biomarkers for response to therapy is of great importance, in order to identify the patients that will benefit from such treatment. To better understand the molecular alterations in cells that resist to the radiotherapy, we started our research using WiDr, a colon tumor cell line. Cell cycle synchronized WiDr cells were submitted to two cycles of irradiation (4Gy in each cycle and 2 week of interval between the cycles) and resistant cells were isolated. Irradiated WiDr cells (RxTWiDr) shown a better capacity to form colonies, in colony growth assays, when compared to parental WiDr cells. This characteristic was maintained when they were submitted to a new round of irradiation. In addition, WiDrRxT cells treated with Staurosporine presented a higher viability in MTT assays than WiDr cells. We also collected the conditioned medium (CM) from RxTWiDr and WiDr cells, and treated the parental WiDr cells. The parental cells treated with CM from RxTWiDr cells for 15 minutes shown an increase in the ERK1/2 activation when compared to cells treated CM from WiDr cells. These results demonstrated that radio resistant cells are more resilient than parental cells and that their secreted factors activated specific signaling pathways via ERK1/2 phosphorylation. The nature of these factors is under investigation using proteomics.

Supported by São Paulo State Foundation (FAPESP)

Citation Format: Antuani R. Baptistella, Bruna Rodrigues, Marcos Dias, Fernanda Giudice, Tonielli Lacerda, Tiago Santos, Felipe Silva, Petrus Paulo Silva, Samuel Aguiar, Vilma Martins. Cell death resistance promoted by radiotherapy in a colorectal cell line. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3942. doi:10.1158/1538-7445.AM2014-3942

Abstract 4880: Regulation of extracellular microvesicles secretion by Rab27b in glioblastoma multiforme

Background: Glioblastoma multiforme (GBM) is the most malignant form of astrocytomas and they release a heterogeneous population of microvesicles (MVEs) to the extracellular space. These MVEs are involved in intercellular communication by carrying oncogenes, and miRNAs that contribute with the tumor aggressiveness. However, the mechanisms of MVEs biogenesis and secretion in GBM are poorly understood.

Material and Methods: Using five glioblastoma cell lines (LN-18, LN-229, U87MG, A-172 and U118MG) the vesicular biogenesis was characterize analyzing the expression of markers involved in steps of this process by western blotting. MVEs were also quantified using Nanoparticle Tracking Analysis (NTA - NanoSight®). Immunofluorescence was performed in these cell lines to characterize the cellular distribution of Rab27b, which is responsible for driving the multivesicular bodies to the plasma membrane. Immunohistochemistry (IHC) measured Rab27b expression in a tissue microarray with 60 GBMs samples and 13 non-neoplastic human brain tissues used as controls. IHC intensity was scored from 1 to 3 (1 weak; 2, moderate; 3, strong) and positive cells, from 0 to 3 (0, 0%; 1, 1-10%+; 2, 11-50%+; 3, ≥ 51%+). The final IHC score was represented by intensity + positivity. Student's t-test was performed to compare Rab27b expression in GBM and non neoplastic tissues. Kaplan-Meier and log-rank tests were used to correlate overall survival with Rab27b expression.

Results: The cell lines showed a heterogeneous expression of markers involved in vesicle biogenesis. LN-18 cells presented higher levels of Cavelin-1, Flotillin -1, Alix and VPS4, p<0.01, but lower levels of Rab27b, p<0.0001. On the other hand, the U87MG cells standed out by higher levels of Rab27b, compared to the other cell lines studied, p<0.0001. Interesting, our results pointed that MVEs secretion is directed correlated to the expression pattern of Rab27b in GBM cells. Indeed, LN-18 cells showed lower levels of MVEs secretion (p<0.001) while U87MG cells presented higher MVEs secretion, p<0.001. In addition, Rab27b and CD63 (MVEs marker) were retained in the perinuclear region of LN -18 cells while in U87MG cells both proteins were distributed throughout the cytoplasm. Finally, Rab27b is overexpressed in GBM samples when compared to non-neoplastic tissue and patients presenting high expression of Rab27b showed lower survival outcomes.

Conclusions: Our findings suggest that Rab27b may be crucial to the secretion of MVEs process in GBM. Furthermore, the overexpression of Rab27b in glioblastoma patients coincides with a poor prognostic phenotype.

Supported by São Paulo State Foundation (FAPESP).

Citation Format: Bruna R. Rodrigues, Fernanda S. Giudice, Marcos S. Dias, Antuani R. Baptistella, Rafael R. Malagoli, Paulo I. Sanematsu, Sergio Suzuki, Mariana Reis, Vilma R. Martins. Regulation of extracellular microvesicles secretion by Rab27b in glioblastoma multiforme. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4880. doi:10.1158/1538-7445.AM2014-4880