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Leda H. Raptis PhD
 Leda H. Raptis
Position(s)
Professor
Contact Info
613-533-2462

For information on breast cancer, please visit https://breastcancer530667969.wordpress.com/

Education

Ph.D: University of Sherbrooke, supervised by Dr. Pierre Bourgaux, 1979

Postdoctoral Training:

  • Princeton University, supervised by Dr. Jane Flint
  • Harvard University, supervised by Dr. Thomas Benjamin

Research Interests

  1. Signal transduction in transformation and adipocytic differentiation.  a)  Ras, b) Stat3
  2. Electroporation of adherent cells in situ

Details of Research Interests:

Cellular interactions with neighbouring cells profoundly influence a variety of signalling events involved in mitogenesis, survival and differentiation.  Unlike tissue-culture cells, cells in a tumor have extensive opportunities for adhesion to their neighbours in a three-dimensional structure, therefore in the study of these processes it is important to take into account the effect of surrounding cells.  Cadherins recently emerged as a group of cell-cell adhesion molecules playing a key role in the regulation of signalling events as well as the maintenance of tissue architecture.

Our lab has recently demonstrated that engagement of E-cadherin can lead to a dramatic increase in the activity of Stat3, a protein often abnormally activated in cancer.  Most importantly, Stat3 activation was independent from a number of tyrosine kinases, including the Src family, IGF1-R, EGFR and Fer, often activated in many cancers. This novel  pathway could be a promising target in the treatment of cancers which may be independent from most tyrosine kinase oncogenes known to be activated in many cancers. Our recent work deals with the elucidation of this novel mechanism.  We are using two different approaches: 

1. Downregulation of expression of specific cellular genes through the introduction of an anti-message, dominant-negative mutants or siRNA, to demonstrate the overall involvement of a gene product.

2. Introduction of peptides corresponding to the proteins' point(s) of contact using a novel apparatus, to more specifically pinpoint the areas involved.

The reduction in the activity of a signal transducer can demonstrate its overall involvement in the transmission of a signal. To further examine its role, it is imperative to more finely pinpoint the in vivo interactions of different areas of the protein with other members of the cascade. To achieve this, we developed a new technique, termed electroporation in situ. Peptides are introduced corresponding to the proteins' points of contact in order to specifically block their interaction. Recent results demonstrated the exquisite ability of this technique to distinguish between closely related signals and open new avenues for the development of peptidomimetic drugs. This apparatus has been used by over a hundred labs worldwide, with results published in Nature, Science, PNAS and other Journals.

This work has been an excellent training ground for a number of graduate students.  Dr Heather Brownell (Ph.D., 1997) was a runner-up for the NSERC doctoral prize and Dr Adina Vultur (Ph.D., 2005) was the recipient of the Governor General's Academic Gold medal as the top graduating Ph.D. student of Queen’s University.  Rozanne Arulanandam (Ph.D. candidate), is on her way to being the next. Several more graduate and 4th year project students had external awards and a large number of publications.

Selected Publications

Geletu M, Hoskin V, Starova B, Niit M, Eliott B, Gunning P.  Differentiation of mouse breast epithelial cells, HC11 and EpH4. Journal of Visualised Experiments, accepted, 2019.

Geletu M, Taha Z, Gunning PT, Raptis L. PI3k and Stat3: Oncogenes that are Required for Gap Junctional, Intercellular Communication. Cancers (Basel). 2019 Feb 1;11(2). pii: E167. doi: 10.3390/cancers11020167. Review.

Niit M, Geletu M, Taha Z, Arulanandam R, Cass J, Hoskin V, Elliott B, Gunning P, Raptis L.   Regulation of Differentiation of HC11 Mouse Breast Epithelial Cells by the Signal Transducer and Activator of Transcription-3. Anticancer Res. 2019 Jun;39(6):2749-2756.

Geletu, M., Taha, Z., Arulanandam, R.,  Mohan, R., Assi, H., Castro, M.G.,  Nabi I. R., Gunning P. T.  and Raptis, L. 2019. Effect of Caveolin-1 upon Stat3 in breast and lung carcinoma cells. Biochemistry and Cell Biology.  15:1-9. doi: 10.1139/bcb-2018-0367.

Geletu M, Mohan R, Arulanandam R, Berger-Becvar A, Nabi IR, Gunning PT, Raptis L.  (2018).  Reciprocal regulation of the Cadherin-11/Stat3 axis by caveolin-1 in mouse fibroblasts and lung carcinoma cells. Biochim Biophys Acta-Molecular Cell Research. 2018 Feb 16. pii: S0167-4889(18)30028-4.

Yetunde Ogunbolude, Chenlu Dai, Edward Bagu, Raghuveera Goel, Sayem Miah, Chi Ying Ng, Rajni Chibbar, Scott Napper, Leda Raptis, Frederick Vizeacoumar, Franco Vizeacoumar, Keith Bonham, and Kiven Lukong.  FRK suppresses the epithelial-mesenchymal transition in breast cancer cells via Stat3/Snail signalling.  Oncotarget, 8(68):113034-113065.

Niit M, Arulanandam R, Cass J, Geletu M, Hoskin V, Côté G, Gunning P, Elliott B, Raptis L. 2017. Regulation of HC11 mouse breast epithelial cell differentiation by the E-cadherin/Rac axis. Experimental Cell Research, 361:112-125.

Mukhopadhyay UK, Cass J, Raptis L, Craig AW, Bourdeau V, Varma S, Gupta SS, Elliott BE, Ferbeyre G.  Dataset of STAT5A status in breast cancer. Data Brief. 2016 Mar 4;7:490-2. doi: 10.1016/j.dib.2016.02.073. eCollection (2016).

Utpal K. Mukhopadhyay, Jamaica Cass, Leda Raptis,  Andrew W. Craig, Véronique Bourdeau, Sonal Varma, Sandip SenGupta, Bruce E. Elliott and Gerardo Ferbeyre. STAT5A is regulated by DNA damage via the tumor suppressor p53.  Cytokine, 82:70-79. doi: 10.1016/j.cyto.2016.01.013

Arulanandam R,   Batenchuk C, Angarita FA,   Ottolino-Perry K,  Cousineau S,  Mottashed A,  Burgess E,  Falls TJ,  De Silva N,   Tsang J,  Howe GA, Bourgeois-Daigneault M-C, Conrad DP,   Daneshmand M, Breitbach CJ,  Kirn DH, Raptis L,   Sad S,  Atkins H,  Huh M,  Diallo J-S,   Lichty, BD,  Ilkow CS,   Le Boeuf F,   Addison CL, McCart JA and Bell JC.   VEGF-Mediated Induction of PRD1-BF1/Blimp1 Expression Sensitizes Tumor Vasculature to Oncolytic Virus Infection.  Cancer Cell, 28:210-24 (2015).

Mulu Geletu,  Stephanie Guy, Samantha Greer and Leda Raptis. Differential effects of polyoma virus middle tumor antigen mutants upon gap junctional, intercellular communication.  Experimental Cell Research, 336:223-231 (2015).

Niit M., Arulanandam R, Geletu M, Hoskin, V., Elliott B and Raptis L. Cell to cell and cell to matrix adhesion in survival and metastasis. Biomolecular concepts, 6:383-399.

Geletu M., Guy S., Firth K. and Raptis L. A functional assay for gap junctional examination; electroporation of adherent cells on Indium-Tin oxide.  Journal of Visualized experiments, (92):e51710.  (1994)

Assi HH, Paran C, Vanderveen N, Savakus J, Doherty R, Petruzzella E, Hoeschele JD, Appelman H, Raptis L, Mikkelsen T, Lowenstein PR, Castro MG. Pre-clinical characterization of signal transducer and activator of transcription 3 small molecule inhibitors for primary and metastatic brain cancer therapy. Journal of  Pharmacology and Experimental Therapeutics.  349:458-69.

Guy S, Geletu M, Arulanandam R, Raptis L. Stat3 and gap junctions in normal and lung cancer cells.  2014.  Cancers (Basel), 6:646-62.

Raptis, L. (2013).  Converting an anarchist-bush area to a garden that does not need watering.  (Μετατρέποντας έναν άναρχο θαμνότοπο σε άνυδρο κήπο).  Agriculture and animal husbandry (Γεωργια και κτηνοτροφια). In Greek.  September, 2013.

Jamaica D Cass, Mulu Geletu, Sandip SenGupta, Bruce E Elliott, Leda Raptis. Activated Stat5 levels do not increase with cell density in contrast to activated Stat3 levels in breast epithelial cell culture. BMC Proceedings 2013, 7(Suppl 2):P31

Geletu M, Guy S, Arulanandam R, Feracci H and Raptis L.  Engaged for survival; from cadherin ligation to Stat3 activation. 2013. JAK-STAT, Volume 2, issue 4 e27363-1 (8 pages).

Carefoot E, Raptis L, Greer P and Elliott BE.   (2013).  The role of Met, Src and Stat3 in basal-like breast cancer invasion.  PMC ID: 3624480. Journal: BMC Proceedings. Publisher: BioMed Central

Geletu M., Guy S. and Raptis L.  Effects of Src and Stat3 upon intercellular communication in lung cancer lines. 2013. Anticancer Research, 33:4401-4410.

Geletu, M., Arulanandam, R., Saez, B., Larue, L., Feracci, H. and Raptis, L. Classical cadherins control survival through the gp130/Stat3 axis. 2013.  BBA-Molecular Cell Research, 1833:1947-1959

Geletu M, Greer S, Arulanandam R,  Tomai, E, Trotman-Grant A, and Raptis, L. Stat3 is a positive regulator of gap junctional communication in cultured, human lung carcinoma cells. BMC cancer, 2012,  2:605 (13 pages).

Jamaica Cass, Sonal Varma, Andrew Day, Waheed Sangrar, Ashish Rajput, Leda Raptis, Jeremy Squire, Yolanda Madarnas, Sandip Sengupta, Bruce Elliott. Automated quantitative analysis of p53, cyclin D1, Ki67 and pERK expression in breast carcinoma does not differ from expert pathologist scoring and correlates with clinico-pathological characteristics. Cancers (Basel) 4:725-742.

Geletu, Mulu, Trotman-Grant, Aaron and Raptis, Leda (2012).  Mind the gap: Regulation of gap  junctional, intercellular communication by the Src oncogene product and its effectors. Anticancer Research, 32:4245-50.

Valiyeva F, Jiang F, Elmaadawi A, Moussa M, Yee SP, Raptis L, Izawa JI, Yang BB, Greenberg NM, Wang F, Xuan JW. (2011). Characterization of the oncogenic activity of the novel TRIM59 gene in mouse cancer models. Mol Cancer Therapeutics, 10:1229-40.

Zhou Z, Hao Y, Liu N, Raptis L, Tsao MS, Yang X. (2011). TAZ is a novel oncogene in non-small cell lung cancer. Oncogene, 30:2181-6.

Raptis, L, Arulanandam, R., Geletu, M. and Turkson, J.  (2011). The R(h)oads to Stat3. Stat3 activation by the Rho GTPases.  Experimental Cell Research, 317:1787-95.

Geletu, M. and Raptis, L. (2011).  Viral oncogenes and the retinoblastoma family.  In: Retinoblastoma, Govindasamy Kumaramanickavel  Editor. InTech, Croatia.  Open access, Book chapter.  Retrieved from http://www.intechweb.org/subject/

Papadakis AI ,  Paraskeva E, Peidis P, Muaddi H, Raptis L, Pantopoulos K , Simos G and Koromilas AE. The eIF2a kinase PKR is implicated in the hypoxic response by acting as a transcriptional suppressor of the HIF1A gene.  Cancer Research, 70:7820-7829.

Mukhopadhyay UK, Mooney P, Jia L, Eves R, Raptis L and Mak AS.  Doubles game:  Src-Stat3 versus p53-PTEN in cellular migration and invasion.   Molecular and Cellular Biology, 30:4980-4995.

Arulanandam, R, Geletu M and Raptis L.  The Simian Virus 40 Large Tumor antigen requires Src for full neoplastic transformation.  Anticancer Research, 30:47-54.

Raptis, L.,  Vultur, A., Brownell, H.L., and Firth, K.L. 2010.  Dissecting pathways; in situ electroporation for the study of signal transduction and gap junctional communication. In: Cell Biology Assays: Essential Methods Geri Kreitzer, Fanny Jaulin, Cedric Espenel Editors. Academic Press Inc., Chapter V, p. 165-183

Raptis L,  Vultur A, Tomai E, Brownell HL and Firth KL 2006. In situ electroporation of radioactive nucleotides: assessment of Ras activity or 32P labelling of cellular proteins. In: Cell Biology Assays: Essential Methods Geri Kreitzer, Fanny Jaulin, Cedric Espenel Editors. Academic Press Inc., Chapter V, p. 183-197

Greer S, Honeywell R,  Geletu M, Arulanandam R and Raptis L.  (2010). Housekeeping genes; expression levels may change with density of cultured cells. Journal of Immunological Methods, 355:76-79. 

Arulanandam, R., Geletu, M.,  Feracci, H. and Raptis, L.  (2010). RacV12 requires gp130 for Stat3 activation, cell proliferation and migration. Experimental Cell Research, 316:875-886.

Arulanandam R, Vultur A, Cao J,  Larue L, Trusdell, P., Carefoot, E., Elliott, BE,  Feracci H and Raptis L. 2009. Cadherin-cadherin engagement promotes survival via Rac/Cdc42 and Stat3.   Molecular Cancer Research, 7:1310-1327.

Raptis, L, Arulanandam, R., Vultur, A., Geletu, M., Chevalier, S. and Feracci, H. 2009. Beyond structure, to survival:  activation of Stat3 by cadherin engagement.  Biochemistry and Cell Biology, 87:835-43.

Geletu, M., Chaize, C., Arulanandam, R., Vultur, A., Kowolik, C., Anagnostopoulou, A., Jove, R. and Raptis, L. Stat3 activity is required for gap junctional permeability in normal epithelial cells and fibroblasts.  DNA and Cell Biology, 28:319-27.

Mohan R, Arulanandam R, Vultur A, Lo O, Cao J and Raptis L. Differential effects of Adenovirus E1A and Simian Virus 40 Large Tumor antigen upon Erk and Akt activity levels in rodent fibroblasts.  Trends in Cell and Molecular Biology, 3:59-68.

Littlefield SL, Baird MC, Anagnostopoulou A  and Raptis L.  2008. Synthesis, characterization and Stat3 inhibitory properties of the prototypical Platinum(IV) Anti-cancer Drug, PtCl3(NO2)(NH3)2 (CPA-7). Inorganic Chemistry, 47: 2798-2804.

Anagnostopoulou A,  Cao J,  Vultur A,  Firth K and Raptis L. (2007) Examination of gap junctional, intercellular communication by in situ electroporation on two co-planar indium-tin oxide electrodes.  Molecular Oncology, 1: 226-231

Raptis L and Firth K. 2008.  Electrode assemblies used for electroporation of cultured cells.  In:  Methods in Molecular Biology. Electroporation protocols.  Shulin Li, ed.  The Humana Press Inc., Totowa, NJ., Chapter 4, pages 58-73.

Raptis L, Vultur A,  Brownell HL, Tomai E, Anagnostopoulou A, Arulanandam R,  Cao J, and  Firth KL. 2008. Electroporation of adherent cells in situ for the study of signal transduction and gap junctional communication. In:  Methods in Molecular Biology. Electroporation protocols.  Shulin Li, ed.  The Humana Press Inc., Totowa, NJ., Chapter 12, pages 167-183.

Cao J,  Arulanandam R,  Vultur A,  Anagnostopoulou A and Raptis L.  2007. Differential effects of c-Ras upon transformation, adipocytic differentiation and apoptosis mediated by the Simian Virus 40 Large Tumor Antigen. Biochemistry and Cell Biology,  85:32-48.

 

Cao J,  Arulanandam R,  Vultur A, Anagnostopoulou A and Raptis L.  2007. Adenovirus E1A requires c-Ras for full neoplastic transformation or suppression of differentiation of murine preadipocytes. Molecular Carcinogenesis, 46:284-302.

Anagnostopoulou A,  Vultur A, Arulanandam R,  Cao J, Turkson J, Jove R,  Joon S. Kim,  Glenn M,  Hamilton AD and Raptis L.  2006.  Role of Stat3 in normal and SV40 transformed cells.  Trends in Cancer Research, 2:93-103.

Raptis, L., Vultur, A., Brownell, H.L., and Firth, K.L. 2006.  Dissecting pathways; in situ electroporation for the study of signal transduction and gap junctional communication. In: Cell Biology, a laboratory Handbook. Third Edition. Celis J, Editor, Academic Press Inc., Volume 2, Chapter 44, pages 341-354.

Raptis L, Vultur A, Tomai E, Brownell HL and Firth KL 2006. In situ electroporation of radioactive nucleotides: assessment of Ras activity or 32P labelling of cellular proteins. In: Cell Biology, a laboratory Handbook. Third Edition. Celis J, Editor, Academic Press Inc., Volume 2, Chapter 43, pages 329-339.

Anagnostopoulou A, Vultur A, Arulanandam R,  Cao J,  Turkson J, Jove R, Joon S. Kim,  Glenn M,  Hamilton AD and  Raptis L.  2006. Differential effects of Stat3 inhibition in sparse vs confluent normal and breast cancer cells.  Cancer Letters, 242:120-132.

Vultur, A.,  Arulanandam, R. Turkson, J.,  Niu, G., Jove, R. and  Raptis, L. (2005).   Stat3 is required for full neoplastic transformation by the Simian Virus 40 Large Tumor antigen. Molecular Biology of the Cell, 16:3832-3846.

Arulanandam, R., Vultur, A. and Raptis, L (2005). Transfection techniques affecting Stat3 activity levels.  Analytical Biochemistry, 338:83-89.

Arulanandam R, Vultur A and Raptis L. 2005. Novel pathway for Stat3 activation. Miami Nature Biotechnology Winter symposia 16:135.

Cao J.,  Arulanandam, R, Vultur, A, Preston, T., Jaronczyk, K., Tomai, E., Zandi, K.  and Raptis, L. (2005).  Differential effects of Adenovirus E1A upon differentiation, transformation and apoptosis  of 3T3L1 preadipocytes.  Molecular Carcinogenesis, 43:38-50.

Vultur, A, Cao, J., Arulanandam, R., Turkson, J., Jove, R., Greer, P., Craig, A., Elliott, B.E. and Raptis, L.  2004. Cell to cell adhesion activates the Stat3 pathway in normal and breast carcinoma cells. Oncogene, 23:2600-2616.

Tomai, E.,  Vultur, A., Balboa, V., Hsu, T., Brownell, H.L., Firth, K.L. and Raptis, L. 2003In situ electroporation of radioactive compounds into adherent cells. DNA and Cell Biology, 22:339-346.

Raptis, L., Balboa, V., Hsu, T., Vultur, A., Turkson, J., Jove, R. and Firth, K.L. (2003). In situ electroporation of large numbers of cells using minimal volumes of material. Analytical Biochemistry, 317:124-8

Vultur, A., Tomai, E., Grammatikakis, N., Forkert, P.G., Malkinson, A.M. and Raptis, L. (2003). Gap junctional, intercellular communication in urethane-induced tumors in A/J mice. DNA and Cell Biology, 20:33-40.

Grammatikakis, N., Vultur, A., Siganou, A., Schweinfest, V., Watson, D. and Raptis, L.. (2002). The role of Hsp90N, a new member of the Hsp90 family, in signal transduction and neoplastic transformation. Journal of Biological Chemistry, 277:8312-8320.

Vultur, A.,  Keiski, C-L.,  Maynard, M., Grammatikakis, N.  and Raptis, L. (2002).  Growth and isotopic labelling of adherent cells in small volumes of medium. Journal of Virology Methods, 101:207-210.

Grammatikakis, N., Jaronczyk, K., Vultur, A., Grammatikakis, A., Brownell, H.L. Benzaquen, M., Rausch, C., Lapointe, R. and Raptis, L. (2001). Simian Virus 40 large Tumor antigen interacts with and modulates the Raf signalling pathway. Journal of Biological Chemistry, 276:27840-27845.

L. Raptis and Vultur, A. 2001. Neoplastic transformation assays. Chapter 11, pages 153-166. In: Methods in Molecular Biology.  SV40 Protocols. Raptis L. ed. The Humana Press Inc., Totowa, NJ.

Brownell, H.L. and Raptis, L.. 2001. [a32P]GTP electroporation for the measurement of Ras activation by SVLT. Chapter 16, pages 221-230. In: Methods in Molecular Biology. SV40 Protocols. Raptis L. ed. The Humana Press Inc., Totowa, NJ.

Tomai, E., Klein, S., Firth, K.L. and Raptis, L. 2000. Growth on Indium-Tin oxide-coated glass enhances 32P-phosphate uptake and protein labelling of adherent cells. Preparative Biochemistry and Biotechnology, 30:313-320.

Raptis, L.,  Firth, K.L. Tomai, E. and Forkert, P.G. 2000. Improved procedure for examination of gap junctional, intercellular communication by in situ electroporation on a partly conductive slide. Biotechniques, 29:222-226.

L. Raptis, H. L. Brownell, A. Vultur, G. Ross, E. Tremblay and B. Elliott. 2000. Specific inhibition of Growth Factor-stimulated ERK1/2 activation in intact cells by electroporation of a Grb2-SH2 binding peptide. Cell Growth and Differentiation, 11:293-303.

Liu, Q-Y, Carson, C., Ribecco, M., Testolin, M., Raptis, L., Walker, P.R. and Sikorska, M. 2000. Effects of neoplastic transformation and Teniposide (VM26) on PKC isoform expression in rodent fibroblasts. Cancer Letters, 153:13-23

Qiao, H., R. Saulnier, A. Patryzkat, N. Rahimi, L. Raptis, J. Rossiter, E. Tremblay, and B. Elliott. 2000. Cooperative effect of Hepatocyte Growth Factor and fibronectin in anchorage‑independent survival of mammary carcinoma cells: Requirement for phosphatidylinositol‑3 kinase activity. Cell Growth and Differentiation, 11:123-133.

Tomai, E., H.L. Brownell, T. Tufescu, K. Reid, B.G. Campling, and L. Raptis. 1999. Gap junctions in lung carcinoma cells. Lung Cancer, 23:223-231.

 Li, G. Szewczuk, M.R., Raptis, L. Johnson, J.G. Weagle, G.E. Pottier, R.H. and Kennedy, J.C. 1999. Rodent fibroblast model for studies of response of malignant cells to exogenous 5-aminolevulinic acid. British Journal of Cancer, 80:676-684.

Tomai, E., H.L. Brownell, T. Tufescu, K. Reid, S. Raptis, B.G. Campling, and L. Raptis. 1998. A functional assay for intercellular, junctional communication in cultured human lung carcinoma cells. Laboratory Investigation, 78:639-640.

Brownell, H.L., N. Lydon, E. Schaefer, T.M. Roberts, and L. Raptis. 1998. Inhibition of Epidermal Growth Factor‑mediated ERK1/2 activation by in situ electroporation of nonpermeant [(alkylamino)methyl]acrylophenone derivatives. DNA and Cell Biology, 17:265-274. 

Raptis, L., H.L. Brownell, N.B. Lydon, and T.M. Roberts. 1998. Inhibition of EGF‑induced ERK1 and ERK2 enzyme activation in NIH3T3 cells by in situ electroporation of a nonpermeant inhibitor. Promega Notes 67:12‑15.

Raptis, L., H.L. Brownell, K.L. Firth and S. Giorgetti-Peraldi. 1998. In situ electroporation for the study of signal transduction, J.C. Celis (ed.), Cell Biology: A laboratory handbook. Academic Press Inc., Volume 4:75-87.

Brownell, H.L. and Raptis, L.. 1998. Electroporation of nucleotides. Assessment of Ras activity. 32P‑labelling of cellular components, J.C. Celis (ed.), Cell Biology: A laboratory handbook. Academic Press Inc., Volume 4:65-74.

Brownell, H.L., S. Giorgetti‑Peraldi, E. Tomai, K.L. Firth, and L. Raptis. 1998. In situ electroporation in the study of signal transduction, G.G. Skouteris and G.L. Nickolson (eds.), Intermolecular cross‑talk in tumor metastasis. IOS Press, Netherlands.

Raptis, L., H.L. Brownell, Y. Lu, T. Preston, R.P. Narsimhan, E. Schaefer, S. Anderson, and T. Haliotis. 1997. v‑Ras and v‑Raf block differentiation of transformable C3H10T½‑derived preadipocytes at lower levels than required for neoplastic transformation. Experimental Cell Res., 235:188-197.

Firth, K.L., H.L. Brownell, and L. Raptis. 1997. An improved procedure for electroporation of peptides into adherent cells in situ. Biotechniques, 23:644-645.

Brownell, H.L., J.F. Whitfield, and L. Raptis. 1997. Elimination of intercellular junctional communication requires lower Rasleu61 levels than stimulation of anchorage‑independent proliferation. Cancer Detect. Prev. 21:289‑294.

Raptis, L., H.L. Brownell, K. Wood, M. Corbley, D. Wang, and T. Haliotis. 1997. Cellular ras gene activity is required for full neoplastic transformation by Simian Virus 40. Cell Growth and Differentiation. 8:891‑901

Preston, T., H.L. Brownell, and L. Raptis. 1997. The timing of insulin/c‑Ras signal is critical for its effect upon the differentiation of 10T½‑derived preadipocytes. Cancer Lett. 115:165‑171.

 Raptis, L., J. Yang, H.L. Brownell, J. Lai, T. Preston, M.J. Corbley, R.P. Narsimhan, and T. Haliotis. 1997. Rasleu61 blocks differentiation of transformable 3T3 L1 and C3H10T½‑derived preadipocytes in a dose‑ and time‑dependent manner. Cell Growth and Differentiation 8:11‑21.

Brownell, H.L., K.L. Firth, K. Kawauchi, T.L. Delovitch, and L. Raptis. 1997. A novel technique for the study of Ras activation; electroporation of [α32P]GTP. DNA and Cell Biology 16:103‑110.

Royal, I., L. Raptis, B.J. Druker, and N. Marceau. 1996. Downregulation of cytokeratin 14 gene expression by the polyoma virus middle-T antigen is dependent on c-src association but independent of full transformation in rat liver nonparenchymal epithelial cells. Cell Growth and Differentiation, 7:737-743.

 Brownell, H.L., J.F. Whitfield, and Raptis, L. 1996. Cellular Ras partly mediates gap junction closure by the polyoma virus middle Tumor antigen. Cancer Letters, 103:99-106.

Brownell, H.L., Narsimhan, R.P., Corbley, M.J., Mann, V.M., Whitfield, J.J. and Raptis, L. 1996. Ras is involved in gap junction closure in fibroblasts or preadipocytes but not differentiated adipocytes. DNA and Cell Biology, 15:443-451.

Raptis, L., K.L. Firth, H.L. Brownell, A. Todd, W.C. Simon, B.M. Bennett, and M. Zannis‑Hadjopoulos. 1995. Electroporation of adherent cells in situ for the introduction of nonpermeant molecules, J.A. Nickoloff (ed.), Methods in Molecular Biology. Protocols for electroporation and electrofusion of Plant and Animal Cells. The Humana Press Inc., Totowa, NJ., Chapter 7:93-113 (invited review).

Raptis, L., Liu, S.K.W., Firth, K.L., Stiles C.D. and Alberta, J.A. 1995. Electroporation of peptides into adherent mammalian cells in situ. Biotechniques, 18:104-114.

Raptis, L., H.L. Brownell, Liu, S.K.W., K.L. Firth, and L.W. MacKenzie. 1995. Applications of electroporation of adherent cells in situ, on a partly conductive slide. Molecular Biotechnology, 4:129-138.

Raptis, L., H.L. Brownell, K.L. Firth, and L.W. MacKenzie. 1994. A novel technique for the study of intercellular, junctional communication; electroporation of adherent cells on a partly conductive slide. DNA and Cell Biology, 13:963-975.

Raptis, L., Marcellus, R.C. and Whitfield, J.F. 1993. High membrane-associated Protein Kinase C activity correlates to tumorigenicity but not anchorage-independence in a clone of mouse NIH 3T3 cells. Experimental Cell Research 207:152‑154.

Simon, W.C., Raptis, L., Pang, S.C. and Bennett, B.M. 1993. Comparison of liposome fusion and electroporation for the intracellular delivery of nonpermeant molecules to cultured, adherent cells. Journal of Pharmacological and Toxicological Methods, 29:29-35.

Lu, Y., L. Raptis, S. Anderson, M.J. Corbley, Y.‑C. Zhou, H. Pross, and T. Haliotis, T. 1992. p21ras modulates commitment and maturation of 10T½ fibroblasts to adipocytes. 25th Anniversary issue, Biochemistry and Cell Biology, 70:1249-1257

Raptis, L., Marcellus, R.C., Corbley, M., Krook, A., Whitfield, J.F., Anderson, S. and Haliotis, T. 1991. Cellular ras gene activity is required for transformation by polyoma virus. Journal of Virology, 65:5203‑5210.

Marcellus, R.C., Whitfield J.F. and Raptis, L. 1991. Polyoma virus middle tumor antigen stimulates membrane‑associated protein kinase C at lower levels than required for phosphatidylinositol kinase activation and neoplastic transformation. Oncogene, 6:1037‑1040.

Raptis, L. 1991. Polyoma virus middle Tumor antigen increases the responsiveness to growth factors. Journal of Virology, 65:2691‑2694.

Raptis, L., Marcellus, R.C. and Whitfield, J.F. 1990. Transforming signals generated by the polyoma virus tumor antigens. Advances in Enzyme Regulation 30:133‑142.

Raptis, L. and Firth, K. L. 1990. Electroporation of adherent cells in situ. DNA and Cell Biology 9:615‑621.

Raptis, L. and Bolen, J.B. 1989. Polyoma virus transforms rat F111 and mouse NIH3T3 cells by different mechanisms. Journal of Virology 63:753‑758.

Raptis, L. Whitfield, J. F. and Bell, J. 1988. Protein kinase C increases the activity of the polyoma virus middle T antigen‑associated phosphatidylinositol kinase. Biochem. Biophys. Res. Comm. 154:306‑311.

Whitfield, J.F., Durkin, J.P., Franks, D.J., Kleine, L.P., Raptis, L., Rixon, R.H., Sikorska, M. and Walker, P.R. 1987. Calcium, cyclic AMP and protein kinase C ‑ partners in mitogenesis. Cancer and Metastasis Reviews, Fidler and Poste, eds., Martinus Nijhoff, Boston. Vol.5, pp.205‑250.

Raptis, L. and Whitfield, J.F. 1986. Protein kinase C increases the transforming ability of the polyoma virus middle T antigen. Biochem. Biophys. Res. Comm. 140:1106‑1112.

Raptis, L., Boynton, A.L. and Whitfield, J.F. 1986. Protein kinase C promotes the phosphorylation of immunoprecipitated middle T antigen from polyoma‑transformed cells. Biochem. Biophys. Res. Comm. 136:995‑1000.

Boynton, A.L., Whitfield, J.F., Bossi, D., Durkin, J.P., Franks, D., Kleine, L.P. and Raptis, L. 1986. Protein kinase C, calcium, cAMP and their role in cell proliferation and oncogenesis. In: Membranes in tumor growth. Galeotti et al., eds., Elsevier, North Holland.

Kaplan, D., Whitman, M., Raptis, L., Garcea, B., Schaffhausen, B., Roberts, T. and Cantley, L. 1986. Phosphatidylinositol metabolism and polyoma‑mediated transformation. Proc. Nat. Acad. Sci. USA 83:3624‑3628.

Raptis, L., Lamfrom, H. and Benjamin, T.L. 1985. Regulation of cellular phenotype and expression of polyoma virus middle T antigen in rat fibroblasts. Molecular and Cellular Biology 5:1476‑1485.

Hannan, C., Raptis, L., Dery, C. and Weber J. 1983. Biological and structural studies with an Adenovirus type 2 mutant defective for uncoating. Intervirology 19:213‑223.

Raptis, L., Comlan de Souza, A., M'Bikay, M., Thirion, J.P. and Weber, J. 1982. Stable integration of Adenovirus DNA is not required for the induction of mutations in the hypoxanthine phosphoribosyl transferase gene in Chinese hamster cells. Mutation Research 105:371‑375.

Baumann, E.A., Stedtman, D., Raptis, L., Fuks, A. and Hand, R. 1981. Immunological cross‑reactivity between SV40 large T antigen and D2 hybrid T antigen. J. of Virology. 38:1090‑1094.

Raptis, L. and Bourgaux, P. 1981. Two classes of replicating molecules of Adenovirus type 2 DNA. Biochim. Biophys. Acta. 652:331‑343.

Raptis, L. and Menard, H.A. 1980. Quantitation and characterization of plasma DNA in normals and patients with Systemic Lupus Erythematosus. Journal of Clinical Investigation. 66:1391‑1399.

Menard, H.A. and Raptis, L. 1979. Absence d'anticorps anti‑ADN natif au cours de l'hepatite chronique active. La nouvelle presse médicale 8(48):3973.

Couture, F., Beaulieu, A., Raptis, L. and Menard, H.A. 1979. Operationally defined single‑ and double‑stranded DNA antigens in the Farr assay: diagnostic value. Eur. J. of Clin. Invest. 9:243‑251.

Raptis, L., Delbecchi, L. and Bourgaux, P. 1978. Further studies on the replication of Adenovirus‑2 DNA. Can. J. Biochemistry 56(9):857‑865.