FUNCTIONAL IN VITRO ANALYSES OF LIPID RAFT-ASSOCIATED CATHEPSIN B: IMPLICATION FOR THE INVASIVE PHENOTYPE
OF INFLAMMATORY BREAST CANCER
by
BERNADETTE C. VICTOR
December 2011
Advisor: Dr. Bonnie F. Sloane
Major: Cancer Biology
Degree: Doctor of Philosophy
Inflammatory breast cancer (IBC) is an aggressive, metastatic and
highly angiogenic form of locally advanced breast cancer. Breast
cancer invasion has been linked to proteolytic activity at the tumor
cell surface. We observed that uPA, uPAR and enzymatically active
cathepsin B were all present in caveolae fractions isolated from
SUM149 cells. Using a live-cell proteolysis assay, we demonstrated
that both IBC cell lines degrade type IV collagen. The SUM149 cells
exhibit predominantly pericellular proteolysis, consistent with
localization of constituents of a proteolytic pathway to membrane
microdomains. A functional role for cathepsin B was confirmed by
the ability of CA074, a cell impermeable and highly selective
cathepsin B inhibitor, to significantly reduce pericellular proteolysis
and invasion by SUM149 cells. A statistically significant co-
expression of cathepsin B and caveolin-1 was found in IBC patient
biopsies, thus validating our in vitro data. To determine whether the
uPA and cathepsin B present at the cell surface is localized
specifically to caveolae and investigate if caveolae are a functional
component of the IBC phenotype, we knocked down the expression
of caveolin-1 in SUM149 cells. The subcellular distribution of
cathepsin B was unchanged in caveolin-1 knockdown SUM149 cells.
In contrast, knockdown decreased the association of both uPA and
EGFR with caveolae. Knockdown of caveolin-1 also decreased
degradation of type IV collagen and invasion by IBC cells. We also
determined that targeted disruption of lipid microdomains by use of
lovastatin diminished the aggressiveness of IBC cells. Cathepsin B
activity and association with lipid microdomains was reduced in
lovastatin treated IBC cells. Lovastatin treatment also reduced type
IV collagen degradation and invasion by IBC cells. In conclusion, we
have shown that cathepsin B and caveolin-1 both contribute to the
aggressiveness of IBC, albeit by different mechanisms.
","abstract_html":"<p>FUNCTIONAL IN VITRO ANALYSES OF LIPID RAFT-ASSOCIATED CATHEPSIN B: IMPLICATION FOR THE INVASIVE PHENOTYPE </p> <p>OF INFLAMMATORY BREAST CANCER</p> <p>by</p> <p>BERNADETTE C. VICTOR</p> <p>December 2011</p> <p>Advisor: Dr. Bonnie F. Sloane</p> <p>Major: Cancer Biology </p> <p>Degree: Doctor of Philosophy</p> <p>Inflammatory breast cancer (IBC) is an aggressive, metastatic and </p> <p>highly angiogenic form of locally advanced breast cancer. Breast </p> <p>cancer invasion has been linked to proteolytic activity at the tumor </p> <p>cell surface. We observed that uPA, uPAR and enzymatically active </p> <p>cathepsin B were all present in caveolae fractions isolated from </p> <p>SUM149 cells. Using a live-cell proteolysis assay, we demonstrated </p> <p>that both IBC cell lines degrade type IV collagen. The SUM149 cells </p> <p>exhibit predominantly pericellular proteolysis, consistent with </p> <p>localization of constituents of a proteolytic pathway to membrane </p> <p>microdomains. A functional role for cathepsin B was confirmed by </p> <p>the ability of CA074, a cell impermeable and highly selective </p> <p>cathepsin B inhibitor, to significantly reduce pericellular proteolysis </p> <p>and invasion by SUM149 cells. A statistically significant co-</p> <p>expression of cathepsin B and caveolin-1 was found in IBC patient </p> <p>biopsies, thus validating our in vitro data. To determine whether the </p> <p>uPA and cathepsin B present at the cell surface is localized </p> <p>specifically to caveolae and investigate if caveolae are a functional </p> <p>component of the IBC phenotype, we knocked down the expression </p> <p>of caveolin-1 in SUM149 cells. The subcellular distribution of </p> <p>cathepsin B was unchanged in caveolin-1 knockdown SUM149 cells. </p> <p>In contrast, knockdown decreased the association of both uPA and </p> <p>EGFR with caveolae. Knockdown of caveolin-1 also decreased </p> <p>degradation of type IV collagen and invasion by IBC cells. We also </p> <p>determined that targeted disruption of lipid microdomains by use of </p> <p>lovastatin diminished the aggressiveness of IBC cells. Cathepsin B </p> <p>activity and association with lipid microdomains was reduced in </p> <p>lovastatin treated IBC cells. Lovastatin treatment also reduced type </p> <p>IV collagen degradation and invasion by IBC cells. In conclusion, we </p> <p>have shown that cathepsin B and caveolin-1 both contribute to the </p> <p>aggressiveness of IBC, albeit by different mechanisms.</p>","abstract_has_math":false,"creators":["Victor, Bernadette Caroline"],"institution":null,"degree_name":"Ph.D.","degree_level":"Open Access Dissertation","degree_discipline":"Cancer Biology","degree_department":null,"school":null,"contributors":["Bonnie F. Sloane"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-01-01T08:00:00Z","date_published":"2011-01-01T08:00:00Z","updated_at":"2026-07-24T05:58:57Z","subjects":["cathepsin B, caveolae, inflammatory breast cancer, invasion, proteolysis","Cell Biology"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://digitalcommons.wayne.edu/oa_dissertations/400","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Bonnie F. Sloane"]},{"key":"dc:creator","label":"Author","values":["Victor, Bernadette Caroline"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2011-01-01T08:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Cancer Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Open Access Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["cathepsin B, caveolae, inflammatory breast cancer, invasion, proteolysis","Cell Biology"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://digitalcommons.wayne.edu/oa_dissertations/400"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["FUNCTIONAL IN VITRO ANALYSES OF LIPID RAFT-ASSOCIATED CATHEPSIN B: IMPLICATION FOR THE INVASIVE PHENOTYPE
OF INFLAMMATORY BREAST CANCER
by
BERNADETTE C. VICTOR
December 2011
Advisor: Dr. Bonnie F. Sloane
Major: Cancer Biology
Degree: Doctor of Philosophy
Inflammatory breast cancer (IBC) is an aggressive, metastatic and
highly angiogenic form of locally advanced breast cancer. Breast
cancer invasion has been linked to proteolytic activity at the tumor
cell surface. We observed that uPA, uPAR and enzymatically active
cathepsin B were all present in caveolae fractions isolated from
SUM149 cells. Using a live-cell proteolysis assay, we demonstrated
that both IBC cell lines degrade type IV collagen. The SUM149 cells
exhibit predominantly pericellular proteolysis, consistent with
localization of constituents of a proteolytic pathway to membrane
microdomains. A functional role for cathepsin B was confirmed by
the ability of CA074, a cell impermeable and highly selective
cathepsin B inhibitor, to significantly reduce pericellular proteolysis
and invasion by SUM149 cells. A statistically significant co-
expression of cathepsin B and caveolin-1 was found in IBC patient
biopsies, thus validating our in vitro data. To determine whether the
uPA and cathepsin B present at the cell surface is localized
specifically to caveolae and investigate if caveolae are a functional
component of the IBC phenotype, we knocked down the expression
of caveolin-1 in SUM149 cells. The subcellular distribution of
cathepsin B was unchanged in caveolin-1 knockdown SUM149 cells.
In contrast, knockdown decreased the association of both uPA and
EGFR with caveolae. Knockdown of caveolin-1 also decreased
degradation of type IV collagen and invasion by IBC cells. We also
determined that targeted disruption of lipid microdomains by use of
lovastatin diminished the aggressiveness of IBC cells. Cathepsin B
activity and association with lipid microdomains was reduced in
lovastatin treated IBC cells. Lovastatin treatment also reduced type
IV collagen degradation and invasion by IBC cells. In conclusion, we
have shown that cathepsin B and caveolin-1 both contribute to the
aggressiveness of IBC, albeit by different mechanisms.
"]},{"key":"dc:title","label":"Title","values":["Functional in vitro analyses of lipid raft-associated cathepsin b: implication for the invasive phenotype of inflammatory breast cancer"]}]}],"canonical_facts":{"dc:contributor":["Bonnie F. Sloane"],"dc:creator":["Victor, Bernadette Caroline"],"dc:date.available":["2011-01-01T08:00:00Z"],"dc:description.abstract":["FUNCTIONAL IN VITRO ANALYSES OF LIPID RAFT-ASSOCIATED CATHEPSIN B: IMPLICATION FOR THE INVASIVE PHENOTYPE
OF INFLAMMATORY BREAST CANCER
by
BERNADETTE C. VICTOR
December 2011
Advisor: Dr. Bonnie F. Sloane
Major: Cancer Biology
Degree: Doctor of Philosophy
Inflammatory breast cancer (IBC) is an aggressive, metastatic and
highly angiogenic form of locally advanced breast cancer. Breast
cancer invasion has been linked to proteolytic activity at the tumor
cell surface. We observed that uPA, uPAR and enzymatically active
cathepsin B were all present in caveolae fractions isolated from
SUM149 cells. Using a live-cell proteolysis assay, we demonstrated
that both IBC cell lines degrade type IV collagen. The SUM149 cells
exhibit predominantly pericellular proteolysis, consistent with
localization of constituents of a proteolytic pathway to membrane
microdomains. A functional role for cathepsin B was confirmed by
the ability of CA074, a cell impermeable and highly selective
cathepsin B inhibitor, to significantly reduce pericellular proteolysis
and invasion by SUM149 cells. A statistically significant co-
expression of cathepsin B and caveolin-1 was found in IBC patient
biopsies, thus validating our in vitro data. To determine whether the
uPA and cathepsin B present at the cell surface is localized
specifically to caveolae and investigate if caveolae are a functional
component of the IBC phenotype, we knocked down the expression
of caveolin-1 in SUM149 cells. The subcellular distribution of
cathepsin B was unchanged in caveolin-1 knockdown SUM149 cells.
In contrast, knockdown decreased the association of both uPA and
EGFR with caveolae. Knockdown of caveolin-1 also decreased
degradation of type IV collagen and invasion by IBC cells. We also
determined that targeted disruption of lipid microdomains by use of
lovastatin diminished the aggressiveness of IBC cells. Cathepsin B
activity and association with lipid microdomains was reduced in
lovastatin treated IBC cells. Lovastatin treatment also reduced type
IV collagen degradation and invasion by IBC cells. In conclusion, we
have shown that cathepsin B and caveolin-1 both contribute to the
aggressiveness of IBC, albeit by different mechanisms.
"],"dc:identifier":["https://digitalcommons.wayne.edu/oa_dissertations/400"],"dc:subject":["cathepsin B, caveolae, inflammatory breast cancer, invasion, proteolysis","Cell Biology"],"dc:title":["Functional in vitro analyses of lipid raft-associated cathepsin b: implication for the invasive phenotype of inflammatory breast cancer"],"thesis:degree_discipline":["Cancer Biology"],"thesis:degree_level":["Open Access Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-24T05:58:57Z"}