Overexpression of caspase-3s splice variant in locally advanced breast carcinoma is associated with poor response to neoadjuvant chemotherapy.
OBJECTIVE
CASP-3 gene gives rise, by alternative splicing to a caspase-3s variant, to the antagonist apoptotic property of caspase-3. Deregulation of splicing in tumor cells favoring the expression of antiapoptotic variants has been reported to contribute to both tumorigenesis and chemoresistance. Thus, we investigated the role of caspase-3 and its splice variant in breast cancer cells.


METHODS
Breast tumor cell lines deficient (MCF-7) and proficient (HBL100) for CASP-3 gene were transfected with each transcript and were characterized for their apoptotic response to cyclophosphamide. Expression of the two transcripts were measured by reverse transcription-PCR in 130 breast carcinomas, including 90 locally advanced tumors treated with neoadjuvant chemotherapy containing cyclophosphamide, epirubicine, and 5-fluorouracil.


RESULTS
Overexpression of caspase-3s variant in caspase-3-transfected cell lines significantly inhibits apoptosis induced by cyclophosphamide (P < 0.0001 for both cell lines). In breast tissues, only caspase-3 levels were higher in carcinomas than in corresponding adjacent normal tissues (P = 0.0396). Locally advanced carcinomas with high levels of caspase-3 (P < 0.0001) and weak levels of caspase-3s (P = 0.0248) were more sensitive to treatment. Therefore, increase in caspase-3s/caspase3 ratio expression was significantly associated with chemoresistance (P = 0.01). Logistic univariate and multivariate analyses realized according to pathologic response confirm that increased caspase-3s expression was indicative of chemoresistance (P = 0.012 and P = 0.026, respectively).


CONCLUSIONS
The results agree with an antagonist function between the two transcripts of caspase-3 and show that their ratio of expression levels may define a subset of locally advanced breast cancer patients who are more likely to benefit from neoadjuvant cyclophosphamide-containing chemotherapy.
Végran
Frédérique
F
Laboratory of Molecular Genetics, Institut National de la Sante et de la Recherche Medicale U-517, Centre Georges François Leclerc, 1 rue du professeur Marion, 21034 Dijon cedex, France.
Boidot
Romain
R
Oudin
Claire
C
Riedinger
Jean-Marc
JM
Bonnetain
Franck
F
Lizard-Nacol
Sarab
S
D017398:Alternative Splicing; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000235:genetics*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D018270:Carcinoma, Ductal, Breast / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000235:genetics* / Q000378:metabolism; D017024:Chemotherapy, Adjuvant; D003520:Cyclophosphamide / Q000627:therapeutic use; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004792:Enzyme Precursors; D015251:Epirubicin / Q000627:therapeutic use; D005260:Female; D005472:Fluorouracil / Q000627:therapeutic use; D005786:Gene Expression Regulation; D006801:Humans; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D014407:Tumor Cells, Cultured
D061945:Caspase Inhibitors; D004792:Enzyme Precursors; D015251:Epirubicin; D003520:Cyclophosphamide; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D005472:Fluorouracil