Sub-additive effects of photodynamic therapy combined with erlotinib for the treatment of epidermoid carcinoma: An in vitro study.
BACKGROUND
Photodynamic therapy (PDT) is an antitumour treatment that employs the combination of a photosensitive compound, oxygen and visible light. To improve the antitumour activity of PDT, the present study used the strategy of combining PDT with erlotinib (ERL), a drug frequently used in the treatment of epidermoid carcinoma.


METHODS
An MTT cell viability assay was used to evaluate the cytotoxicity of PDT combined with ERL on A431 epidermoid carcinoma cells in vitro. This study evaluated the cytotoxicity of the following treatments: red laser irradiation (660nm) at different power densities (1.25-180J/cm2), the photosensitizer methylene blue (MB) at concentrations of 0.39-100μM, PDT (12.5μM MB and laser power densities from 1.25 to 180J/cm2), and PDT (12.5μM MB and a laser density of 120J/cm2) plus ERL (1μM).


RESULTS
The laser power densities that were tested showed no cytotoxicity in A431 cells. MB showed a dose-dependent cytotoxicity. In PDT, an increase in the dose of light resulted in an increase in the cytotoxicity of MB. In addition, there was a sub-additive effect between PDT and ERL compared to the effect of each therapy alone.


CONCLUSIONS
The sub-additive effect between PDT and ERL suggests that their combination may be an important strategy in the treatment of epidermoid carcinoma.
Restorative Dentistry Department, Faculty of Dentistry, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Sávio M L
SML
Gontijo
Restorative Dentistry Department, Faculty of Dentistry, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Renata C
RC
Felizali
Chemistry Department, Institute of Exact Sciences, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Pedro P G
PPG
Guimarães
Department of Physiology and Biophysics, Institute of Biological Sciences, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Robson A S
RAS
Santos
Chemistry Department, Institute of Exact Sciences, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Rubén D
RD
Sinisterra
Restorative Dentistry Department, Faculty of Dentistry, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil.
Maria E
ME
Cortés
Restorative Dentistry Department, Faculty of Dentistry, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, CEP 31270-901 Belo Horizonte, MG, Brazil. Electronic address: patriciavalenteufmg@gmail.com.
Patrícia V
PV
Araújo
D000970:Antineoplastic Agents / Q000008:administration & dosage; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D059248:Chemoradiotherapy / Q000379:methods*; D003131:Combined Modality Therapy / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D000069347:Erlotinib Hydrochloride / Q000008:administration & dosage*; D006801:Humans; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000008:administration & dosage; D011829:Radiation Dosage; D016896:Treatment Outcome
D000970:Antineoplastic Agents; D017319:Photosensitizing Agents; D000069347:Erlotinib Hydrochloride
A431 epidermoid carcinoma; Erlotinib; Methylene blue; Photodynamic therapy