Correlation between ERK1 and STAT3 expression and chemoresistance in patients with conventional osteosarcoma

Background

The standard therapy regimen of conventional osteosarcoma includes neoadjuvant chemotherapy followed by surgical resection and postoperative chemotherapy. The percentage of necrotic tissue following induction chemotherapy is assessed by using the Huvos grading system, which classifies patients as “poor responders” (PR) and “good responders” (GR). The aim of this study was to identify molecular markers expressed differentially between good and poor responders to neoadjuvant chemotherapy in order to predict the response to chemotherapy in conventional osteosarcomas before beginning treatment.

Methods

Suppression Substractive Hybridization (SSH) was performed by using cDNA from frozen biopsy specimens. Expression of selected relevant genes identified by SSH was validated by using QRT-PCR. Immunohistochemistry (IHC) on tissue microarray (TMA) sections of 52 biopsies was performed to investigate protein expression in an independent cohort.

Results

ERK1 and STAT3 mRNA level were significantly different between PR and GR in an independent cohort. Phosphorylated STAT3 and ERK1 expressions by IHC on TMA were correlated with poor response to chemotherapy.

Conclusions

Our results suggest that ERK1 and STAT3 expression are good predictive markers for chemotherapy response and that inhibitors might be used in combination with common chemotherapeutic drugs in conventional osteosarcomas.

Direct identification of Photobacterium damselae subspecies piscicida by PCR-RFLP analysis

Fish pasteurellosis is an infectious disease that affects several teleost species living in temperate marine waters. The pathogen responsible, Photobacterium damselae subspecies piscicida, shows high genetic similarity with P. damselae subsp. damselae, making subspecies discrimination extremely laborious. Here we report for the first time a PCR-RFLP method for the identification of P. damselae subsp. piscicida without prior isolation in pure culture. Genomic sequence information was obtained through cloning and sequencing of RAPD products. Two P. damselae-specific primer pairs were developed and tested on 17 strains of P. damselae subsp. piscicida, 10 strains of P. damselae subsp. damselae, and 6 closely related control species. High sensitivity was achieved in PCR amplification on serially diluted samples (<180 fg of pure bacterial DNA or <10 fg, depending on the amplified fragment). Restriction analysis of PCR products showed a unique digestion profile for all P. damselae subsp. piscicida strains. The same PCR-RFLP method was implemented on total DNA samples extracted from experimentally infected sea bream and sea bass. Positive results were obtained on fish with clear signs of the disease as well as on challenged, but asymptomatic, fish. The method presented here might provide a useful tool for both prevention and rapid diagnosis of fish pasteurellosis.