Javier Pizarro

Mismatch repair gene expression and genetic instability in testicular germ cell tumor

Human mismatch repair (MMR) genes encode highly conserved interacting proteins that correct replication errors predisposing to hereditary gastrointestinal and genitourinary malignancies. A subset of sporadic genitourinary tumors also exhibits MMR deficiency and can be identified by measuring the frequency of microsatellite instability (MSI) in cancer cell DNA. We investigated the expression of the two most commonly mutated MMR genes, MSH2 and MLH1 in sporadic testicular germ cell tumor (GCT) in order to: 1) determine the expression pattern of MSH2 and MLH1 proteins in normal seminiferous tubules and histologically distinct GCT subtypes, 2) correlate MMR gene expression with genetic instability in GCT and 3) develop a panel of molecular markers that can identify genetically distinct subsets of GCT for prognostic assessment. MSH2 and MLH1 had differential staining patterns in normal seminiferous tubules and malignant tissues. MSH2 was expressed in all stages of spermatogenesis up to but excluding mature sperm whereas MLH1 was predominantly expressed in premeiotic germ cells. All histological GCT subtypes showed differential immunostaining for MSH2 and MLH1 however pure seminoma had statistically significant fewer low MSH2 staining tumors than other subtypes (p=0.046). Twenty-five percent of GCT exhibited increased frequency of MSI (MSI+ tumors) with 73, 70 and 43% of MSI+ tumors exhibiting low MSH2, low MLH1 or low MSH2 and low MLH1 staining respectively. Fifteen percent of testicular GCT exhibited loss of heterozygosity (LOH) but no MSI (LOH only tumors). Only 28, 17 or 6% of LOH only tumors exhibited low MSH2, low MLH1 or low MSH2 and low MLH1 staining respectively.

Metformin, at Concentrations Corresponding to the Treatment of Diabetes, Potentiates the Cytotoxic Effects of Carboplatin in Cultures of Ovarian Cancer Cells

The use of the type 2 diabetics drug metformin has been correlated with enhanced progression-free survival in ovarian cancer. The literature has speculated that this enhancement is due to the high concentration of metformin directly causing cancer cell death. However, this explanation does not fit with clinical data reporting that the women exposed to constant micromolar concentrations of metformin, as present in the treatment of diabetes, respond better to chemotherapy. Herein, our aim was to examine whether micromolar concentrations of metformin alone could bring about cancer cell death and whether micromolar metformin could increase the cytotoxic effect of commonly used chemotherapies in A2780 and SKOV3 cell lines and primary cultured cancer cells isolated from the peritoneal fluid of patients with advanced ovarian cancer. Our results in cell lines demonstrate that no significant loss of viability or change in cell cycle was observed with micromolar metformin alone; however, we observed cytotoxicity with micromolar metformin in combination with chemotherapy at concentrations where the chemotherapy alone produced no loss in viability. We demonstrate that previous exposure and maintenance of metformin in conjunction with carboplatin produces a synergistic enhancement in cytotoxicity of A2780 and SKOV3 cells (55% and 43%, respectively). Furthermore, in 5 (44%) of the 11 ovarian cancer primary cultures, micromolar metformin improved the cytotoxic response to carboplatin but not paclitaxel or doxorubicin. In conclusion, we present data that support the need for a clinical study to evaluate the adjuvant maintenance or prescription of currently approved doses of metformin during the chemotherapeutic treatment of ovarian cancer.

Potencial herramienta en la personalización del tratamiento oncológico: Casos clínicos

Our laboratory has implemented an in vitro assay to estimate the response to chemotherapy in ovarian cancer cells pertaining to individual patients. In two selected patients, we determined the correlation between an in vitro assay of cells from suspected ovarian cancer ascites, with the clinical chemotherapy response. Cancer cells isolated from peritoneal fluid with suspected ovarian cancer were tested for cytotoxicity with corresponding chemotherapy regimens. Circulating Cal25 levels and attending physician consultation determined clinical course and response to chemotherapy. The in vitro assay result correlated with Cal25 levels, progression free survival and attending physician evaluation. The assay predicted correctly the failure of two successive chemotherapy regimes in the first patient, while predicting a favorable clinical response in the second subject.