Faculty Bibliography

Previous studies have shown that pharmacologic inhibition of poly (ADP-ribose) polymerase (PARP), a nuclear protein that is crucial in signaling single-strand DNA breaks, is synthetically lethal to cancer cells from patients with genetic deficiency in the DNA repair proteins BRCA1 and BRCA2. Herein, we demonstrate that depletion of the mitochondrial genome (mtDNA) in breast, prostate and thyroid transformed cells resulted in elevated steady-state cytosolic calcium concentration and activation of calcineurin/PI3-kinase/AKT signaling leading to upregulation of miR-1245 and the ubiquitin ligase Skp2, two potent negative regulators of the tumor suppressor protein BRCA2, thus resulting in BRCA2 protein depletion, severe reduction in homologous recombination (HR) and increased sensitivity to the PARP inhibitor rucaparib. Treatment of mtDNA-depleted cells with the PI3-kinase inhibitor LY294002, the calmodulin antagonist W-7, the calcineurin inhibitor FK506, the calcium chelator BAPTA-AM, or suppression of AKT activity by AKT small-interfering RNA (siRNA) enhanced BRCA2 protein levels as well as HR. Decreasing the intracellular calcium levels using BAPTA, or direct reconstitution of BRCA2 protein levels either by recombinant expression or by small molecule inhibition of both Skp2 and miR-1245 restored sensitivity to rucaparib to wild-type levels. Furthermore, by studying prostate tissue specimens from prostate carcinoma patients we found a direct correlation between the presence of mtDNA large deletions and loss of BRCA2 protein in vivo, suggesting that mtDNA status may serve as a marker to predict therapeutic efficacy to PARP inhibitors. In summary, our results uncover a novel mechanism by which mtDNA depletion restrains HR, and highlight the role of mtDNA in regulating sensitivity to PARP inhibitors in transformed cells.

In addition to their role as cell powerhouse mitochondria are key organelles in the processes deciding about cell life or death that are crucial for tumor cell growth and survival, as well as for tumor cell ability to metastasize. Alterations in mitochondrial structure and functions have long been observed in cancer cells, thus targeting mitochondria as an anticancer therapeutic strategy has gained momentum recently. We will review the achievements and perspectives in the elucidation of the molecular basis for developing mitochondrial-targeted compounds as potential anticancer agents with special attention to mitochondrial DNA mutations and mitochondrial dysfunction. Molecules/agents candidate to affect mitochondrial metabolism in cancer cells will be dealt with, with a particular focus on approaches targeting defects in the mitochondrial genome.

BRCA2 (breast cancer 2, early onset) is a tumor suppressor gene that confers increased susceptibility for prostate cancer (PCa). Previous in vitro experiments demonstrated that Skp2, an E3 ubiquitin ligase aberrantly overexpressed in PCa, is involved in the proteolytic degradation of BRCA2 in PCa cells, suggesting that the BRCA2-Skp2 interaction may play a role in prostate tumorigenesis. Herein, we investigated BRCA2 and Skp2 expression during PCa development using a prostate TMA. Although luminal and basal benign prostate epithelium exhibited moderate to strong nuclear BRCA2 immunostaining, the intensity and number of positive nuclei decreased significantly in high-grade prostatic intraepithelial neoplasia and PCa. Decreased frequency and intensity of nuclear BRCA2 labeling were inversely correlated with Skp2 expression in high-grade prostatic intraepithelial neoplasia and PCa. To functionally assess the effects of BRCA2 and Skp2 expression on prostate malignant transformation, we overexpressed Skp2 in normal immortalized prostate cells. Skp2 overexpression reduced BRCA2 protein and promoted cell growth and migration. A similar phenotype was observed after reduction of BRCA2 protein levels using specific BRCA2 small-interfering RNA. Forced BRCA2 expression in Skp2-overexpressing stable transfectants inhibited the migratory and growth properties by >60%. These results show that loss of BRCA2 expression during prostate tumor development is strongly correlated with both migratory behavior and cancer growth and include Skp2 as a BRCA2 proteolytic partner in vivo.

Myeloid sarcoma is an extramedullary tumor mass composed of immature myeloid cells. Myeloid sarcoma may develop de novo, concurrently with acute myeloid leukemia (AML), or at relapse. Although myeloid sarcoma can occur at any site, myeloid sarcoma involving the heart is extremely rare. Reported here is the case of a 30-year-old man, initially diagnosed with acute promyelocytic leukemia (APL) in bone marrow, who presented later with myeloid sarcoma at multiple anatomical sites (left scapula, thoracic vertebra, right atrium, and supraclavicular mass) in multiple relapses. Conventional cytogenetic studies performed on the atrial sample revealed a karyotype with additional material on the short arm of chromosome 7, at 7p22. Fluorescence in situ hybridization studies confirmed a cryptic PML-RARA fusion on the short arm of chromosome 7, as well as a second fusion on one copy of chromosome 15. With the fourth and latest relapse, molecular cytogenetic studies performed on interphase nuclei of the myeloid sarcoma specimen (a supraclavicular mass) showed evidence of six related abnormal clones with a PML-RARA fusion, suggesting clonal evolution. This represents a rare case of APL with a cryptic PML-RARA rearrangement presenting as myeloid sarcoma at multiple relapses and involving multiple anatomical sites, including cardiac atrium

Coexistence of inv(16) and t(9;22) is a rare chromosomal aberration, one that has been described in chronic myelogenous leukemia (CML), mainly in myeloid blast crisis, and de novo acute myeloid leukemia (AML). Approximately 14 cases have been reported, including only 1 pediatric case. Here we present the case of a 13-year-old boy with a new diagnosis of AML with some features of monocytic differentiation. Conventional cytogenetic analyses on unstimulated blood showed three related abnormal clones with inv(16) in the stemline: 46,XY,inv(16)(p13.1q22)[2]/46,idem,del(7)(q22q32)[16]/46,idem,t(9;22;19)(q 34;q11.2;p13.1)[2]. Fluorescence in situ hybridization (FISH) studies on interphase nuclei and previously G-banded metaphases showed a 3'CBFB deletion and confirmed the presence of the Philadelphia chromosome in a t(9;22;19) rearrangement. Deletion 7q31 was also confirmed by interphase FISH analysis. The patient was treated with standard AML chemotherapy plus gemtuzumab as part of a clinical trial. At 10-months follow-up, he was in remission. To the best of our knowledge, this is the first description of a pediatric case of de novo AML with a stemline showing inv(16) along with 3'CBFB deletion, an abnormal clone revealing in addition a del(7)(q22q32), and another clone with a t(9;22;19)(q34;q11.2;p13.1) as an additional abnormality

Lack of estrogens affects male physiology in a number of ways, including severe changes in liver metabolism that result in lipid accumulation and massive hepatic steatosis. Here we investigated whether estrogen deficiency may alter the functionality and permeability properties of liver mitochondria using, as an experimental model, aromatase knockout (ArKO) male mice, which cannot synthesize endogenous estrogens due to a disruption of the Cyp19 gene. Liver mitochondria isolated from ArKO mice displayed increased activity of the mitochondrial respiratory complex IV compared with wild-type mice and were less prone to undergo cyclosporin A-sensitive mitochondrial permeability transition (MPT) induced by calcium loading. The altered permeability properties of the mitochondrial membranes were not due to changes in reactive oxygen species, ATP levels, or mitochondrial membrane potential but were associated with increased content of the phospholipid cardiolipin, structural component of the mitochondrial membranes and regulator of the MPT pore, and with increased mitochondrial protein levels of Bcl-2 and the adenine nucleotide translocator (ANT), regulator and component of the MPT pore, respectively. Real-time RT-PCR demonstrated increased mRNA levels for Bcl-2 and ANT2 but not for the ANT1 isoform in ArKO livers. Supplementation of 17beta-estradiol retrieved ArKO mice from massive hepatic steatosis and restored mitochondrial permeability properties, cardiolipin, Bcl-2, and ANT2 levels. Overall, our findings demonstrate an important role of estrogens in the modulation of hepatic mitochondrial function and permeability properties in males and suggest that estrogen deficiency may represent a novel positive regulator of Bcl-2 and ANT2 proteins, two inhibitors of MPT occurrence and powerful antiapoptotic molecules

An association between intravascular large B-cell lymphoma (IVLBCL) and the mixed lineage leukemia (MLL) gene has never been demonstrated. Here, we report an IVLBCL in a 47-year-old Asian man. Morphologically, the atypical lymphoid infiltrate was entirely confined in the lumina of capillaries, small vessels, and sinusoidal space. Within the kidney, the neoplastic lymphoid cells exhibited both the glomerular and peritubular capillary distribution pattern. Conventional cytogenetic analysis from the bone marrow aspirates displayed a complex karyotype, with a notable triple tandem repeat at band segment q22-q25 of chromosome 11. Fluorescence in situ hybridization with an MLL probe set, performed on both interphase cells and metaphase spreads, confirmed the presence of 3 copies of the MLL gene on the derivative chromosome 11. From this finding and 3 other IVLBCL cases reported in the literature, we conclude that MLL may play an important role in the lymphomagenesis of IVLBCL at least in a subset of cases

BRCA2 is a multifunctional tumor suppressor protein which plays critical roles in DNA repair, transcription, and cell proliferation, and the loss of which has been linked to the biology of several types of cancers. Here, on prostate adenocarcinoma specimens from 80 patients, we demonstrate that BRCA2 protein is lost in carcinoma cells compared to normal and hyperplastic prostate epithelium. Using highly metastatic prostate cancer PC-3 cells, we show that while BRCA2 depletion by small-interfering RNA promoted migration onto the extracellular matrix proteins fibronectin, laminin, and collagens, as well as invasion through the reconstituted basement membrane matrix Matrigel by more than 140%, recombinant BRCA2 overexpression decreased both phenomena by 57-80% and changed cell morphology from angular and spindle to round and compact. The BRCA2 inhibitory effect on cancer cell migration and invasion resulted from down-regulation of matrix metalloproteinase (MMP)-9 protein levels due to increased MMP-9 proteolysis, and was signaled through inhibition of PI3-kinase/AKT and activation of MAPK/ERK pathway. In BRCA2-overexpressing PC-3 cells, transient transfection with a constitutively active PI3-kinase mutant or treatment with the MAPK/ERK inhibitor PD98059 rescued MMP-9 levels and restored the migratory and invasive capabilities. Consistently, PI3-kinase inhibition with a dominant-negative mutant or MAPK/ERK activation with a gain-of-function mutant reduced MMP-9 levels and prevented migration and invasion in wild-type PC-3 cells. These results provide novel evidence showing that a functional BRCA2 protein may limit the metastatic potential of neoplastic cells by down-regulating MMP-9 production through inhibition of PI3-kinase/AKT and activation of MAPK/ERK, effectively hindering cancer cell migration and invasion

Diagnosis of myelodysplastic syndromes (MDS) could be difficult. We explored the usefulness of the enumeration of maturing B-lineage precursors (hematogones) by multiparameter flow cytometric analysis in the diagnosis of MDS in bone marrow (BM) specimens. We evaluated 111 MDS, 120 non-MDS (most with cytopenias; control group 1), and 41 noncytopenic lymphoma staging BM (control group 2) specimens. The percentage of total hematogones was significantly lower in MDS (median, 0%; mean, 0.10%) compared with non-MDS (control group 1, median, 0.38%, and mean, 0.91%; control group 2, median, 0.38%, and mean, 0.60%; P < .0001), as was the percentage of the most immature (stage I) hematogones. Thus, hematogone enumeration may serve as a biomarker to aid in the diagnosis of MDS. Interestingly, the percentage of hematogones was not significantly different between MDS subgroups or patients with MDS with and without chromosomal abnormalities, implying that a defect in maturing B-cell precursors may be an early event in the pathogenesis of MDS

Mitochondrial dysfunction resulting from mitochondrial DNA (mtDNA) mutations and/or depletion has been correlated with cancer progression and drug resistance. To investigate the role of mtDNA in prostate cancer progression, we used LNCaP and PC-3 prostate carcinoma cells as experimental model. Compared to minimally invasive androgen-dependent LNCaP cells, highly invasive androgen-independent PC-3 cells, as well as androgen-independent DU145 and C4-2 cells, exhibited significantly reduced mtDNA content. In PC-3 cells, reduction of mtDNA was accompanied by decreased mitochondrial membrane potential (DeltaPsi(m)), increased migration onto the basement membrane protein laminin-1, reduced chemosensitivity to paclitaxel (IC(50)=110 nM vs. 22 nM) and decreased expression of poly(ADP-ribose) polymerase (PARP)-1. To investigate the relationship between mtDNA depletion and these phenotypic characteristics, we established mtDNA-depleted LNCaP cells [Rho(-)] by long-term exposure to ethidium bromide or treated wild-type LNCaP cells with a mitochondrial ionophore, carbonyl cyanide m-chlorophenylhydrazone. Both manipulations resulted in DeltaPsi(m) loss, acquisition of invasive cytology, increased motility onto laminin-1, reduced sensitivity to paclitaxel (IC(50)= approximately 100 nM) and approximately 75% reduction in PARP-1 protein levels, resembling PC-3 cells. Overall, these results provide novel evidence demonstrating that mtDNA depletion in early prostate carcinoma may contribute to the acquisition of a more invasive phenotype that is less sensitive to paclitaxel-induced apoptosis