Therapeutic options for lymphangioleiomyomatosis (LAM): where we are and where we are going

Lymphangioleiomyomatosis (LAM), a multisystem disease affecting predominantly premenopausal and middle-aged women, causes progressive respiratory failure due to cystic lung destruction and is associated with lymphatic and kidney tumors. In the past, the treatment of LAM comprised exclusively anti-estrogen and related hormonal therapies. These treatments, however, have not been proven effective. In this article, we discuss new findings regarding the molecular mechanisms involved in the regulation of LAM cell growth, which may offer opportunities to develop effective and targeted therapeutic agents

Osteoprotegerin Contributes to the Metastatic Potential of Cells with a Dysfunctional TSC2 Tumor-Suppressor Gene

In addition to its effects on bone metabolism, osteoprotegerin (OPG), a soluble member of the tumor necrosis factor family of receptors, promotes smooth muscle cell proliferation and migration and may act as a survival factor for tumor cells. We hypothesized that these cellular mechanisms of OPG may be involved in the growth and proliferation of lymphangioleiomyomatosis (LAM) cells, abnormal smooth muscle-like cells with mutations in one of the tuberous sclerosis complex tumor-suppressor genes (TSC1/TSC2) that cause LAM, a multisystem disease characterized by cystic lung destruction, lymphatic infiltration, and abdominal tumors. Herein, we show that OPG stimulated proliferation of cells cultured from explanted LAM lungs, and selectively induced migration of LAM cells identified by the loss of heterozygosity for TSC2. Consistent with these observations, cells with TSC2 loss of heterozygosity expressed the OPG receptors, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules showed reactivities to antibodies to tumor necrosis factor–related apoptosis-inducing ligand, receptor activator of NF-κB ligand, syndecan-1, and syndecan-2. LAM lung nodules also produced OPG, as shown by expression of OPG mRNA and colocalization of reactivities to anti-OPG and anti-gp100 (HMB45) antibodies in LAM lung nodules. Serum OPG was significantly higher in LAM patients than in normal volunteers. Based on these data, it appears that OPG may have tumor-promoting roles in the pathogenesis of lymphangioleiomyomatosis, perhaps acting as both autocrine and paracrine factors

Incorporation of Uracil into Viral DNA Correlates with Reduced Replication of EIAV in Macrophages

AbstractThe retrovirus equine infectious anemia virus (EIAV) encodes a dUTPase situated between reverse transcriptase and integrase. We have described the Inability of EIAV with a 270-bp dUTPase deletion, ΔDU EIAV, to replicate to wild-type (WT) levels in equine macrophages (D. S. Threadgill, W K. Steagall, M. T. Flaherty, F. J. Fuller, S. T. Perry, K. E. Rushlow, S. F. J. LeGrice, and S. L. Payne, J. Virol. 67, 2592-2600, 1993). Here we describe the construction of a second dUTPase-deficient virus (DUD71E) containing a single amino acid substitution in dUTPase. ΔDU and DUD71E replicate to 2% of WT levels in macrophages by 7 days postinfection, when WT EIAV is highly cytopathic. To identify the replication block(s), we analyzed DNA synthesis, integration, and transcription. DNA synthesis was normal in macrophages, with evidence of full-length viral DNA by 24 hr postinfection. The level of integrated ΔDU and DUD71E DNA appeared to be decreased 2- to 3-fold compared to WT. Steady-state levels of full-length viral transcripts were decreased over 100-fold, indicating that replication of dUTPase-deficient EIAV is blocked between vital DNA synthesis and transcription. As dUTP hydrolysis normally plays a role in preventing incorporation of uracil into newly synthesized DNA, we investigated the possibility that dUTPase-deficient EIAV DNA contains uracil. In vitro assays showed that while WT virions do not utilize dUTP, dUTPase-deficient virus and recombinant RT synthesize uracil-containing DNA. The presence of uracil in viral DNA recovered from ΔDU- and DUD71E-infected macrophages was also demonstrated. In macrophages, a virally encoded dUTPase may be necessary to prevent the incorporation of uracil into vital DNA