A macrophage-cell model of HIV latency reveals the unusual importance of the bromodomain axis

BACKGROUND

Although macrophages are now recognized as an essential part of the HIV latent reservoir, whether and how viral latency is established and reactivated in these cell types is poorly understood. To understand the fundamental mechanisms of viral latency in macrophages, there is an urgent need to develop latency models amenable to genetic manipulations and screening for appropriate latency-reversing agents (LRAs). Given that differentiated THP-1 cells resemble monocyte-derived macrophages in HIV replication mechanisms, we set out to establish a macrophage cell model for HIV latency using THP-1 cells.

METHODS

We created single-cell clones of THP-1 cells infected with a single copy of the dual-labeled HIVGKO in which a codon switched eGFP (csGFP) is under the control of the HIV-1 5' LTR promoter, and a monomeric Kusabira orange 2 (mKO2) under the control of cellular elongation factor one alpha promoter (EF1α). Latently infected cells are csGFP-, mKO2+, while cells with actively replicating HIV (or reactivated virus) are csGFP+,mKO2+. After sorting for latently infected cells, each of the THP-1 clones with unique integration sites for HIV was differentiated into macrophage-like cells with phorbol 12-myristate 13-acetate (PMA) and treated with established LRAs to stimulate HIV reactivation. Monocyte-derived macrophages (MDMs) harboring single copies of HIVGKO were used to confirm our findings.

RESULTS

We obtained clones of THP-1 cells with latently infected HIV with unique integration sites. When the differentiated THP-1 or primary MDMs cells were treated with various LRAs, the bromodomain inhibitors JQ1 and I-BET151 were the most potent compounds. Knockdown of BRD4, the target of JQ1, resulted in increased reactivation, thus confirming the pharmacological effect. The DYRK1A inhibitor Harmine and lipopolysaccharide (LPS) also showed significant reactivation across all three MDM donors. Remarkably, LRAs like PMA/ionomycin, bryostatin-1, and histone deacetylase inhibitors known to potently reactivate latent HIV in CD4 + T cells showed little activity in macrophages.

CONCLUSIONS

Our results indicate that this model could be used to screen for appropriate LRAs for macrophages and show that HIV latency and reactivation mechanisms in macrophages may be distinct from those of CD4 + T cells.

Beyond genomics: critical evaluation of cell line utility for ovarian cancer research

OBJECTIVE

Comparisons of The Cancer Genome Atlas (TCGA) with high grade serous ovarian cancer (HGSOC) cell lines used in research reveal that many common experimental models lack defining genomic characteristics seen in patient tumors. As cell lines exist with higher genomic fidelity to TCGA, this study aimed to evaluate the utility of these cell lines as tools for preclinical investigation.

METHODS

We compared two HGSOC cell lines with supposed high genomic fidelity to TCGA, KURAMOCHI and OVSAHO, with the most commonly cited ovarian cancer cell line, SKOV3, which has poor genomic fidelity to TCGA. The lines were analyzed for genomic alterations, in vitro performance, and growth in murine xenografts.

RESULTS

Using targeted next generation sequencing analyses, we determined that each line had a distinct mutation profile, including alterations in TP53, and copy number variation of specific genes. KURAMOCHI and OVSAHO better recapitulated serous carcinoma morphology than SKOV3. All lines expressed PAX8 and stathmin, but KURAMOCHI and OVSAHO did not express CK7. KURAMOCHI was significantly more platinum sensitive than OVSAHO and SKOV3. Unlike SKOV3, KURAMOCHI and OVSAHO engrafted poorly in subcutaneous xenografts. KURAMOCHI and OVSAHO grew best after intraperitoneal injection in SCID mice and recapitulated miliary disease while SKOV3 grew in all murine systems and formed oligometastatic disease.

CONCLUSIONS

The research utility of HGSOC cell line models requires a comprehensive assessment of genomic as well as in vitro and in vivo properties. Cell lines with closer genomic fidelity to human tumors may have limitations in performance for preclinical investigation.