Specific inhibition of the classical complement pathway with an engineered single-chain Fv to C1q globular heads decreases complement activation by apoptotic cells.

Apoptotic cells are potent complement activators; and proposed mechanisms include IgM-mediated classical pathway activation, C-reactive protein (CRP)-mediated classical pathway activation, and IgM-mediated lectin pathway activation. While complement activation is beneficial in clearing apoptotic cells, the resulting complement-mediated inflammation may extend damage to the surrounding cells and tissues, as observed in ischemia/reperfusion injury. We previously engineered and characterized a single-chain Fv against C1q globular heads (scFv(QuVHVL)) that blocked C1q binding to immobilized IgG and to IgG-sensitized cells, and thereby inhibited IgG-mediated classical pathway activation [Hwang H.

Complement C1q activates tumor suppressor WWOX to induce apoptosis in prostate cancer cells.

Background: Tissue exudates contain low levels of serum complement proteins, and their regulatory effects on prostate cancer progression are largely unknown. We examined specific serum complement components in coordinating the activation of tumor suppressors p53 and WWOX (also named FOR or WOX1) and kinases ERK, JNK1 and STAT3 in human prostate DU145 cells.

Methodology/principal Findings: DU145 cells were cultured overnight in 1% normal human serum, or in human serum depleted of an indicated complement protein.

Highly specific inhibition of C1q globular-head binding to human IgG: a novel approach to control and regulate the classical complement pathway using an engineered single chain antibody variable fragment.

We sought to specifically regulate the binding of human C1q, and thus the activation of the first complement component, via the construction of a single chain antibody variable binding region fragment (scFv) targeting the C1q globular heads. Here we describe details of the construction, expression and evaluation of this scFv, which was derived from a high-affinity hybridoma (Qu) specific for the C1q globular heads. The scFv was comprised of the Qu variable heavy chain domain (VH) linked to the Qu variable light chain domain (VL) and was termed scFv-QuVHVL.

Complement susceptibility in glutamine deprived breast cancer cells.

Background: Membrane complement regulatory proteins (mCRPs) inhibit complement-mediated killing of human cells by human complement, a property that confers protection from complement to malignant breast cancer cells and that thwarts some immunotherapies. Metabolic mechanisms may come into play in protecting cancer cells from the complement system subsequent to relatively low levels of complement deposition.

Results: In differentiating these mechanisms, two types of human breast cancer cell lines, MCF7 (adenocarcinoma) and Bcap37 (medullary carcinoma) were cell-cycle synchronized using glutamine-deprivation followed by restoration.

Conformationally altered hyaluronan restricts complement classical pathway activation by binding to C1q, C1r, C1s, C2, C5 and C9, and suppresses WOX1 expression in prostate DU145 cells.

Linear non-sulfated hyaluronan (HA) does not bind complement proteins yet inhibits their hemolytic function. We have previously induced the complement inhibitory function of HA by heat treatment. However, heated HA readily loses its anti-complementary activity probably due to instantaneous interchain re-association.