Cystine/glutamate antiporter xCT deficiency reduces metastasis without impairing immune system function in breast cancer mouse models

BACKGROUND

The upregulation of antioxidant mechanisms is a common occurrence in cancer cells, as they strive to maintain balanced redox state and prevent oxidative damage. This includes the upregulation of the cystine/glutamate antiporter xCT, which plays a crucial role in protecting cancer cells from oxidative stress. Consequently, targeting xCT has become an attractive strategy for cancer treatment. However, xCT is also expressed by several types of immune cells where it has a role in proliferation and effector functions. In light of these observations, a comprehensive understanding of the specific role of xCT in the initiation and progression of cancer, as well as its potential impact on the immune system within the tumor microenvironment and the anti-tumor response, require further investigation.

METHODS

We generated xCTnull BALB/c mice to investigate the role of xCT in the immune system and xCTnull/Erbb2-transgenic BALB-neuT mice to study the role of xCT in a mammary cancer-prone model. We also used mammary cancer cells derived from BALB-neuT/xCTnull mice and xCTKO 4T1 cells to test the contribution of xCT to malignant properties in vitro and in vivo.

RESULTS

xCT depletion in BALB-neuT/xCTnull mice does not alter autochthonous tumor initiation, but tumor cells isolated from these mice display proliferation and redox balance defects in vitro. Although xCT disruption sensitizes 4T1 cells to oxidative stress, it does not prevent transplantable tumor growth, but reduces cell migration in vitro and lung metastasis in vivo. This is accompanied by an altered immune cell recruitment in the pre-metastatic niche. Finally, systemic depletion of xCT in host mice does not affect transplantable tumor growth and metastasis nor impair the proper mounting of both humoral and cellular immune responses in vivo.

CONCLUSIONS

xCT is dispensable for proper immune system function, thus supporting the safety of xCT targeting in oncology. Nevertheless, xCT is involved in several processes required for the metastatic seeding of mammary cancer cells, thus broadening the scope of xCT-targeting approaches.

Development of a VLP-Based Vaccine Displaying an xCT Extracellular Domain for the Treatment of Metastatic Breast Cancer

Metastatic breast cancer (MBC) is the leading cause of cancer death in women due to recurrence and resistance to conventional therapies. Thus, MBC represents an important unmet clinical need for new treatments. In this paper we generated a virus-like particle (VLP)-based vaccine (AX09) to inhibit de novo metastasis formation and ultimately prolong the survival of patients with MBC. To this aim, we engineered the bacteriophage MS2 VLP to display an extracellular loop of xCT, a promising therapeutic target involved in tumor progression and metastasis formation. Elevated levels of this protein are observed in a high percentage of invasive mammary ductal tumors including triple negative breast cancer (TNBC) and correlate with poor overall survival. Moreover, xCT expression is restricted to only a few normal cell types. Here, we tested AX09 in several MBC mouse models and showed that it was well-tolerated and elicited a strong antibody response against xCT. This antibody-based response resulted in the inhibition of xCT's function in vitro and reduced metastasis formation in vivo. Thus, AX09 represents a promising novel approach for MBC, and it is currently advancing to clinical development.

Lead and other metals in gestational hypertension

OBJECTIVES

To identify any effects that lead, calcium, magnesium, and zinc may have on the development of gestational hypertension.

METHODS

Third-trimester 110 normotensive and 33 gestational hypertension cases were assayed for various metal levels, using standard techniques, including atomic absorption spectrometry.

RESULTS

Gestational hypertension cases showed significantly higher blood lead levels than normotensives. No differences were noticed regarding calcium (ionized and total), magnesium, and zinc levels. Blood lead was significantly related with blood pressure, even after correcting for the body mass indices and age. Blood pressure levels showed no relation to the other analyzed metals. However, the lead:ionized calcium ratio showed a stronger association with blood pressure, than lead alone. Blood lead showed a significant negative relationship with ionized calcium, but none with the other metals.

CONCLUSIONS

Blood lead evidently influenced blood pressure increments and gestational hypertension development. This implies that all efforts should be made to reduce the population's exposure.

Suprapubic prostatectomy combined with vesico-urethroplasty

A new look at the operation of suprapublic prostatectomy is suggested in view of the continuing substantial morbidity associated with traditional techniques. The proposition is that a reconstructive as distinct from a simple ablative operation is possible, notwithstanding long-standing beliefs to the contrary. The writer goes on to outline the principles, and to describe and illustrate in detail the steps in a new technique of prostatectomy combined with a urethroplasty, which uses full-thickness bladder wall flaps to provide immediate epithelial cover for the denuded surfaces of the prostatic urethra. The theoretical advantages of such a technique are borne out by the results in the first 400 cases so treated, which are contrasted with those from a comparable personal series of 200 retropubic prostatectomies and other representative series.

Hydrogen ion transport in the rabbit esophagus

The lumen of the rabbit esophagus was perfused in vivo with solutions (one solution per esophagus) containing 0-160 mM HCl by a constant circulation technique for 5 h. During the 1st h, net H+ flux out of the lumen (efflux) was minimal at H+ concentrations of 80 mM or less, but increased linearly with increase in luminal H+ concentrations above 80 mM. After 3 h, the net H+ efflux increased proprtionately to increasing H+ concentrations above a threshold of 20 mM. At the 5th h a linear relationship between net H+ efflux and luminal concentration was seen at all concentrations. Histological damage accompanied increase in H+ efflux and correlated with luminal acid concentrations and duration of exposure. We conclude that the rabbit esophageal mucosa is essentially impermeable to H+ below a threshold concentration of 80 mM for up to 1 h of exposure. When exposure is prolonged, this threshold steadily decreases with time. The occurrence of passive H+ diffusion above threshold concentrations most probably results from an increase in mucosal permeability, possibly an initiating event in the genesis of esophagitis.