Mammary Glands Possess Intrinsic Molecular Laterality and Respond Left-Right Differently to Genetic and Pharmacological Manipulation

Mammary Glands Possess Intrinsic Molecular Laterality and Respond Left-Right Differently to Genetic and Pharmacological Manipulation. (Under the direction of Ann Ramsdell) More tumors form in the left (L) breast and tumors in the right (R) breast may be more aggressive. These epidemiological findings suggest L-R differences in overall tumor biology depending on the side of tumor origin, leading to the hypothesis that mammary glands are L-R different and have discordant responses to neoplastic risk factors. Here we show that normal mammary glands are molecularly L-R different, and have more mammary stem cells (MaSCs) in the L thoracic mammary gland (TMG). In addition, MaSCs from the L and R TMGs are molecularly and functionally different in vitro and in vivo. MaSCs respond to ErbB2 and EGFR inhibition via Lapatinib treatment asymmetrically. L-side MaSCs are inhibited by Lapatinib whereas R-side MaSCs increase in self-renewal with Lapatinib treatment. MMTV-NeuTg/Tg mice overexpress the oncogene Neu also known as ErbB2 or HER2 and model HER2+ breast cancer. MMTVNeuTg/Tg mouse TMGs respond L-R discordantly to oncogene overexpression resulting in asymmetric ductal network formation and discordant gene regulation. Furthermore, MaSCs are increased asymmetrically enhancing L-side enrichment of MaSCs, and MaSC in vitro function was asynchronously effected. Additionally, when gene expression is inverted in the MMTV-NeuTg/Tg model, MaSC in vitro growth, self-renewal, and response to Lapatinib is also inverted. Inguinal mammary glands (IMGs) of the MMTV-NeuTg/Tg model show delayed molecular laterality and are less sensitive to oncogene over-expression. When WT mice are exposed to estrogen (E2) neonatally, E2 induces asymmetric ductal morphogenesis, asymmetrically reduces luminal cell differentiation, and induces an asymmetric increase in MaSCs in TMGs. IMGs of E2 treated mice have no detectable L-R differences in morphology, suggesting IMGs are not as sensitive to early E2 exposure. Lastly, L-R differences in TMG development are shown to have an embryonic origin. RXRα+/- mice with altered embryonic development have asymmetric TMG development but not IMG development. Taken together these data show that L-R differences in TMGs originate embryonically, TMGs are lateralized organs that respond to stimulus L-R differently, and TMGs are more sensitive to perturbation than IMGs. These L-R differences in MaSC populations during normal development allow for L-R different responses to neoplasia, as well as correlate with L-R differences in patient outcome and response to therapy

The Chemopreventive Effects of Protandim: Modulation of p53 Mitochondrial Translocation and Apoptosis during Skin Carcinogenesis

Protandim, a well defined dietary combination of 5 well-established medicinal plants, is known to induce endogenous antioxidant enzymes, such as manganese superoxide dismutase (MnSOD). Our previous studies have shown through the induction of various antioxidant enzymes, products of oxidative damage can be decreased. In addition, we have shown that tumor multiplicity and incidence can be decreased through the dietary administration of Protandim in the two-stage skin carcinogenesis mouse model. It has been demonstrated that cell proliferation is accommodated by cell death during DMBA/TPA treatment in the two-stage skin carcinogenesis model. Therefore, we investigated the effects of the Protandim diet on apoptosis; and proposed a novel mechanism of chemoprevention utilized by the Protandim dietary combination. Interestingly, Protandim suppressed DMBA/TPA induced cutaneous apoptosis. Recently, more attention has been focused on transcription-independent mechanisms of the tumor suppressor, p53, that mediate apoptosis. It is known that cytoplasmic p53 rapidly translocates to the mitochondria in response to pro-apoptotic stress. Our results showed that Protandim suppressed the mitochondrial translocation of p53 and mitochondrial outer membrane proteins such as Bax. We examined the levels of p53 and MnSOD expression/activity in murine skin JB6 promotion sensitive (P+) and promotion-resistant (P-) epidermal cells. Interestingly, p53 was induced only in P+ cells, not P- cells; whereas MnSOD is highly expressed in P- cells when compared to P+ cells. In addition, wild-type p53 was transfected into JB6 P- cells. We found that the introduction of wild-type p53 promoted transformation in JB6 P- cells. Our results suggest that suppression of p53 and induction of MnSOD may play an important role in the tumor suppressive activity of Protandim